Procedures for the Use of Risk Assessment under Part XV.1 of the Environmental Protection Act

Ontario Ministry of the Environment and Climate Change
Standards Development Branch

Glossary

Absorption

means the process by which a chemical crosses a biological boundary (for example, skin, lung, gastrointestinal tract) and enters the circulatory system following ingestion, inhalation or dermal contact.

Absorbed dose

means the amount of a substance that crosses an exposed organism’s biological boundaries (for example, skin, lung, gastrointestinal tract, root membrane). The term is synonymous with uptake and for human receptors, is expressed as milligram of chemical per kilogram of body weight per day (or mg/kg bw-day).

Bioassay

means a test (assay) in which one or more characteristics of a substance (for example potency) is measured by the response of living organisms or isolated tissues, in the present context is synonymous with toxicity test.

Bioavailability

means the fraction of an administered dose, typically oral or inhaled, that can cross a biological boundary and enter the systemic or circulatory system (expressed as a unitless value).

Carcinogen

means any substance that can cause cancer in living organisms (in the present context including animals or humans).

CCME

means the Canadian Council of Ministers of the Environment.

Chronic Daily Intake

means the amount of a chemical (usually expressed as mg/kg bw-day) to which a person is exposed on a daily basis over an extended period of time, (for example 70 years for a carcinogen) (usually expressed as mg/kg bw-day).

Complete exposure pathway

means an exposure pathway that does not have any natural or man-made barriers that prevents a receptor from being exposed to a contaminant.

Contaminants of Concern (COC)

means contaminants that have been identified in Phase I and/or detected in Phase II environmental site assessments, including possible toxic metabolites, at concentrations which exceed relevant site condition standards, or for which there are no relevant site condition standards, and including those for which the analytical method used resulted in detection limits that exceed relevant site condition standards.

CPU

means a certificate of property use referred to in Section 168.6 of the EPA.

Delivered target dose

means the amount of a substance that crosses the biological boundaries of an organism (for example skin, gastrointestinal epithelium) and becomes available for interaction at the target tissue(s) or organ(s).

Dioxin-like

means any of three families of polycyclic compounds known chemically as chlorinated dibenzo-p-dioxins, chlorinated dibenzofurans or co-planar PCBs with comparable structural and biochemical properties.

Detailed Quantitative Ecological Risk Assessment (DQ-ERA)

means a detailed risk assessment as described in 1997 CCME document entitled "A Framework for Ecological Risk Assessment" and is likely to include toxicity tests and/or biological field studies.

Dose

means the actual quantity of a chemical administered to a receptor or to which it is exposed (see delivered target dose).

Ecological receptor

means a non-human organism identified as potentially experiencing adverse impacts from exposure to a contaminant, either directly through contact or indirectly through food chain transfer.

EPA

means the Environmental Protection Act, R.S.O. 1990 c. E-19.

Ecological Risk Assessment (ERA)

means a component of a risk assessment that evaluates the likelihood that adverse ecological effects may occur, or are occurring, as a result of exposure to contaminant(s).

Endpoint

means an effect on a human or ecological receptor that can be measured or modeled and described in some quantitative fashion.

ESA

means environmental site assessment.

Exposure assessment

means the qualitative or quantitative determination or estimation of the magnitude, frequency, duration and routes of exposure for the contaminant, including assessment of the uncertainties associated with the determination.

Exposure pathway

means the physical course/route a contaminant takes from its source of the receptor of concern.

Exposure point concentration

means the concentration in an environmental medium (soil, water, air, sediment) to which a human or ecological receptor is presumed to be exposed.

HEAST

means Health Effects Assessment Summary Table published by the United States Environmental Protection Agency.

Human Health Risk Assessment (HHRA)

means a component of a risk assessment that characterizes the nature and magnitude of risks to human health from exposure to contaminants.

Hazard

means the potential of a contaminant to cause harm to an individual, population or the natural environment. Hazard may refer either to the contaminant itself or the adverse impact that the contaminant causes.

Hazard quotient

means the ratio of a single substance exposure level (for example, dose) over a specified period of time to a toxicity reference value (TRV) such as RfD or RfC or RsD or RsC or TDI) for that substance derived from similar exposure characteristics (for example, duration, frequency, route, etc.).

Incomplete exposure pathway

means an exposure pathway where natural or man-made barriers effectively prevent a receptor from being exposed to a contaminant.

Intake

means the actual quantity of a chemical administered to an organism or to which it is exposed. Also defined as potential dose, it is expressed as mg/kg bw-day.

IRIS

means the Integrated Risk Information System, a database of human health effects that may result from exposure to various contaminants found in the environment, maintained by the United States Environmental Protection Agency.

Local background

means the ambient concentration of a contaminant in the soil, ground water, air or sediment in the local environment that is representative or typical of the conditions in an urban or rural setting. Local background concentrations result from either chemicals that occur naturally in the environment or chemicals that are emitted by anthropogenic activities other than from activities being carried out on the property being assessed.

Limited scope risk assessment (LSRA)

means a risk assessment completed in accordance with section 7 of Schedule C in O. Reg. 153/04.

Ministry

means the Ontario Ministry of the Environment.

Natural environment

means the air, land and water, or any combination or part thereof, of the Province of Ontario.

Natural local background concentration risk assessment (NLBRA)

means a risk assessment completed in accordance with section 8 of Schedule C in O. Reg 153/04. New science risk assessment (NSRA) means a risk assessment completed in accordance with section 9 of Schedule C in O. Reg. 153/04.

Occupational Exposure Limits (OEL)

means a general term for limits set for workers exposure, expressed as a time-weighted average concentration (mg/m³) for a conventional 8-hr workday and a 40-hr workweek.

On-site

means located on the RA property which is owned by the RA property owner who submitted the risk assessment pre-submission form.

Off-site

means located off the RA property, but with implications for the property under assessment.

PAHs

means polycyclic aromatic hydrocarbon.

PCB

means polychlorinated biphenyls.

Preliminary Quantitative Ecological Risk Assessment (PQ-ERA)

means preliminary quantitative risk assessment as described in 1997 CCME document entitled "A Framework for Ecological Risk Assessment" is an intermediate level of quantitative risk estimation for specific VECs exposed to the contaminants of concern.

Phase one ESA

means a phase one environmental site assessment as defined in section 168.1 of the EPA.

Phase two ESA

means a phase two environmental site assessment as defined in section 168.1 of the EPA.

Pre-Submission Form (PSF)

means a form that includes a description of the RA property and property ownership, lists the contaminants of concern, potential receptors; transport and exposure pathways described in the conceptual site model and provides a proposal for proceeding with the risk assessment.

Property specific standard

means a soil, ground water or sediment standard specified in a risk assessment which has been conducted according to the RSC Regulation and accepted by the Director under section 168.5 of the EPA.

Public communication

means the process of communication that promotes discussion between the RA property owner and the public, and provides the public with the opportunity to discuss the decisions of the owner.

Public Domain

in the context of this document means 'freeware' RA models that can be downloaded from agency sites. QA/QC means quality assurance/quality control.

QP

means qualified person.

QP_ESA

means qualified person who is responsible for the supervision of or conducting the environmental site assessment for the purposes of section 168.1 of the EPA as set out in subsection 5 of the RSC Regulation.

QP_RA

means qualified person who is responsible for conducting or supervising the risk assessment for the purposes of section 168.1 of the EPA as set out in subsection 6 of the RSC Regulation. RA means risk assessment.

Receptor

means an organism, person, population or community that is exposed to contaminant(s).

Record of Site Condition

means a document prepared in accordance with Part XV.1 of the EPA and regulations there under, that includes a summary of the final environmental condition of a property.

Reference concentration

refers to a concentration of a compound in a media to which chronic (i.e. lifetime) exposure is not expected to cause adverse effects to an organism.

Reference dose

means an estimate of a chronic daily exposure to the general human population, including sensitive sub-groups, that is likely to be without an appreciable risk of harmful effects during a lifetime of exposure; expressed as mg/kg bw-day.

Relative Absorption Factor (also known as relative bioavailability adjustment)

is the fraction obtained by dividing the absolute bioavailability of a chemical present in the environmental media by the absolute bioavailability of that same chemical present in the dosing medium used in the toxicity study from which the reference dose for human health risk assessment was determined.

Relative bioavailability

is a measure of the difference in extent of absorption among two or more forms of the same chemical (for example, lead carbonate vs. lead acetate), different media (for example, food, soil, water), or different doses. In the context of environmental risk assessment, relative bioavailability is the ratio of the absorbed fraction from the exposure medium in the risk assessment (for example, soil) to the absorbed fraction from the dosing medium used in the critical toxicity study.

Reasonable Maximum Exposure (RME)

means the highest exposure that is reasonably expected to occur on a site. The objective of the RME is to estimate a conservative exposure scenario (i.e., well above the average scenario, typically the 95^th percentile) that is within the range of likely exposure.

Remediation

means the management of contaminants at a property to prevent, minimize or mitigate damage to human health or the natural environment, so that it is acceptable for its intended use. In the context of this document, remediation can include, without limitation, removal, destruction and containment of toxic substances.

Remedial work plan

means a plan to bring about the remediation of the property.

RfC

See reference concentration.

RfD

See reference dose.

Risk management

means the implementation of a strategy or measures to control or reduce the level of risk estimated by the risk assessment to prevent, eliminate or ameliorate any adverse effect on the property.

RSC Regulation

means Ontario Regulation 153/04, as amended.

RsC

means risk specific concentration: the concentration of a contaminant (expressed in units of µg/m³) corresponding to a specified level of lifetime risk (for example, 10⁻⁶).

RsD

means risk specific dose: the dose of a contaminant (expressed in units of mg/kg bw-day) corresponding to a specified level of a lifetime risk (for example, 10⁻⁶).

Screening Level Ecological Risk Assessment (SL-ERA)

means a primarily qualitative or a semi-quantitative screening assessment, as described in the 1997 CCME document entitled "A Framework for Ecological Risk Assessment", of the potential environmental risk to specific ecological receptors that have been determined to be of importance.

Site condition standards

means site condition standards as they are defined in the RSC Regulation.

Slope factor

means the upper bound estimate of cancer risk per mass of a contaminant contracted per unit body weight per day, expressed in units of (mg/kg bw-day)⁻¹.

Site plan when included in a risk assessment report,

means a diagram of the RA property indicating building locations and contaminant or source area distribution.

Threshold

means the concentration or dose of a contaminant below which an adverse impact is not expected to occur.

Tolerable Daily Intake (TDI)

means an estimate (with uncertainty spanning about an order of magnitude) of the amount of a contaminant, generally expressed on a body weight basis (mg/kg bw-day) that can be ingested daily over a lifetime without appreciable health effects.

Toxicity test

means the determination of the effect of a contaminant on a group of selected organisms, under defined conditions. An environmental toxicity test may measure the proportion of organisms affected and/or the degree of effect shown, after exposure to a whole test soil sample (i.e., undiluted property soil) or a test soil sediment or water in specific concentrations.

Uptake

means in exposure assessment, the amount of a contaminant crossing the biological boundaries (for example, skin, lung, gastrointestinal tract) of an organism and reaching the systemic circulation. The term is synonymous with absorbed dose.

Valued Ecosystem Components (VECs)

means specific ecological receptors (species or habitats) that have been determined to be of ecological importance at the site in question considering the current and proposed land use.

Wider area of abatement risk assessment (WAARA)

means a risk assessment completed in accordance with section 10 of Schedule C in O. Reg. 153/04.

Percentile (90^th, 95^th)

describes sample data frequency distribution such that 90^th or 95^th % of the data distribution is below that value and 10 or 5 % of the data distribution is above that value.

95% UCL for the mean

means the 95 % Upper Confidence Limit (95% UCL) for a mean and is defined as a value that, when repeatedly calculated for randomly drawn subsets of size "n", equals or exceeds the true mean 95% of the time. The 95% UCL provides a measure of the uncertainty of the mean.

Introduction

This Procedure document contains plain language guidance on how to conduct risk assessment work and draft a risk assessment report for submission to the Ministry of the Environment (the ministry) under section 168.5 of the Environmental Protection Act (EPA) and Schedule C in Ontario Regulation 153/04 Records of Site Condition (RSC) (the RSC Regulation). The RSC Regulation governs the preparation of risk assessment in Ontario for chemical contaminants in support of the submission of a Record of Site Condition for an individual property. Risk assessment reports must comply with the mandatory requirements specified in Section 4 of Schedule C (Table 1). References to the RSC Regulation and the EPA and exact quotes, taken from Schedule C are provided which identify the mandatory requirements for all risk assessment reports and identify the characteristics of risk assessments that may use alternate procedures and be subject to alternate time lines. However, stakeholders are still required to understand what is in the legislation and regulations and where necessary, seek legal counsel. Stakeholders should ensure that they refer to the most recent version of this document and any amendments to the RSC Regulation or Act.

Where the guidance document refers to mandatory requirements for risk assessment reports, as set out in regulation, these actions are signified by the word "must". Failure to meet these mandatory requirements means that the risk assessment work undertaken and the subsequent risk assessment report will not be considered by the ministry to be completed in accordance with the RSC Regulation. Where the guidance document indicates that something "should" be done, this is an expression of what the ministry considers to be a best practice. If the best practice is not undertaken, it is advisable that the reasons why the best practice was not followed be set out in the risk assessment report. It is the discretion of the approving Director to determine whether, and to what extent, best practices have been met, and whether to accept the risk assessment report, under Section 168.5 of the Environmental Protection Act.

This Procedure document provides the minimum requirements for conducting both the human health and ecological components of risk assessment for contaminated properties. It is not a comprehensive description of the risk assessment approach required for every potential contaminant situation or site condition. Since site conditions differ at each property and decisions may have to be made that are unique to existing circumstances, some risk assessment options are provided. Sound scientific judgment should be exercised throughout the risk assessment, however, in all cases.

In general, this Procedure document does not provide details for biological or hydrogeological monitoring, or epidemiological studies or address all activities required for the design of community-based or area-wide risk assessment studies.

This Procedure document is intended for use by experienced risk assessors in conjunction with best professional judgment. Additional information sources are provided at the end of this Procedure document for reference purposes.

Section 1. Initiating the Risk Assessment

1.1 Background to Risk Assessment

Risk, in the context of environmental risk assessment, is a measure of the probability that a hazard will cause harm to an individual, population or the natural environment under defined conditions of exposure to a contaminant. Risk assessment is the scientific examination of the nature and magnitude of risk. It is a scientific process used to describe and estimate the likelihood of adverse health effects resulting from exposure of both human and ecological receptors to environmental contaminant(s).

Human health risk assessment (HHRA) is the evaluation of the risk of adverse health effects, and the accompanying uncertainties, to humans caused by exposure to a contaminant at a given property. Ecological risk assessment (ERA) is a process that evaluates the risk that adverse ecological effects may occur, or are occurring, as a result of exposure to contaminant(s). Both assessments take into consideration that many contaminants may be present simultaneously in several media such as food, air, water, soil, dust and/or consumer products, and that these contaminants reach receptors through multiple exposure pathways.

Since property-specific characteristics are incorporated into risk assessment, there can be numerical differences between the published ministry site condition standards and the property specific standards developed through risk assessment. The level of risk afforded by property specific standards derived through risk assessment is intended to be the same as the target level of risk for any of the site condition standards published in the document Soil, Ground Water and Sediment Standards for Use Under Part XV.1 of the Environmental Protection Act (site condition standards). The main difference is that under a risk assessment, many of the input variables to the risk assessment process are determined for the specific property. Some of the conservative assumptions utilized in the setting of the generic site condition standards are not required to meet the target risk level and are replaced with property-specific values.

Risk assessment can often lead to recommendations to utilize risk management to provide protection to human health and the environment. In this situation, risk management measures must be maintained to achieve the same target level of risk as the site conditions standards. Risk management is a process which is distinct and separate from other components of risk assessment, by which measures to control or reduce the level of risk estimated by the risk assessment are developed and implemented. Risk management integrates the results from the other components of risk assessment with information about technical resources, socio-economic factors and control options in order to reach decisions about the best way to manage a property. It is important that the HHRA and ERA components of risk assessment are clearly separated from the risk management component so that risk managers have scientifically based risk estimates upon which to base risk management decisions.

1.2 When to Consider Risk Assessment

For the purpose of this Procedure document, risk assessment is a process for estimating the likelihood of adverse effects that could arise from the presence of contaminants of concern (COCs) and exposure pathways to human and ecological receptors at a contaminated property. As such, information derived from conducting a risk assessment is used to determine the standard for each COC that may be applied when filing a RSC for a property under section 168.4 of the EPA and referred to as a property specific standard. The risk assessment process can also help risk managers evaluate and compare the effectiveness of remediation and risk management alternatives for a specific property.

Risk assessment principles have been utilized in the generic process which the ministry used to develop the site condition standards. The site condition standards are applicable at the majority of situations encountered at a contaminated site but may not always be appropriate for situations where property-specific considerations deviate substantially from the conditions assumed in the ministry generic process used to develop the site condition standards.

If the risk assessment approach is considered as an alternative to using the site condition standards in order to account for property specific considerations, the property owner should be advised of the recommendations of this Procedure document and the potential limitations associated with the risk assessment approach. Based on the level of effort required to assess risk for COCs on some properties it may be preferable to remediate the property to the site condition standards.

The RSC Regulation Part IX Site Condition Standards and Risk Assessments should be referred to when considering if the risk assessment approach is appropriate.

When considering potential COCs refer to the following sections of the RSC Regulation;

• Schedule C Part I Mandatory Requirements
  • Section 3 Contaminants of Concern.

Further clarification relating to contaminants detected on the site for which there are no site condition standards is provided in the RSC Regulation;

• Section 43 Applicable Site Condition Standards "N/A", "N/V" or not listed.

The following sections of the RSC Regulation should also be referred to when considering what approach might be taken to the risk assessment;

• Section 44 Risk Assessment Form
• Schedule C Part I Mandatory Requirements
  • Section 1 Definitions and
  • Section 2 Components of a Risk Assessment and
• Schedule C Part II Alternative Risk Assessment Procedures.

In the initiation stages of a risk assessment reference should be made to the following sections of the RSC Regulation;

• Schedule C Part I Mandatory Requirements
  • Section 3 Mandatory Requirements of a Pre-Submission Form

• Schedule C Table 1
  • Report Section 2 Risk Assessment Team
  • Report Section 8 Public Communication Plan

Additional guidance on meeting the requirements of these sections is provided below.

1.3 Role and Responsibilities of the Risk Assessment Qualified Person

A risk assessment must be conducted by a qualified risk assessment team under the supervision of a Qualified Person (QP_RA). The qualifications associated with the QP_RA are specified in the RSC Regulation. A resume for the QP_RA and each team technical lead are to be provided in an Appendix to the risk assessment report.

As part of the process of submitting a Pre-Submission Form (PSF), the QP_RA will self-declare the qualifications set out in the RSC Regulation by attaching a post secondary education transcript and work references. Once these qualifications have been submitted to the ministry via a previous PSF they may not be required again.

1.3.1 Making Certified Statements

The QP_RA must make the certified statements verbatim as set out in Schedule C, Part I, Section 5 "Mandatory Certifications" of the RSC Regulation.

1.3.2 Formation of Risk Assessment Team

In addition, the QP_RA must identify the technical leads for the RA team and demonstrate that the team represents all of the required/relevant disciplines to complete the RA. If a technical lead for a specific discipline is absent from the RA team, the QP_RA must explain why that particular discipline is not required for the completion of the RA. The minimum requirements for the risk assessment team are provided in Table 1 of the RSC Regulation, Schedule C, and reproduced below.

Risk assessment team technical leads should be identified in the Pre-Submission Form and the Risk Assessment Report for each of;

• Human Health Risk Assessment
• Ecological Risk Assessment
• Hydrogeology
• Engineering (if risk management is required)

The following areas of expertise are normally associated with completion of a RA. A particular risk assessment team should generally cover all areas of academic expertise listed below, but may vary depending on the project. Several areas of expertise may be covered by a single team member, and team members' expertise may overlap, however all areas should be covered by the team as a whole.

Educational qualifications for individual risk assessment team technical leads should include a specialized post-secondary education equivalent to a four-year degree level in one or more of the following areas:

• Human and/or mammalian toxicology
• Ecotoxicology (aquatic and terrestrial)
• Geology/hydrogeology
• Soil science/soil chemistry
• Environmental science
• Environmental chemistry
• Analytical chemistry
• Engineering

One or more team members also should have work experience in one or more of the following:

• Contaminated land assessment
• Environmental sampling, including soil sampling design and methodology
• Ground water sampling design and methodology
• Surface water and sediment sampling and design
• Biota assessment, including sampling and bioassay
• Interpretation of analytical data and QA/QC procedures
• Assessment of contaminant exposure pathways and risk
• Contaminant fate and transport in the environment
• Exposure assessment
• Data evaluation/statistical analysis
• Toxicity evaluation (including hazard and dose-response assessment)
• Risk evaluation
• Remediation technologies

1.4 Preparation for Conducting a Risk Assessment

Risk assessment, in the context of Part XV.1of the Environmental Protection Act (EPA), is used to establish risk-based standards for a property and may include risk management measures. A risk assessment is built upon the results of a Phase one ESA and the extensive sampling, analytical work, hydrogeology and other elements of property characterization done in a Phase two ESA. The Phase one and Phase two ESAs must be conducted according to the requirements described in Parts VI, VII and VIII of the RSC Regulation. Any analytical results to be relied upon in the risk assessment must meet the requirements of Part IX Section 47 of the RSC Regulation.

To clarify, the ministry is fully supportive of the use of novel and innovative techniques to investigate environmental contamination, identify contaminant sources and extent and develop a conceptual site model in a cost effective and timely manner. Analytical results which are critical to support the assumptions in the risk assessment, however, must be confirmed using methods which comply with Section 47 of the RSC Regulation. As an example, field-portable analytical devices such as photoionization detectors, portable gas chromatographs and x-ray fluorescence detectors can be effective tools to identify appropriate locations for collection of samples to be analyzed in compliance with the RSC Regulation and relied upon in the risk assessment. Similarly, data from older site assessments which do not comply with the RSC Regulation can be used to identify where confirmatory analysis is required. Both compliant analysis and background supporting studies should be summarized in the risk assessment report.

The core of the risk assessment is a risk evaluation based upon toxicology, exposure assessment and characterization of ecological and human receptors and exposure pathways, as described in this Procedure document. The inter-relationship between a Phase one ESA, or Phase two ESA, and risk assessment is illustrated in Figure 1: Flowchart for the Site Remediation Process with Risk Assessment, shown in Section 8 of this Procedure document.

1.4.1 Pre-Submission Form

As the first stage of conducting a risk assessment, a Pre-Submission Form (PSF) must be submitted by the RA property owner to the ministry for review in advance of the RA report. Conducting a risk assessment now includes compiling property characterization and receptor characterization information in the PSF. The QP_RA should develop the PSF with a team of experts who possess the expertise required to address all exposure pathways and receptors of potential concern.

The PSF provides an opportunity to confirm with the ministry that the risk assessment approach and general scope as described in both narrative and visual forms (conceptual site model) are appropriate for the site and contaminants being considered.

The QP_RA must prepare the PSF for the property owner, based on the results of the Phase one ESA, and Phase two ESA and any other information that the QP_RA considers relevant. The ministry will prepare a letter of response that indicates the review timeline required for the RA approach, as well as comments concerning the scope of the RA. The purpose of the PSF is to:

• Identify the RA property and ownership;
• Identify the risk assessment team technical leads and self declaration of the QP_RA;
• Confirm that a Phase one ESA and Phase two ESA have been conducted as prescribed by the RSC Regulation;
• Provide the proposed scope of the risk assessment including a preliminary conceptual site model and hazard identification of the RA property by:
  • Describing the RA property setting, contaminant sources, potential COCs, transport pathways, exposure pathways (including the results of any screening level assessment, if performed), and human and ecological receptors,
  • Including a summary of key data that supports the conceptual model,
  • Proposing the collection of additional data, if required, and
  • Proposing an approach for proceeding with the risk assessment that will determine the timeline for risk assessment review.

The PSF provides the ministry with a general view on the approach to the risk assessment and the risk assessment team at an early stage.

The PSF process is intended to improve the quality of risk assessment submissions when they are made to the ministry at the end of the risk assessment process. The outcome of this preliminary consultation is not binding on the RA property owner or the ministry, as the understanding of site conditions may develop and/or change during the course of the risk assessment. For this reason, the ministry comment on the PSF does not in any way indicate acceptance of the final risk assessment approach or other conclusions or acceptance of the risk assessment report by the Director pursuant to s. 168.5 of the EPA.

Requirements for submission of a Pre-Submission form (PSF) are specified in the RSC Regulation in Section 3 of Schedule C. A form containing much of the information required by the RSC Regulation is provided in Appendix D of this Procedures document. The remaining information is to be provided as drawings with explanatory notes (text). The PSF must be accompanied by a site plan and conceptual site model diagrams as described in the RSC Regulation. Explanatory notes should be provided to the extent necessary for the reader to understand the hazards, transport and exposure pathways, receptors and key site data on which the risk assessment approach is based, and including the rationale for why receptors will or will not be exposed to the contaminated media, with and without risk management, and the type of risk management which is contemplated. Guidance for completion of the form is provided in the Technical Update "Preparation and submission of a Pre-Submission Form for a risk assessment to be submitted under the new Record of Site Condition Regulation (O. Reg. 153/04)". The form and the Technical Update are available on the ministry’s Brownfields webpage.

If, at any time after submitting the PSF, the qualified person responsible for the preparation of the risk assessment changes or the property owner changes, the property owner shall give notice to the Director of the change in circumstance.

Key to the success of obtaining useful ministry comment is the clear description in the PSF of the proposed conceptual site model. The complete requirements of the RSC Regulation with respect to the PSF form and attached drawings are in Schedule C Section 3. Subsections (8) and (9), which specifically relate to the required content of a conceptual site model, are copied in the text box below;

If a risk assessment is to be submitted to support a naturally elevated background concentration as a property specific standard, the requirements of a PSF relating to human and ecological receptors and exposure pathways do not apply. Provisions relating to a PSF for this purpose are included in Schedule C Section 3 (10) and are copied in the text box below. In these cases, the site plan and cross sections of the property are intended to convey the rationale for attributing elevated concentrations to natural geological features and to support and describe the planned sampling program to meet Schedule C subsections 8(4) to (9).

Further explanation regarding the description of the conceptual site model are provided below.

PSF Preparation Requirements - Drawings

The PSF is comprised of a completed form and attached drawings. Drawings that support and elaborate on the content of the form are to include a scale site plan, one or more cross-sections of the property and other line drawings, including pictures, line art, flow diagrams, text and tabulated data at the discretion of the proponent and QP.

The goal of the drawings is to provide a three dimensional illustration (site area and depth) of the subsurface hydrogeological conditions, contaminant sources, extent of contamination, transport pathways, receptors and routes of exposure which, together, comprise a preliminary conceptual site model. The soil layers and groundwater units identified on the PSF should be clearly identified in the drawing(s). Combined with the information provided in the form, the drawings are intended to convey to the ministry the risk assessment team’s current understanding of the types and location of hazards, potential exposure pathways and barriers within pathways, and the type and location of potential receptors consistent with the proposed land use. Sufficient site information data should be provided to determine if there is adequate knowledge of the site on which to base a risk assessment consistent with the illustrated conceptual site model and the planned risk assessment approach.

It is suggested that a location map showing the property in context to the local neighbourhood and adjacent land uses be included.

The proponent should include with the PSF any additional supporting information, which may not be site-specific or compliant with the regulation but which they believe provides additional information to support the proposed risk assessment as well as any plans for the collection of additional information.

In developing and illustrating a conceptual site model, the qualified person should consider;

• whether site and local knowledge are sufficient to support the geological and hydrogeological interpretation. For example;
  • are all contaminant sources identified?
  • have contaminant plumes been adequately delineated and characterized for the purpose of the risk assessment?
• whether sampled media and sample locations address all potential transport pathways
• whether a pathway can be considered incomplete or non-existent based on the intrinsic physical/chemical properties of the contaminant and the natural geology/ hydrology of the site
• whether a pathway can be considered incomplete based on the presence of a barrier (current and / or designed as part of the proposed land use) which relies on human intervention;
  • for the creation of the barrier and/or,
  • to communicate knowledge of the importance of the barrier on human or ecological exposure to future site owners/users as a measure to prevent future disruption or deterioration of its effectiveness
• whether all potential receptors, including sensitive receptors (for example children, pregnant woman, person with asthma), have been identified on and off the property
• whether the models to be used;
  • are suited to the conceptual site model,
  • will have adequate site data to support assumptions

The conceptual site model presented in the PSF is considered to be a preliminary model which will be confirmed, possibly modified, at the time of submission of the risk assessment.

PSF Preparation Requirements Other Attached Documents

The proponent may attach other documents which they believe support the risk assessment approach. This would include any documentation which supports deviation from best practice or regulatory requirements, if any are contemplated at the time of PSF submission, for consideration by the Director. They would also include plans for additional data collection, if any are contemplated at the time of PSF submission.

The proponent may also include in the PSF any toxicological information relating to potential adverse human health effects and surrogate ecological test species, if these have been considered at the time of submitting the PSF, on which the proponent wishes to seek ministry comment. For example, if at the time of preparing the PSF the RA team has selected surrogate species which they intend to represent the site VEC's they may provide by way of a table the VEC's selected for the site (a subset of the species present on the site) and the species selected from the literature to be used for determining the toxicity reference value (i.e., whether dog or rat toxicity data will be used to represent red fox).

If a public communication plan has been developed at the time of the PSF submission, this may be attached for the ministry comment.

If the QP_RA has not previously self declared their qualifications to the ministry, the PSF will have attached the resume, work references and post-secondary transcripts that support the QP_RA declaration. While attached to the PSF submission, the QP_RA qualifications should be bound separately from the rest of the PSF material and provided to the ministry as a single copy, so that it can easily be separated from the rest of the submission and handled in a manner which respects the privacy of the QP_RA. If a QP_RA has previously self declared, they are not required to attach supporting documentation to subsequent PSFs.

1.4.2 Public Communication

The RA property owner is encouraged to prepare a public communication plan, which includes both the general public and the local municipality when choosing the risk assessment approach. This Procedure document uses the term "public communication" to include both consultation and notification.

Notification of the RA approach to the municipality is required where the QP_RA intends to prepare an RA that assumes groundwater under the RA site does not or will not serve as a municipal water supply for a drinking water system and non-potable standards are to be developed.

The RA property owner is required to provide broader public communication in situations where the ministry District Office has indicated by way of comment on the Pre-Submission Form, that the site is located in a wider area of abatement. The property owner should also undertake public communication if there is a likelihood of contaminant migration off the RA property and in relation to any property for which risk management is being proposed. Where public communication is undertaken, a summary of any public input must be provided to the ministry.

In general, public communication is beneficial to the site redevelopment process. The proponent is encouraged to consider public communication as early as possible in the process of site assessment and redevelopment. Minimum requirements for reporting on public communication as part of the risk assessment are provided in Schedule C, Table 1 of the RSC Regulation, and are reproduced below.

If public communication is planned, the ministry recommends that whenever possible, the RA property owner include the public communication plan in the PSF. This communication plan should, as a minimum provide for:

• notification of the owners of neighbouring properties that a risk assessment will be undertaken, and
• provision for input to the risk assessment process by the local community.

Any written input offered by the community should be recorded and attached to the submitted risk assessment report as an Appendix.

The specific conditions and situation at each RA property should always be considered in determining the methods and the extent of public communication required, and the appropriate response to community input. Ideally, public concerns should be addressed throughout the risk assessment process.

The property owner should consider the goals listed below when designing and implementing a public communication plan:

• Providing an explanation of the process to be followed including the inter-relationship of the Phase one ESA, Phase two ESA, risk assessment work and remediation of the RA property, the steps to be followed at each phase, the proposed timing and the opportunities for public input;
• Providing a forum for receiving public input and information on potential contamination at the RA property;
• Providing initial and ongoing information to the public as needed, on the nature and extent of RA property contamination and the activities proposed for risk assessment and including any risk management requirements (the ministry recommends that at least 30 days notice of property activity be provided to affected stakeholders);
• Allowing public input on plans for addressing risk, including the basis for the property specific standards developed through risk assessment and ongoing management and monitoring if warranted; and
• Allowing the public to provide input on the risk associated with the parts of the proposed remedial work plan, such as soil excavation, treatment and/or transportation, which may generate dust or have impacts on other exposure pathways that may affect workers or local residents.

Examples of methods which can be considered for inclusion in a communication plan are:

• Posting a notice on the RA property;
• Advertising in the local newspapers or community bulletins;
• Delivering flyers or newsletters door to door;
• Using dedicated telephone lines to provide or receive information;
• Placing material in local libraries, community centres or establishing a temporary local office;
• Holding public meetings, information sessions or an open house;
• Establishing a public liaison committee; and/or
• Any other method of consultation or notification that, in the opinion of the QP_RA, is adequate.

Section 2. Preparation Of A Risk Assessment Report

Risk assessment (RA) reports must meet the requirements of the RSC Regulation as set out in Schedule C, O. Reg 153/04. The RA process must include both human health and ecological risk assessments in a single report. Under the RSC Regulation, the RA report now includes the following sections:

• Section 1 - Summary of Recommendations/Findings
• Section 2 - Risk Assessment Team Membership
• Section 3 - Property Information, Site Plan and Geological Interpretation
• Section 4 - Human Health Risk Assessment (HHRA)
• Section 5 - Ecological Risk Assessment (ERA)
• Section 6 - Conclusions/Recommendations
• Section 7 - Risk Management Plan (RMP) if applicable
• Section 8 - Public Communication Plan if applicable
• Appendices - including Certified Statements

The RA report must include the headings, sub-headings and minimum requirements as stated in Table 1, Schedule C of the RSC Regulation. Other headings, sub-headings or other information considered relevant may also be included in the RA report. The move towards a standard RA report format will improve consistency in RA submissions and reduce the time required for the ministry to complete reviews.

Opportunities for Report Revisions

The ministry will advise the QP_RA as early as possible in the review process if more information is needed in the review of RAs. Resubmission, or submission of additional information, may have an impact on the time required for ministry review. Provisions for making changes or additions to the RA report are set out in the RSC Regulation Section 46. At the Director’s discretion, proponents will have the opportunity to provide the requested information in an advised limited period of time or resubmit the entire report setting the timeline back to the beginning. Alternatively the proponent may choose to withdraw the submission. Failure to respond to the Director’s notice to provide the requested revision may prevent the risk assessment from being accepted by the Director.

If a risk assessment is not accepted by notice of the Director under section 168.5 of the EPA, the proponent may choose to submit a revised risk assessment or choose not to pursue the risk assessment option. If a revised risk assessment is submitted after the Director has issued a decision notice under section 168.5 of the EPA, it must be provided as a new risk assessment, starting with a new PSF, for consideration by the ministry. The basis for not accepting a risk assessment will be provided by letter in all circumstances.

General Report Requirements

In the preparation of a RA report, reference should be made to the RSC Regulation, and in particular to the following sections;

• Schedule C Part I "Mandatory Requirements"
  • Section 4 "Mandatory Requirements of Risk Assessment Reports"
  • Section 5 "Mandatory Certifications"
• Schedule C Table 1 "Mandatory Requirements For Risk Assessment Reports"

Additional requirements for those risk assessments which are subject to transition from the former Guideline for Use at Contaminated Sites in Ontario (1996) are provided in the RSC Regulation section 44 "Risk Assessment Form" and section 45 "Transition". Other unique circumstances may be subject to Schedule C section 11 "Exemption".

Guidance on the RA Report Sections "Risk Assessment Team" and "Public Communication" as specified in Schedule C Table 1 has been provided in Section 1 of this Procedure document for reference at an early stage in the risk assessment process.

General guidance on reporting the risk assessment outcome and meeting the requirements of the "Summary and Recommendations", "Conclusions and Recommendations" Report Sections of Schedule C Table 1, as well as "Appendices" as specified in Schedule C section 4, is provided in the following sections (Sections 2.1 to 2.3) of this Procedures document.

General guidance on conducting a risk assessment to support filing a RSC, including how to report on the geological setting and contaminants of concern to meet the requirements of "Property Information, Site Plan and Geological Interpretation", is provided in Section 3 of this procedure document.

Detailed guidance on conducting HHRAs and ERAs and presenting the results in accordance with the RSC Regulation are provided in Sections 4 and 5 of this Procedures document, respectively.

Additional report sections which may be required are "Risk Management Plan" and "Public Communication Plan". Guidance on preparing these sections is provided in Sections 6 and Section 1.4.2 of this Procedures document, respectively.

A control document called a Certificate of Property Use (CPU) may, at the Director’s discretion, be issued. For this reason, if a risk management plan is included in the RA report, a summary of the Risk Management Plan should be provided with the RA report to facilitate Environmental Bill of Rights (EBR) posting for public comments, as part of the approval process. The summary may be posted, as received by the ministry, as a requirement being considered by the Director.

2.1 Summary and Recommendations

As set out in the RSC Regulation, Section 1 of the RA report must provide a summary including the findings of the HHRA and ERA. This section will form the basis of information to be entered into the Brownfields Environmental Site Registry in support of filing a RSC. The information will also assist processing of the risk assessment review. Any deviations from information which was provided previously to the ministry in the PSF must be identified. Property-specific standards, risk assessment assumptions, and risk management requirements are also stated in this section. The minimum requirements for the Summary and Recommendations Section are provided in Table 1 Report Section 1 "Summary and Recommendations" of the RSC Regulation, Schedule C, and are reproduced below.

The standards specified in the risk assessment (proposed property specific standards), risk assessment assumptions and risk management measures are preferably to be listed in table form. Risk assessment assumptions should highlight key assumptions which place limits on the out come of the risk assessment, i.e. the assumptions made in the risk assessment which are critical to the acceptability of these standards (for example sensitive model parameters, risk management measures, property use assumptions).

Report Section 2 requires information on the "Risk Assessment Team". For guidance on how to complete this section please refer to Section 1.3.2 of this document.

Guidance on how to complete Report Sections 3 through 5 is provided in Sections 3 to 5 in this document.

2.2 Conclusions and Recommendations

Conduct of the risk assessment will include separate assessments for HHRA and ERA based on a single geological interpretation of the site and conceptual site model. Guidance for conducting and reporting on those assessments follow in sections 3, 4 and 5 of this procedure document. The conclusions and recommendations of the RA report must therefore summarize and consolidate the findings of the HHRA and ERA and propose the property specific standards to be used for filing a RSC. Minimum requirements for conclusions and recommendations (Section 6) of the RA report are provided in Table 1 of the RSC Regulation, Schedule C, and are reproduced below.

2.2.1 Recommend Property-Specific Soil and/or Ground Water Standards

It is not sufficient for the RA report to demonstrate that risk to human health and the environment is acceptable or negligible. Schedule C of the RSC Regulation requires that all risk assessments specify a property-specific soil and/or ground water standard (numerical value) for each COC identified in the Phase two ESA and Report Section 3 of the RA report. This is necessary because a Qualified Person (QP_ESA), when filing a RSC, is required to enter the maximum concentration of every COC at the RA property. The Brownfields Environmental Site Registry requires a standard for each COC for comparison purposes.

A recommended tabular format for summarizing the proposed property specific standards in the RA report is provided in the example below.

Special considerations may apply if the risk assessment determines that existing contaminant concentrations on the property present acceptable or negligible risk. The QP_RA can propose either the maximum site concentration (measured or estimated) as the property-specific standard, or the concentration below which adverse effects would not occur (effects-based standard), as predicted by the risk assessment. In either case the concentration proposed as the standard must be evaluated explicitly in the risk assessment and must not interfere with the proposed use of the property, as certified in the RSC.

Guidance related to excessively high property specific standards

For the purpose of clear communication to public stakeholders through the Brownfields Environmental Site Registry, the ministry expects that the proposed standard will not exceed a reasonable upper estimate of the actual concentrations remaining on the property at the time the standards are to be used to file a RSC. The ministry also expects that the proposed standard will respect public expectations regarding aesthetics (taste, odour, visibility). The ministry will not accept a concentration which is not physically possible (greater than 100% i.e. pure chemical compound) as a property specific standard. This clarity is important for fostering public and commercial confidence in the risk assessment process.

For the purpose of clarity in the risk assessment review process, it is the ministry’s preference that the standard specified in a risk assessment be no greater than an estimate (for example based on measured sample variance) of the maximum concentration existing on the property at the time of undertaking the risk assessment.

If a standard specified in a risk assessment exceeds the maximum concentration on the property by a significant amount, the property owner should be aware that the risk management measures required in conjunction with that standard may be more onerous than what is required for the actual contamination present. Risk management measures are required in conjunction with the standard, not the Phase two ESA data, and must apply to the entire property area to which the standard (and the RSC) applies. They must be sufficient to manage risk to all receptors (human and ecological) due to contamination of all portions of the property at the concentration proposed as the standard. Risk management measures may be allocated to a portion of the property only where site characterization clearly demonstrates that the rest of the property meets some other approved standard such as the applicable site condition standards published by the ministry.

Thorough site characterization therefore should be considered as a more efficient and effective approach to managing site uncertainty than the use of risk management alone.

Guidance related to the use of multiple standards at a property

If it has been demonstrated that contamination on some portion of the property does not require risk management, or requires a different risk management strategy, the property owner may choose from two alternative approaches;

• Risk management may be limited, through a CPU, to parts of the property which do not meet the site condition standards published in the document Soil, Ground Water and Sediment Standards for Use Under Part XV.1 of the Environmental Protection Act
• Some other lower concentration may be specified in the risk assessment as a separate standard, and a separate RSC filed, for the portion of the property which meets the lower concentration standard. This will require a clear delineation in the risk assessment, including a legal survey of the different RSC property areas.

Risk to all receptors (human and ecological) resulting from each concentration proposed as a standard, on and off site and in the absence of risk management, therefore must be explicitly identified in the risk assessment report in order to justify the extent of the proposed risk management measures.

A single risk assessment may propose one or more property specific standards to support filing more than one RSC. In such a case, the RSC properties should be clearly delineated in the risk assessment by way of a legally surveyed property description. The separate RSC may refer to surveyed portions of a single property or may refer to separate properties owned by one or more property owners. If more than one property owner is involved, each property must be the subject of Phase one and Phase two ESAs and the owners of all RSC properties must have signed and submitted the PSF related to the single risk assessment.

The Brownfields Environmental Site Registry can identify only one standard per land use for each RSC property description.

Guidance related to the assessment of off site risk

Under the RSC Regulation, the potential effects of a property specific standard on neighbouring off-site properties must be considered as part of the risk assessment and review process. Any expectation that a proposed property specific standard will result in an exceedance of the appropriate full depth site condition standards on a neighbouring property must be assessed and explicitly reported.

As part of the Certified Statements in the RA report Appendices, the QP_RA must certify whether meeting the property-specific standards will result in an exceedance of the appropriate full depth site condition standards at the closest off-site receptor (human or ecological). For a given COC, the ministry’s response to the potential for any off-site exceedance of the soil and/or ground water site condition standard will be determined on a case-by-case basis by the ministry District Office, which will prioritize any action that may be warranted on a specific property, considering the potential human health and ecological risk level, social and economic impacts.

Property specific standards applicable to off-site properties are not accepted by the Director under the RSC Regulation. If standards are to be proposed as a result of a risk assessment for any property, the conduct of the risk assessment should have the explicit agreement of that property owner who has signed and submitted a PSF to the Director. The RSC process does allow for a single risk assessment to be conducted on behalf of several property owners, jointly submitted by those owners to the Director and, if accepted, used for filing separate RSC based on the legal descriptions of the individual properties.

2.2.2 Special Considerations for Ground Water Standards

Mandatory risk management is no longer automatic if the ground water concentration for a given chemical parameter exceeds the 50% solubility concentration. Nevertheless, as indicated in Table 1 of the RSC Regulation, risk management measures may be required, based on a demonstration of the risk of free product formation and the need for mitigation.

Free product on a site should be removed to the extent technologically practicable. Standards specified in a risk assessment should not result in the formation of free petroleum hydrocarbon product. Standards specified for potable groundwater use should not result in a sheen, taste or odour due to petroleum hydrocarbon contamination. Consistent with the approach in place through the 1996 Guideline for Use at Contaminated Site in Ontario, the issuance of a certificate of property use and registration on title through a certificate of requirement will generally be required where risk management is necessary to control potential for free product.

If no ground water standards are proposed that exceed the 50% solubility concentration and no other special considerations apply, the QP_RA should indicate that no special considerations apply to the ground water.

2.3 Appendices

Additional documents which must be supplied as Appendices to all RA reports are identified in the RSC Regulation Schedule C;

• Section 4 "Mandatory Requirements of Risk Assessment Reports" and
• Section 5 "Mandatory Certifications"

A check list of documents to be attached to the RA report is provided below. The QP_RA is directed to the regulation regarding the required content of these documents:

• Mandatory Certifications
• Pre-Submission Form, ministry response and how ministry concerns, if any, were addressed.
• Resumes for the QP_RA and team technical leads, contact information for work references (employers, colleagues, clients) who can support experience claims of the QP_RA.
• List of documents relied upon in the preparation of the RA report.
• A summary of Phase one and Phase two ESA reports, including justification for the sampling approach, data obtained and data QA/QC evaluation.
• A copy of any reports documenting further site investigations conducted for risk assessment purposes (if applicable).
• A copy of the written notice of intention to conduct a risk assessment that assumes non-potable ground water condition addressed to the municipality in which the RA property is located, together with a copy of any response from the municipality (if non-potable ground water use was assumed).
• An engineering or hydrogeological report recommending the design of engineering and/or hydrogeological controls, including detailed plans and specifications (if applicable).

Other information may be provided as Appendices to the RA report at the discretion of the QP_RA.

Section 3. General Guidance for Conducting Risk Assessments to Support Filing a RSC

Depending on the required scope of the risk assessment, the various components set out in Schedule C of the RSC Regulation may be conducted in a qualitative or quantitative manner. However, the Ministry now requires that a property specific standard be recommended for each COC for inclusion in the Brownfields Environmental Site Registry.

Section 3 of this Procedures document describes the risk assessment procedures common to Human Health Risk Assessments (HHRA) and Ecological Risk Assessments (ERA), while Sections 4 and 5 describe procedures specific to HHRA and ERA, respectively. Section 7 describes alternative procedures that may be used for risk assessment under certain specified conditions.

3.1 Principal Elements of Risk Assessment (HHRA and ERA)

All risk assessments must include all of the following four elements for both HHRA and ERA:

• Problem Formulation/Hazard Identification/Receptor Characterization
• Exposure Assessment,
• Toxicity/Hazard Assessment for contaminants with complete exposure pathways, and
• Risk Characterization.

The elements of ERA and HHRA may be given different names. They may proceed in the sequence as listed or with many feedbacks and overlaps between the different elements.

Requirements of both HHRA and ERA are described in the RSC Regulation. Guidance for the four basic elements will be discussed in detail in subsequent sections. Depending on the objective of the risk assessment, individual elements may be conducted in a qualitative or quantitative manner.

3.2 Risk Assessment Objectives

For each of the HHRA and the ERA the QP_RA must provide a statement of the objective of the risk assessment. The risk assessment objectives determine the most appropriate procedures to follow in undertaking the risk assessment, the necessary data quality to meet the objectives and whether uncertainty in site specific property knowledge could prevent the risk assessment from meeting the objectives. For example, if the objective of the risk assessment is to demonstrate that Table 2 site condition standards are suitable for use at a particular environmentally sensitive area, uncertainty in some site specific detail may have little impact on meeting this objective provided conservative qualitative assumptions are used.

A statement of the objective of the risk assessment includes, but is not limited to, identifying the proposed use of the RA property, the receptors and exposure pathways to be assessed and choosing from the following approaches:

• conducting a quantitative risk assessment for the purpose of calculating new property specific standards, or
• conducting a qualitative risk assessment for the purpose of justifying the use of existing standard values (ministry site condition standards or standards from other jurisdictions) as property specific standards, or
• using a combination of qualitative and quantitative approaches;
• using the standard risk assessment procedures as described in Sections 4 and 5 of this Procedure document, or
• using one of the alternative risk assessment procedures according to requirements of the RSC Regulation Schedule C Part II and described in Section 7 of this Procedure document. Alternative risk assessment procedures include:
  • Limited Scope Risk Assessment,
  • Estimation of Natural Local Background Concentrations,
  • New Science Risk Assessment,
  • Wider Area of Abatement Risk Assessment.

3.3 Property Information, Site Plan and Geological Interpretation

The HHRA and ERA rely on a common description of the property, it’s geological and hydrogeological setting and contamination status. This information is normally collected and reported through Phase one and Phase two ESAs. A summary of this information which supports the approach and assumptions of the human health and ecological risk assessments must be provided with the RA report. Much of this information would have been provided with the PSF to support the preliminary conceptual site model. The information provided with the RA report would confirm or finalize the conceptual site model for use in the HHRA and ERA.

The third section of the RA report must provide a summary and analysis of information from the Phase one and Phase two ESA, including property information, a site plan and pertinent geological information. The minimum requirements for Section 3 of the RA report are provided in Table 1 Report Section 3 “Property Information, Site Plan and Geological Interpretation” of the RSC Regulation, Schedule C, and reproduced below.

3.3.1 Property Information

The property description must provide basic information on the RA property, including a summary of past and current use of the property and a summary of past and current use of all other relevant adjacent properties. The RA team should consider the general physical characteristics of the property (for example, vegetation, soil type, hydrogeology, presence and location of surface water, utility trenches, climate, geologic setting, etc.) and summarize these characteristics into a conceptual site model diagram.

3.3.2 Site Plan and Hydrogeological Interpretation of Risk Assessment Property

It is the RA team’s responsibility to utilize the results of the Phase one and Phase two ESAs, and any additional investigations required, to determine the hydrogeological setting, and the anticipated contaminant behavior in that setting and to articulate a conceptual site model of contaminant distribution for the property. Sufficient detail must be provided to demonstrate that the site has been adequately characterized and that the site and regional geology, hydrogeology and natural and contaminant geochemistry, are adequately understood to support the development of a conceptual site model and to support the risk assessment and any risk management plan proposed. The RA team must be able to provide a description of routes of potential contaminant transport in the context of property specific characteristics.

3.3.3 Subsurface Transport Component of the Conceptual Site Model

A conceptual site model is defined in the RSC Regulation in Section 3 of Schedule C as comprising specified drawings with explanatory notes (text description). The conceptual site model provides a three-dimensional (area and depth) description of site conditions that illustrates contaminant sources and distributions, release mechanisms, exposure pathways, migration routes and potential receptors. A conceptual site model must show all potential human receptors and valued ecosystem components (VEC) and exposure pathways specific to the site and adjacent properties. Each relevant pathway is to be provided, including those that may be eliminated through risk management measures. The conceptual site model is expected to highlight the effects of any existing or anticipated pathway barrier on potential exposure pathways. Therefore the conceptual site model must distinguish between the routes of exposure which would potentially exist without risk management measures and routes which are expected to exist under conditions which include risk management measures (existing or future pathway barriers).

The conceptual site model for sub-surface transport provides an organized, three dimensional picture of the hydrogeologic setting (minimum of site plan and cross section). A narrative should be provided to explain the groundwater flow and contaminant behavior, interactions with receptors, as well as consideration of the consequences of natural and human activities.

The conceptual site model must meet all the requirements specified in Schedule C Section 3 and described in section 1.4.1 of this Procedures document for the PSF. The conceptual site model presented in the RA report should be a finalized and refined version of the model presented in the PSF. Any changes to the conceptual site model which may impact the risk assessment outcome must be identified in Report Section 1 "Summary of Recommendations/Findings" under the heading "Deviations from Pre-Submission Form".

3.3.4 Contaminants of Concern

It is intended that the QP_RA and the QP_ESA work together to identify COCs which require the development of property specific standards.

The selection of chemicals as COC must include all contaminants exceeding site condition standards with reference to the RSC Regulation Part IX "Site Condition Standards and Risk Assessment". In addition, the QP_RA and the QP_ESA should consider if the following apply;

• Are there any characteristics of the property which may increase the likelihood for one or more contaminants to interfere with the property use beyond that considered in the development of the ministry site condition standards?
• Are there any contaminants on the property which may degrade to a more toxic product?
• Are there any chemicals measured at the property which do not have site condtions standards published by the ministry?
• If there are chemicals without ministry site condition standards, are they likely to interfere with property use?

Based on consultation with the QP_ESA, COCs may include one or more contaminants which meet the site condition standards if there is some concern on the part of either QP that they may interfere with the proposed use of the property. The latter may occur if the conceptual site model on which development of the site condition standards was based did not include site specific features which may increase the level of risk to the proposed receptors (for example contaminated groundwater situated within 1 m distance from a building slab). The conceptual site model on which development of the site condition standards was based is described in the document "Rationale for the Development and Application of Generic Soil, Ground Water and Sediment Criteria for use at Contaminated Sites in Ontario" (MOE 1996) as updated from time to time.

Also, based on consultation with the QP_ESA, COCs may include contaminant degradation products or other chemicals for which there are no published site condition standards and for which there is some concern on the part of either QP that they may interfere with the proposed use of the property.

If a chemical has been measured at the property which does not have a ministry site condition standard, the QP_ESA must decide if the chemical is a COC based on an understanding of geoscience. For example, natural elements of the earth’s crust (such as Al, Fe, Ca) may be measured but have no ministry site condition standards. These chemicals are generally ubiquitous in soil at non-toxic concentrations but may become limiting to site use at some concentration. The QP_ESA must determine within the context of the Phase two ESA if the presence of a chemical without a standard is trivial or if there is potential for concern. If the chemical is of potential concern, the chemical should be evaluated as part of the RA and a property specific standard should be developed. The QP should refer to the following sections in the RSC Regulation for making this determination:

• Part IX section 43(3)
• Schedule A certifications required in the RSC, including but not limited to
  • Section 6,
  • Section 10(3), or
  • Section 16(2) and 17(3).

Where a chemical is measured and there is no site condition standard, the QP_RA has the following options; 1) submit a new science RA (refer to section 9 of Schedule C on the RSC Regulation and Section 7.3.1 of this document) to propose a property specific standard or 2) to identify in the summary of site investigations in the RA report that, in the opinion of the QP_RA and the QP_ESA, a risk assessment is not required for this contaminant. The certifications made by the QP_ESA in the RSC will confirm that there is no evidence of contaminants left on the property that will interfere with the proposed use of the site.

The QP_RA must provide in the RA report a brief description of the sampling program, a description of the COCs and justification for determining if contaminants measured on site are not considered COCs. The QP_RA should consider the following in identifying COCs:

• Contaminants identified on the property that exceed the applicable site condition standards. At the discretion of the QP_ESA, COCs should include chemical parameter(s) for which there is no site condition standard specified in the Soil, Ground Water and Sediment Standards document with reference to Part IX section 43 of the RSC Regulation;
• The hazard profile (see guidance on Toxicity Assessment, Sections 4 and 5 of this Procedure document) of each identified COC and potential degradation products, including but not limited to, adverse effects, environmental fate and transport, persistence and bioaccumulation (for example vinyl chloride can be generated from TCE under anaerobic conditions);
• Uncertainty that exists in terms of the completeness of the Phase one ESA and/or Phase two ESA and the quality of data to be relied upon in the risk assessment. A contaminant should be considered a potential COC if the QP_RA is not confident that the data demonstrates that a pathway is incomplete or that a ministry site condition standard is not exceeded.

Some or all of these COCs may require a detailed quantitative risk assessment in order to justify a property specific standard. Others may be evaluated using a qualitative descriptive approach (non-numeric) or a qualitative screening (numeric) approach.

A risk assessment is not required for contaminants that are not detected or present at concentrations less than the detection limits identified in Analytical Methods Used in the Assessment of Properties Under Part XV.1 of the EPA.

3.3.4.1 Screening Process for Quantitative Risk Assessment

For certain properties the list of COCs which potentially require a quantitative assessment may be lengthy. The QP_RA may wish to reduce the number of COCs to be carried through the quantitative calculation of risk. An acceptable technique for assessing contaminants for detailed quantitative risk assessment is to conduct a screening assessment on the contaminants at the property. A screening assessment is a preliminary tool with specific purposes as follows:

• To identify if, in the opinion of the QP_RA, there is an insignificant likelihood of risk to human health or the natural environment; and/or
• To assist in determining the scope of the risk assessment.

For the purposes listed above, a screening assessment may be undertaken as part of the problem formulation step and may be presented with the PSF. The results of this process are qualitative or semi-quantitative only and can be used only in contaminant selection, eliminating irrelevant routes and/or pathways of exposure or irrelevant receptors for further consideration in the risk assessment and in justifying standards developed through some other process . The result of any screening assessment must be reported as a qualitative risk assessment in the risk assessment report.

The main principle in screening or short-listing COCs is that all potential COCs without site condition standards should be included for detailed assessment (together with all contaminants exceeding the applicable site condition standards) unless there is information that supports exclusion. The following principles are to be used as guidance when considering a screening approach.

If a screening process is employed the following should be provided:

• The complete list of COCs found on the RA property, including a summary of the monitoring data and detection limit for each COC and illustration of the spatial distribution of COCs on the property,
• The process for screening which COCs are to be followed through quantitative calculations in further steps in the risk assessment process; specifically, toxicity/hazard assessment and exposure assessment, and
• An appropriate property specific standard recommended for all COCs found on the property, including those deemed to present no significant risk through a screening process. The recommended property specific standard must be determined from some means other than the screening method (see section 2.2.1 and sections 4 and 5 of this procedure document).

When considering information to support exclusion, it should be noted that COCs lacking site condition standards should be included for quantitative assessment when these COCs are:

• Known or probable carcinogens;
• Contaminants for which no human threshold has been established by a credible agency (see Section 4.3.2 of this Procedure document);
• Contaminants which are present at toxic concentrations and don't degrade or metabolize; and/or
• Contaminants which degrade to other contaminants which may then be present at toxic concentrations.

Screening assessment is a type of qualitative risk assessment. The screening process uses risk assessment techniques, however, screening assessments are usually based on a 'worst case scenario' instead of verifiable property specific conditions. For example, the screening assessment could use maximum concentrations in each exposure pathway and maximum exposure periods and the physical/chemical characteristics of the most toxic isomer or member of a chemical group. A screening assessment should contain the same elements as a quantitative risk assessment: i.e., 1) Problem Formulation, 2) Exposure Assessment, 3) Toxicity Assessment and 4) Risk Characterization. However, screening assessments cannot provide a quantitative estimate of risk or back-calculate a property specific standard.

A screening assessment may include a consideration of criteria from another reputable jurisdiction, together with an assessment of the basis of that criterion, as part of the screening process. Maximum concentrations found on site can also be proposed as property specific standards, as described in Section 2.2.1 of this procedure document, for COC which pose negligible risk based on a screening assessment.

A comparison of the types of standards which may be supported by a screening assessment with those which may be supported by the quantitative approach and the non-numeric qualitative approach are summarized in the table below. The suitability of a particular approach for a particular circumstance must be explained in the risk assessment. The ministry will consider whether a particular approach is suitable as part of the risk assessment review.

3.3.4.2 Summary of Sampling Program

All risk assessments are dependent on the quality of information provided through the property characterization, carried out in the Phase one and Phase two ESAs and any other investigations, and the associated uncertainty in the supporting toxicological and exposure information. At a minimum, Phase one and two ESAs must be conducted in accordance with CSA standards as modified by the RSC Regulation. Other studies relating to sediments, surface water and biota may also be required to support a risk assessment. These should be conducted with consideration of the most recent ministry guidance and best scientific practice.

The RA report must include a summary of the Phase one and two sampling programs, specifically considering data quality, uncertainty and suitability of the data for use in the RA, and details of any additional sampling undertaken to support the RA. On a case by case basis the ministry may request additional information or copies of Phase one or two ESAs and/or other relevant site reports that the ministry deems necessary for review. Characterization of the RA property and COCs in the RA report should fully document the following:

• what investigation methods were used;
• what portions of the property or environmental media remain uncharacterized, if any;
• how the risk assessment objective can be addressed through the use of available information;
• the quality assurance/quality control procedures used; and
• an analysis of the sources, relative magnitude and implications of uncertainty in the data obtained.

3.3.4.3 Data Quality Assessment

Quality assurance and control is necessary in both sample collection and sample analysis to ensure that the data utilized in a risk assessment is representative of the site conditions on a RA property. The collection and analyses of environmental data in Phase two ESAs should be carried out in accordance with the CSA Phase II ESA Standard (CAN/CSA Z769-00) as modified by the RSC Regulation. The data quality objectives which the site assessment information should meet are specific to the issues addressed by the risk assessment and are to be determined by the QP_RA as part of the risk assessment.

The RSC Regulation requires that the QP_RA demonstrate that the data used for the HHRA and ERA is sufficient to meet the objectives of the assessments. In the RA report the RA Team should discuss the completeness of all data sets and indicate whether appropriate analytical methods were utilized (for example, the methods comply with Section 47 "Analytical Procedures" of the RSC Regulation and the method detection limits were met).

The RA Team is expected to use standard data quality measures of representatively and reproducibility (accuracy and precision) when evaluating the data. The RA team should consult the sampling guidance portions (section 5 through 7 and section 9) of the former guidance document "Guidance on Sampling and Analytical Methods for use at Contaminated Sites in Ontario" (MOE 1996) and any replacement guidance as updated from time to time.

The required QA/QC data quality objectives will be dependent on the sensitivity of the risk assessment outcome to uncertainty in the data. The QP_RA and QP_ESA should exercise professional judgment in selection of appropriate techniques to obtain representative samples and achieve the risk assessment objective. The designer of the sampling program should have expertise in the design of sampling for the subject environmental medium.

It should be noted that it is the responsibility of the QP_RA to ensure that all analytical results used to support critical assumptions in the risk assessment must comply with Section 47 "Analytical Procedures" of the RSC Regulation. In addition, the QP_RA should always be diligent about the quality of analytical results obtained from a laboratory. If historical investigations on a risk assessment property included analysis of samples which may be questionable the QP_RA should clearly identify these analyses in the risk assessment and provide the ministry with confirmatory analysis and assurances that the questionable samples have not been relied upon in any way in the risk assessment.

3.3.4.4 Site Investigation and Currency of Property Data

Property characterization data used in the assessment should reflect the most recent site conditions. This is to assist the QP_RA in ensuring that certified statements in the risk assessment report relate to site conditions which are still relevant at the time of signing the report.

Substantial time may elapse between an initial Phase two ESA, the initiation of the risk assessment and the submission of a RA report. The RA Team should satisfy themselves that contaminants of concern concentrations on the site and the problem formulation/hazard assessment used in the risk assessment represent site conditions at the time the risk assessment report is completed and signed.

Information contained in the RA report, including the description of site conditions, COCs and ecotoxicity tests, should include measurements carried out within the two years prior to submission. Two years is proposed based on a typical period which may elapse between initiating a site assessment and submitting a risk assessment report. If the Phase two investigation was conducted earlier than two years from RA submission, the QP_RA should assess the data and confirm with more recent sampling any information which may have changed, potentially impacting the risk assessment outcome. The use of older data is ultimately left up to the judgment of the QPs, as two years may be sufficient or insufficient, depending on the contaminant, receptors and site circumstances.

Additional characterization may be undertaken, such as collection of additional property or receptor characterization data, to reduce uncertainty in the overall risk assessment so that the RA results will be useful for making meaningful risk management decisions.

Section 4. Requirements Specific to Human Health Risk Assessment (HHRA)

4.1 Problem Formulation Component of HHRA

The first component in the HHRA is Problem Formulation. The minimum requirements for the Problem Formulation component of HHRA are provided in Table 1 of the RSC Regulation, Schedule C and are reproduced below.

4.1.1 Human Health Conceptual Site Model

The human health conceptual site model is a physical description of the potential contamination problem to be assessed from a human exposure and health risk perspective. The human health conceptual site model must meet the requirements of the RSC Regulation as described in Schedule C Section 3(8)(b) and Table 1 Report Section 4 "Human Health Risk Assessment". Potential receptor populations for the proposed property use must be identified along with all associated potential exposure routes and pathways. For each of the sources of COCs for the RA property, the QP_RA must ensure that the conceptual site model identifies 1) the release mechanisms and transport pathways, 2) all human receptors located both on and off the RA property, as well as exposure points and routes of exposure.

The human health conceptual site model must identify potential exposure pathways for those receptors based on physical/chemical characteristics of the COCs and geological characteristics of the site as identified in the subsurface transport component of the conceptual site model in Report Section 3.

The human health conceptual site model must clearly distinguish between pathways which are naturally incomplete and those which may be rendered incomplete through risk management measures.

For each applicable receptor, the RA team should identify all potential on-site and off-site exposure pathways (for example soil ingestion) based on the characteristics and anticipated activities of that receptor and the expected mobility of the potential COCs under the geological conditions present at the site. For each receptor and exposure pathway, the RA team should indicate further if a man-made barrier or measure to interrupt this pathway is present or anticipated.

Any exposure pathways which can be anticipated based on chemical properties and site geology should be included in the risk assessment. Elimination of these pathways from assessment will require justification in the form of pathway-specific site assessment evidence. Pathways which can be anticipated but which will be mitigated by a barrier or other measure should be included for the assessment of risk level. The barrier or other measure must be identified as risk management measures in the development of property-specific criteria.

4.1.2 Risk Assessment Objectives

The QP_RA must provide risk assessment objectives which describe the approach to studying the potential contamination problem (refer to Section 3.2 of this Procedure document) with reference to the human health conceptual site model (Section 4.1.1) and demonstrate that data used in the HHRA are sufficient to meet those objectives. It is important to state whether the RA is a qualitative or quantitative assessment of risk and the type of approach used for the human health risk assessment.

Examples of HHRA Objective Statements would be;

• Example 1:

  "The objective of this HHRA is to provide a qualitative demonstration that the Table 2 site condition standards are appropriate to protect human health at this site using a modified generic approach. A risk assessment is required because the site is located in an Environmentally Sensitive Area according to Section 41 of Ontario Regulation 153/04 due to the proximity of a surface water body. The HHRA will demonstrate the acceptability of the generic conceptual site model as described in the Rationale for the Development and Application of Generic Soil, Ground Water and Sediment Criteria for use at Contaminated Sites in Ontario (MOE 1996) for human receptors, and will justify modification of the generic standard for human receptors based on a limited set of applicable exposure pathways. The proposed land use is high rise residential. Component values for the vapour intrusion pathway into indoor air and exposure to adult and child residents and maintenance workers will be evaluated in the HHRA. Direct contact and ingestion pathways will be justified as incomplete."

• Example 2:

  "The objective of the HHRA is to provide a quantitative evaluation of risk of 1,3,5-trinitro-1,3,5-triazine (RDX), a chemical for which there are no site condition standards, and to propose a human health risk-based Property Specific Standard using a New Science risk assessment approach. The proposed property use is for single family residential. The HHRA will evaluate dermal contact with soil, soil ingestion and inhalation pathways and exposure to adult and child residents and maintenance workers. Ground water use on the site is non-potable. The vapour migration pathways will be demonstrated as incomplete."

4.1.3 Discussion of Data Quality

As indicated in the table above, the RSC Regulation requires that the QP_RA demonstrate that the data used for the HHRA and described in Section 3 of the RA report is sufficient to meet the objectives of the assessment. Data quality or availability may be insufficient for a quantitative assessment, for example, and a qualitative approach may be proposed. Examples of data quality problems which may impact on the risk assessment approach include;

• Detection limits above the site condition standard value (selection of COC),
• Low analytical recovery,
• High relative standard deviation,
• Variable monitoring data, inconsistent year-to-year trend,
• Assumption for one or more pathway relies on old data, data based on analytical method that does not comply with section 47 of the RSC Regulation, insufficient monitoring or no supporting data.

Uncertainty in the data resulting from variable or poor data quality, as well as any data gaps should be discussed in terms of the RA approach used to accommodate them. The QP_RA should explicitly discuss the extent to which suspect data can and will be relied upon in the RA.

4.2 Exposure Assessment

Exposure assessment is a detailed analysis of the potential contamination problem as described in the human health conceptual site model (section 4.1.1 of this procedures document). Exposure assessment is the determination or estimation of the magnitude, frequency, duration and routes/pathways of exposure for the COC, and assessment of the uncertainties associated with the determination. Qualitative or quantitative exposure assessment may be undertaken according to the RA objectives as described in sections 3.2 and 4.1.2 of this procedures document.

The HHRA exposure assessment should describe:

• All relevant on-site and off-site human receptors that could be affected by contamination
• Receptor characteristics that are clearly articulated in the RA report, and
• Potential exposure routes and pathways.

Minimum requirements for the Exposure Assessment component of the HHRA are provided in Table 1, Schedule C of the RSC Regulation and are reproduced below.

Additional guidance is provided in the following sections of this procedures document.

4.2.1 Receptor Characteristics

The RA report should describe the characteristics of all relevant on-site and off-site receptors identified in the human health conceptual site model as being potentially exposed to COCs. Receptor characteristics should be defined to include gender, age (including elderly), predisposing physiological and/or medical conditions (for example, asthmatics, immunologically impaired, pregnant women, etc.) and exposure variables (for example, breathing rate, water intake, soil dermal contact, etc.).

In the event that the future property use has not been predetermined for a particular property, it should be assumed for the purpose of exposure modelling that the property will be residential in nature. Any departure from this assumption will require justification.

The QP_RA should identify receptor populations currently present at or near the RA property and those that may be present in the proposed use of the property considering the following;

• The proposed use of the RA property, distance to the closest receptor, public accessibility and receptor activities and patterns, including but not limited to the proportion of time the potentially exposed populations spend in the area; the proportion of time human activities occur primarily indoors or outdoors; variation due to seasonal changes; any property-specific population characteristics that might influence exposure;
• Use of the ground water for drinking or agricultural purposes under present and future conditions;
• The receptor sub-populations of potential concern: any group with increased sensitivity, (for example, infants, asthmatics, elderly) either due to, for example, the behaviour, activity pattern or health status of the sub-population or to the inherent toxicity of the COC including, but not limited to, schools, day care centres, hospitals, retirement communities, nearby residential areas with children, and hunters/gatherers at or near the property;
• Uncertainty that exists in terms of characterization of complete exposure pathways and potential receptors (extent and quality of supporting site data, understanding of proposed land use and knowledge of uses and likely uses of adjacent or potentially impacted sites).

Receptors should include those who may be exposed during the proposed property use, as well as during remediation activities, while giving consideration to the property surroundings. This also includes consideration of occasional receptors, including but not limited to visitors and utility workers. Each receptor should be considered to the level of detail appropriate to meet the objectives of the HHRA (refer to Section 4.1.2 of this procedure document).

4.2.2 Pathway Analysis

In the RA report the pathway analysis must identify the exposure routes and pathways considered potentially complete or complete without risk management measures. Any exposure pathways which can be anticipated based on chemical properties and site geology should be included in the exposure assessment. Elimination of these pathways from assessment will require justification in the form of pathway-specific site assessment evidence. Pathways which can be anticipated but which will be mitigated by a barrier or other measure should be included for the assessment of risk level. The barrier or other measure must be identified as risk management measures in the development of property-specific criteria. The analysis should address the exposure pathways of concern, including exposures via all potential media, and considering the current and/or future condition of the RA property without risk mitigation measures, including the following:

• Exposure pathways of concern according to the human health conceptual site model (Section 4.1.1 of this procedure document);
• The sources for all potential releases (past, present and future);
• The potential receiving media (air, surface water, ground water, soil, sediment, biota);
• Evaluation of the physical and chemical fate and transport properties of the COC to identify the media that are receiving or may receive the property-related contaminant;
• The exposure points (i.e., where the potentially exposed population can contact the COC); and
• The exposure routes (could include but not limited to ingestion of soil/water and/or garden produce, inhalation of vapour, inhalation of soil particles and dust, dermal contact with soil/water and other routes that may be associated with the contaminated media).

The following points should be considered when evaluating exposure pathways.

• Discuss the environmental fate of the contaminants including possible degradation. When sufficient laboratory and field evidence indicates that a contaminant could be degraded/biodegraded (transformed/biotransformed) to a relatively more toxic and persistent intermediate/product, the future concentration of the potential degradation product/intermediate should be estimated from the present concentration of its precursors, if possible (for example, the anaerobic biodegradation of chlorinated aliphatics in ground water).
• Identify direct and indirect routes (via intermediate receptors such as garden produce) and pathways of exposure for each receptor.
• Taking into account the proposed property use, plans for construction and the fate and transport of the contaminant in the environment, identify and document relevant exposure scenarios and exposure route/pathways to on-site and off-site human receptors.
• Justify the exclusion (if any) of receptors and exposure route/pathways associated with development of the component values for the full depth generic site condition standards (Rationale for the Development and Application of Generic Soil, Ground Water and Sediment Criteria for use at Contaminated Sites in Ontario, 1996 MOE).

4.2.3 Exposure Estimates

In some cases a qualitative approach may be taken to exposure estimation by using highly conservative (screening level) exposure estimates or estimates based on the ministry generic exposure scenario (Rationale for the Development and Application of Generic Soil, Ground Water and Sediment Criteria for use at Contaminated Sites in Ontario, 1996 MOE) rather than developing site specific exposure estimates. The qualitative assessment of risk must provide a descriptive justification for the use of information not specific to the site. The justification should indicate why site specific information was not measured or not quantifiable for the purpose of the risk assessment and why the substitute information is appropriate. This approach would be suitable if it meets the risk assessment objectives identified in Report Section 4 of the RA report.

In most cases, quantification of exposure estimates will be required to meet the risk assessment objectives. Quantification of the exposure to the receptors refers to the calculation of intake or uptake rates or delivered target dose for each exposure pathway/route and the total aggregate exposure if relevant. Quantification of the contaminant intake and uptake should be done for each potentially complete exposure pathway. Quantification should include the following information:

• Exposure concentration (arithmetic average of and range or distribution of concentration that is contacted over the exposure period) at the external exposure point for each pathway,
• Contact rate (amount of contaminated medium contacted per unit time or event) and/or absorption rate, and
• Total time of exposure (estimated from exposure frequency and duration).

Reasonable maximum as well as average estimates of exposure or distribution for relevant populations should be developed based on both current and future property use assumptions, and measured concentrations on the property.

Fate and transport models are frequently used to predict the likely current extent of contamination as well as to assess the behaviour of contaminants under potential future scenarios. Such modeling can be useful to direct sampling programs and draw conclusions regarding off site migration of contaminants. When a fate/transport model is utilized in the RA to predict contaminant concentrations in soil or ground water, the predicted concentrations should be verified through field sampling wherever possible. For modelling that predicts indoor air concentrations, field sampling of both soil gas at basement depth and indoor air may be warranted.

In some cases, quantification may also include exposure from other sources/pathways/routes not specifically associated with the RA property, such as food ingestion, water supply and ambient air (i.e., typical background exposures) if sufficient information is available.

In conducting quantitative exposure assessment the following should be considered;

• Document the exposure models, model assumptions and characteristics of the receptors used for evaluation of exposures.
• Provide general equations and sample calculations for evaluating human exposure for the various pathways.
• Calculate exposures to the different receptors from various pathways identified for different contaminants.
• A contaminant source, for the purpose of a HHRA is an environmental media including but not limited to soil, ground water, air and garden produce.
• In the calculation of uptake the COC concentrations should be characterized with an estimate of the average and the upper range of the data, for example using the mean and maximum or 95^th percentile. The US EPA's Superfund program has traditionally used a 1-sided 95^th UCL for the mean as the concentration term in point estimates of reasonable maximum exposure for human health risk assessment (US EPA, 1992; 1997). It is recommended that the RA Team consider the US EPA's Risk Assessment Guidance for Superfund (RAGS) as a starting point for the most appropriate estimate of reasonable maximum exposure (RME), and to consider other options that are available. It should be noted that any methods chosen for use in the development of an exposure point concentration will be driven by the quality and quantity of data available.
• For many contaminants, especially carcinogens, if experimental animal data are used to establish a dose response relationship for a chronic effect in humans, the contaminant is usually administered to the animals starting when they are very young through their normal lifespan. Given the same concentration in a given medium, the dose per body weight for infants, children and adults can vary considerably. Furthermore, the dose of contaminants can vary during the course of a person’s lifetime due to the various life stages. To allow for comparison on the same basis, the RA Team should calculate the weighted average chronic daily intake (CDI) as described in Appendix B of this Procedure document.
• Consideration of background exposures other than exposure to on-site contamination (soil, air, water, etc.), if included, should also be discussed with reference to the property specific exposure.
• Analysis of the major sources of uncertainty and how they affect (quantitatively, if possible) the exposure estimates. Uncertainty in the pathway analysis, for example, should be discussed in terms of the dependency of the exposure estimates on pathway assumptions that are unconfirmed or beyond the knowledge and control of the proponent.

If computer models are utilized, ensure the models have been validated and/or are considered acceptable based on scientific principles. These models should also be available in the public domain. Use of proprietary models may be considered only when sufficient documentation of the modelling is provided. Use of proprietary models will require additional ministry review as provided by the RSC Regulation (refer to Schedule C, section 9 of the RSC Regulation). Such models (validated and/or accepted) should be accompanied by available technical support documentation of basic principles, user instructions, etc. The documentation should include all mathematical expressions and assumptions used in the model(s).

If proprietary models and any supporting documentation are considered confidential, such material should be clearly marked confidential. In either case, review of a RA report will be facilitated by provision of any computer software being utilized for the exposure calculations. The ministry will require evidence that such software models are provided in a manner that will not infringe any third person’s copyright. The rationale for the suitability of any chosen model to the problems posed by a property should also be documented (refer to Section 7.3.2 of this procedure document).

When conducting probabilistic modelling, statistical distributions developed from site-specific data or obtained from published peer reviewed scientific literature applicable to the site in question should be used for parameters associated with receptor characteristics (refer to Section 7.3.3 of this procedure document). The statistical distributions used in probabilistic modeling may require additional time for ministry review, as provided by the regulation (refer to Schedule C, section 9 of the RSC Regulation).

4.3 Toxicity Assessment

Toxicity assessment is the determination of the quantitative relationship between the magnitude of exposure and the probability of occurrence of a particular adverse effect, as well as the uncertainties associated with the determination. Toxicity assessment is required for all COCs for which there are potential or completed exposure pathways as determined through the process described in Section 4.2.

Minimum requirements for the Toxicity Assessment component of the HHRA are provided in Table 1, Schedule C of the RSC Regulation and are reproduced below.

Additional guidance is provided in the following sections of this procedures document.

4.3.1 Hazard Assessment

Hazard assessment must document the potential adverse effects to human health and the environment which are associated with COC exposure. Toxicological information must be provided that is being considered to evaluate potential human health effects for each of the COCs including information on toxicological end points (i.e. developmental/ reproductive) and time scale of effects (i.e. acute/chronic) , which are considered relevant for the pathways and receptors identified in Report Section 4 under Exposure Assessment.

4.3.2 Dose Response Assessment

Dose response assessment must identify appropriate toxicity values by providing:

• A description of the relationship between the magnitude of exposure for different routes and the occurrence of adverse effects for the receptors, and
• An analysis of the major sources of uncertainty on both hazard assessment and dose response assessment, and how such uncertainty affects the outcome of the toxicity assessment. The combined use of uncertainty factors and bioavailability factors, for example, may result in a highly conservative estimate, or less conservative estimate, of the toxicity reference value (TRV).

Ministry toxicity values published in the Rationale for the Development and Application of Generic Soil, Ground Water and Sediment Criteria for use at Contaminated Sites in Ontario (1996 MOE) should be used in preference to TRV from other jurisdictions unless there are TRV published more recently by a credible regulatory agency listed below. A search of the most recent TRV data published by credible agencies should have been conducted within two years prior to submission of the RA report. For those contaminants for which the ministry has not developed any toxicity values, TRV published by credible regulatory agencies may be used.

Credible agencies are those which incorporate the following in developing TRVs:

• A rigorous peer review mechanism by credible experts/multiple regulatory bodies/jurisdictions and/or academia,
• Ongoing review and updating of values on the basis of new studies or advances in science, and,
• Published and/or publicly available TRV values, together with the basis for the value selection.

Examples of credible regulatory agencies include but are not limited to US EPA (IRIS, HEAST databases), California EPA, World Health Organization (WHO) and Health Canada. Toxicity values published by these agencies are generally considered acceptable to the ministry with limited review. For contaminants with no ministry standard, the use of TRV from agencies other than those listed above will require additional time for ministry review as provided by the regulation (refer to Schedule C, section 9 of the RSC Regulation). The ministry will notify the QP_RA as soon as practical if any toxicity values proposed for use in a new science risk assessment will require the 22 week review timeline.

If data from a credible agency is used, it should be accompanied by:

• A discussion of the rationale used by the agency in the choice of the critical and supporting information study to develop their TRV,
• A description of how the considerations of the agency (dose-response model, uncertainty factors, etc.) are applicable to the receptors and conditions of the property in question, and
• Documentation of the description and evaluation of the toxicity assessment and provision of a rationale for adopting the particular toxicity assessment over others that were assessed.

It may not be possible or appropriate to conduct quantitative calculations for risk assessments where there is insufficient data or no pre-existing toxicological assessment of the contaminant. In general, when a contaminant has not been assessed and an exposure limit, TRV or dose response relationship has not been established by regulatory credible agencies, quantitative calculations for risk assessment should not be undertaken without prior consultation with the ministry. Analysis of published toxicity data other than described above by a credible agency is highly discouraged and will generally not be accepted by the Director. In the exceptional case where no TRVs are available for a contaminant but sufficient and defensible scientific information is available in the published literature and/or public domain, a proponent may be allowed to develop a TRV after consultation with ministry toxicologists.

A lack of relevant data should lead to the following conclusions:

• The present status of scientific knowledge does not allow the quantitative evaluation of human health risk, and
• No property specific human health-based standard can be established.

Recommendations can be made that, for the protection of human health and in the absence of adequate knowledge of human health risk, exposure to humans be reduced as much as possible and property-specific site condition standards be based on other factors (for example the full depth background site condition standards in Table 1 of the Soil, Ground Water and Sediment Standards). When no site condition standard exists for a given chemical parameter, the property owner may choose to adopt a background-based or effects-based soil or groundwater value from another credible regulatory agency. Under the RSC Regulation, adopting a standard or guideline for environmental media (soil, water, air, sediment, garden produce) from another jurisdiction, if no ministry site condition standard exists, may be considered a new science risk assessment (refer to Schedule C, section 9 of the RSC Regulation).

The toxicity reference value TRV selected for use (i.e. RfD, RfC, cancer slope factor or unit risk factor, TDI) should be:

• based upon the most recent and defensible values from credible agencies (for example U.S. EPA IRIS database, WHO, or Health Canada),
• be compatible with the nature of receptors, exposure regimen and duration, and routes of exposure, and
• identified for the correct chemical entity (for example isomer, oxidation state, speciation, chemical form of the contaminant) as identified on-site, for the relevant routes of exposure.

Caution should be exercised in converting toxicity data as follows:

• converting the TRVs from one route of exposure to another must be supported with adequate rationale depending on the availability of route-specific studies, or scientific evidence indicating route-independence of toxic end-points;
• converting toxic effects from short-term exposure to toxic effects expected from long-term or chronic exposure must be supported with TRVs from appropriate studies. Such an approach must clearly indicate that the toxicity endpoints of long-term and short-term exposure are consistent and mediated by the same mechanisms;
• using Occupational Exposure Limits (OELs) for site-specific risk assessment purposes may not be an appropriate rationale. In general, OELs apply strictly to workers under specific exposure patterns deemed to be appropriate in the labour regulation.

4.4 Risk Characterization

Risk characterization must include evaluation of the contribution from the different exposure routes and media to the overall risk. In the characterization of risk, the QP_RA should describe the following:

• the nature and magnitude of the risk from each route of exposure, and from all routes combined if relevant and supported by the toxicity profile of COCs;
• whether current or future levels at or near the property are of potential concern to receptors, on and off the property;
• the populations and sub-populations at greatest risk; and
• the uncertainties associated with the overall analysis.

Minimum requirements for the Risk Characterization component of the HHRA are provided in Table 1, Schedule C of the RSC Regulation and are reproduced below.

Additional guidance is provided in the following sections of this procedures document.

The QP_RA should provide clear, unambiguous statements regarding potential health risks. This means providing a complete qualitative description and interpretation of the risks to biological systems based on the available site-specific data and not just a numerical listing of the risks. The Risk Characterization element should include, but may not be limited to the items discussed in the following sections.

Human health risk characterization should account for the following:

• When a compound is known to degrade/biodegrade in the environment to a relatively more toxic and persistent intermediate or by-product, any significant human health risk due to the biodegradation intermediate or by-product should be characterized (for example, trichloroethylene to vinyl chloride).
• The exposure to the contaminant on-site should be compared, if possible, to the exposure limits (TRV) of the same chemical entity (for example isomer, oxidation state, speciation chemical form of the contaminant), corresponding to the same route of exposure.
• The human receptor(s) or sub-group(s) evaluated should correspond to the human population for which the TRV are developed.
• Intake rates should be compared to TRVs that are based on administered doses and uptake rates should be compared to TRVs based on doses absorbed systemically. If there are no demonstrable differences in uptake between the media used in the toxicity study and the media for the relevant pathway addressed in the risk assessment, adjustment to reference doses for bioavailability should not be made.
• If a QP_RA chooses a probabilistic approach, in general, the resulting 95^th percentile of the exposure term is recommended for characterizing the RME risk, while both the arithmetic mean and median (50^th percentile) should be used to characterize the central tendency of the data. The QP_RA should provide supporting information, including the statistical distribution and accompanying rationale for all input variables, correlation between relevant input variables, the statistical sampling method and number of iterations and sensitivity analysis.
• If risk-based TRVs are recommended for non-threshold effects, such as for some carcinogens, which require the implementation of a risk management plan, soil concentrations corresponding to various risk levels (10⁻⁴, 10⁻⁵, 10⁻⁶, etc.) should be listed.
• In the case of chemical mixtures inducing similar effects in the same target organs/tissues (for example, similar types of liver tumors) and/or acting through similar mechanisms or modes of action, the QP_RA should consider estimating the combined risk or hazard index for the mixture. A detailed discussion should accompany and support the proposed methodological approach.
• If the RA property owner chooses to include evaluation of alternative remedial action plans for their effectiveness in reducing human health risk, each modification to the exposure scenario and calculations should be presented along with the baseline exposure estimates.

If a quantitative analysis of toxicity and/or exposure assessment has been undertaken, contaminant-specific toxicity information must be compared against measured contaminant exposure levels and levels predicted through fate and transport modelling from which risk values can be derived.

If a quantitative analysis of toxicity and/or exposure assessment was not undertaken, the justification for not providing a quantitative analysis must be provided and a qualitative characterization of risk must be provided.

4.4.1 Quantitative Interpretation of Health Risks

When a quantitative assessment of health risk is the objective of the HHRA, the minimum requirements, as specified in the RSC Regulation Schedule C Table 1 (reproduced below), are to be included in the RA report.

A comparison of the TRV identified through toxicity assessment (as described in section 4.3) with the dose calculated through exposure assessment (section 4.2 of this procedure document) provides a 'forward driven' science-based calculation of risk. The regulation requires this risk calculation to be performed and reported without consideration of risk management. There is no predetermined allocation of the TRV in a 'forward driven' assessment of risk. The proportion of risk contributed by each media and exposure pathway should be identified on a purely science basis in order to inform risk management decisions.

As a second step, a proposed property specific standard may be back-calculated, using the same exposure equations, to propose a cleanup standard for those contaminants which exceed an acceptable level of risk. Alternatively, risk management measures may be proposed which alter the exposure equations resulting in a reduced estimate of risk. In these cases, the regulation limits the proportion of risk which can be allocated to any single source of exposure (i.e. limits the allocation of risk among environmental media).

Care should be taken in using back-calculations to estimate proposed property specific standards, as these calculation do not necessarily account for physical/chemical limitations such as the formation of pure chemical compound. A contaminant concentration which has been determined to result in an acceptable level of risk to human health may be proposed as a human health - based property specific standard. However, the ministry also expects the proposed standard to reasonably represent an upper estimate of the actual concentrations remaining on the property at the time the standards are to be used to file a RSC (refer to Section 2.2.1 of this procedure document).

Additional guidance on meeting these requirements are provided in the following sections of this procedures document.

4.4.1.1 Non Threshold Effects

For chemicals acting through mechanisms presuming the absence of a biological threshold (for examples selected carcinogens) an additional, or incremental, lifetime cancer risk of one-in-a-million (1 × 10^-6) must be applied to each environmental medium. An environmental medium, for the purpose of human health risk characterization, includes but may not be limited to soil, ground water, air, and garden produce. A receptor may be exposed to an environmental medium through one or more exposure pathways. For example, risk due to exposure to soil through the combined pathways of oral ingestion and dermal contact should not exceed 1 × 10^-6.

If an individual COC produces a systemic effect in which more than one pathway results in the same endpoint at the same target site, the sum of risk levels for those pathways should be no greater than 1 × 10⁻⁶. This applies whether or not the pathways arise from the same medium. Both systemic and local effects may be assessed and considered separately, subject to the availability of toxicity data from a credible agency.

By definition, an incremental lifetime cancer risk is additional to background risk. For most COCs, the calculation of risk due to background exposure is not required as part of risk assessments; however, background exposure should be considered for COCs, which are above the 1 × 10⁻⁶ risk.

4.4.1.2 Threshold Effects

For chemicals (including some carcinogens) acting through mechanisms that presume a biological threshold, potential adverse health effects should be evaluated and characterized by comparing an exposure level over a specified period of time (for example, lifetime) with an appropriate TRV derived for a similar exposure period.

One contaminant source or source/pathway combination typically dominates exposure. No more than 20% of the reference dose should be apportioned to each environmental medium (acceptable Hazard Quotient may not exceed 0.2 for each medium) using the following formula:

Hazard Quotient (HQ) = exposure level ⁄ TRV

An environmental medium, for the purpose of human health risk characterization, includes but may not be limited to soil, ground water, air, and garden produce. A receptor may be exposed to an environmental medium through one or more exposure pathways. For example, the Hazard Quotient due to exposure to soil through the combined pathways of oral ingestion and dermal contact should not exceed 0.2. Implicit in this interpretation is that the sum of exposure from all sources, including background exposure, cannot exceed the TRV.

Air, as an example, is considered a source medium with 20% of the TRV allocated to the sum of potential indoor and outdoor inhalation pathways. Note that modelled transport of contamination in the vapour phase originating from soil and groundwater are not considered additive. The source of contamination in vapour is either soil or groundwater, but not both at once, at a single location. A property specific standard proposed for soil should result in no more than 20% of the TRV allocated to exposure to vapours volatilized from soil. A property specific standard proposed for ground water should result in no more than 20% of the TRV allocated to exposure to vapours volatilized from ground water.

The QP_RA is encouraged to consider allocation of 20% of the TRV per medium in developing the proposed property specific standard (which may include risk management) as standard practice consistent with the development of the ministry generic site condition standards. The purpose is to ensure that the source of exposure which determines the acceptable concentration of the standard contributes no more than 20% of the total acceptable exposure. Other sources are therefore expected to fall automatically below 20%. The allocation does not have to be equally divided among pathways for a given medium provided that the total for each medium does not exceed 20%. Where several pathways contribute to exposure from a single medium, the dominant pathway should be used to calculate the standard. Iteratively adjustment to the dominant pathway may be necessary to ensure that the total from that source does not exceed 20%.

Other allocations are also allowed under the regulation providing they are justified through a detailed multi media assessment of exposure (such as the forward driven assessment) and the total exposure does not exceed the TRV. If there is any deviation from the apportionment of 20% to any environmental medium, a fully developed rationale including property-specific multimedia exposure assessment must be provided.

Explicit calculation of health effect risk due to background exposure is not generally required as part of risk assessment. Background exposure could be considered for some COCs where it is known to be significant. QP_RA's are requested to contact the ministry for guidance in such cases.

4.4.1.3 Application of Toxic Equivalency Factors to Evaluate Contaminant Groups

The ministry has selected a Toxicity Equivalency Factor (TEF) approach as the basis for standardizing the toxicity of structurally similar compounds displaying similar toxicity profiles. Examples include dioxin-like compounds and carcinogenic polycyclic aromatic hydrocarbons (PAHs).

The index chemical selected for the assessment of dioxin-like compounds is 2,3,7,8-TCDD. TEFs for dioxin-like compounds are provided in Appendix A to this Procedures document.

Risks resulting from exposure to the carcinogenic PAHs are considered additive and should not exceed 1 × 10^-6 for all exposure pathways and media combined. These compounds exhibit a systemic effect in which more than one pathway results in the same endpoint at the same target site.

Health effects should also be aggregated for the non-carcinogenic PAHs whose individual components elicit similar mechanisms of toxic action. These aggregated risks should not exceed a target HQ of 0.2.

It is recommended that proponents assessing PAHs contact the ministry for further information concerning acceptable approaches. A proposed approach may be specified in the Pre-Submission Form or advice may be sought directly through the ministry Risk Assessment Coordinator.

For other COCs which do not have a similar mechanism of toxic action, the aggregation of risks will not be required. Similarly, pathway hazard quotients of contaminants for which the exposure limits are based on different adverse effects and mediated by different mechanisms of action should not be added. However, this approach is acceptable when adequate evidence suggests it is appropriate to aggregate risk levels to account for systematic effects in which multiple chemicals act by the same toxicity mechanism and/or on the same organs. These contaminants should be treated as a group and the target hazard quotient of 0.2 should be maintained.

Examples of contaminant groups that may be aggregated this way include but are not limited to chlorinated dioxins, PCBs, organophosphorus insecticides and some volatile organics. Various jurisdictions have published general guidelines on risk assessment of mixtures, such as Health Canada (1994) and US EPA (1986b; 2000). The QP_RA should exercise best professional judgment when using these guidelines and in deciding which contaminants should be treated as a group.

4.4.1.4 Adjustment for Absorption and Bioavailability

For quantitative risk characterization purposes, exposure and toxicity values should both be expressed as either absorbed doses or administered doses. Adjustments for bioavailability in different media should only be made where differences due to media are significantly greater than other receptor influences on uptake (for example, individual variation in nutritional status). Bioavailability adjustments based on human/animal studies are preferred to model predictions.

Bioavailability-related adjustments should be made in the context of the underlying animal or human study used for the RfD or other exposure limit (cancer slope factor) and should be justified scientifically.

Further guidance on bioavailability adjustments for human health risk assessment may be obtained from the ministry.

4.4.2 Qualitative Interpretation of Health Risk

The QP_RA may make use of both quantitative and qualitative options in assessing risk. A qualitative assessment of risk relies primarily on a descriptive justification for the use of information not specific to the site. In a qualitative analysis, the QP_RA should explain why a qualitative approach was used and justify why a quantitative analysis was not appropriate or not required. The QP_RA must also indicate the process to be used in the qualitative analysis; for example, a non-numeric (descriptive) characterization of risk or a conservative numeric assessment of exposure or toxicity for screening purposes and risk prioritization. Qualitative risk assessment must also address any risk management measures that are being proposed for the property, and justify a property-specific human health-based standard for the contaminant.

Examples of situations suitable for a qualitative interpretation of risk would include the following;

• Based on the results of the exposure assessment and the toxicity assessment, the full depth generic site conditions standards contained in Table 2 of the document "Soil, Ground Water and Sediment Standards for Use Under Part XV.1 of the EPA" are protective of the sensitive site conditions (including shallow water table) at the site;
• Based on the results of the exposure assessment and the toxicity assessment, the human health component values contained in the document Rationale for the Development and Application of Generic Soil, Ground Water and Sediment Criteria for use at Contaminated Sites in Ontario (MOE, 1996) are protective of the human receptors at the site.

The minimum requirements for reporting a qualitative characterization of risk are reproduced from the RSC Regulation Schedule C Table 1, below.

4.4.3 Special Considerations for Environmentally Sensitive Areas

Whether a qualitative or quantitative assessment of risk is undertaken, any risk characterization considerations associated with the site being defined as an environmentally sensitive area must be highlighted in a separate section of the report. The reason for the environmentally sensitive designation should be identified and the expected impact on the estimation of human health risk, if any, should be described.

The reason for the environmentally sensitive designation may be due to the presence of susceptible contaminant transport pathways which may enhance human exposure to contaminants. If this is the case, this section of the RA report should reference how the susceptible pathways are addressed and indicate how the human health standards proposed for the site are expected to be protective of human exposure through those pathways.

Minimum requirements for reporting special considerations for environmentally sensitive areas in the RSC Regulation Schedule C Table 1 are reproduced below.

4.4.4 Interpretation of Off-Site Impacts to Human Health

Whether a qualitative or quantitative assessment of risk is undertaken, the QP_RA must highlight in a separate section of the report any considerations associated with off-site human receptors. Specifically, the QP_RA must indicate if the proposed human health standards, if applied to the RA property are expected to be protective of those off-site receptors.

The minimum requirements for interpretation of off-site human health risks are found in the RSC Regulation Schedule C Table 1 and are reproduced below.

For each COC, the QP_RA must assess whether the human health standard being proposed for the RA property is likely to result in a concentration greater than the applicable full depth site condition standard at the nearest human receptor located off the RA property. If this is the case for any contaminant, the QP_RA must specify the contaminant, the applicable site condition standard for that contaminant and the property where the receptor is located and describe the human receptors that may be impacted.

For a given COC, the outcome from any off-site exceedance of the applicable full depth site condition standards resulting from the property will be determined by the ministry District Office, which will prioritize any action that may be warranted on a specific property on a case by case basis.

4.4.5 Discussion of Uncertainty

There are areas of uncertainty in both toxicity and exposure assessment. Minimum requirements for the discussion of uncertainty in risk characterization are provided in the RSC Regulation Schedule C Table 1 and reproduced below. Uncertainty of the overall risk assessment process should be quantified where appropriate and discussed explicitly, including the following:

• Description of the risks in terms of magnitudes and types of uncertainties involved,
• Interpretation of the significance on the overall assessment of risk, and
• Factoring of information on the uncertainty in risk estimates, be it overestimation or underestimation, into the risk management decision in designing a suitable risk reduction strategy.

Uncertainty related to the toxicity assessment includes the accuracy of the TRV considering available toxicity data, the use of uncertainty factors to account for route to route and species to species extrapolation and the use of relative absorption factors to account for bioavailability. The combined effect of uncertainty on the conservatism of the TRV should be discussed in terms of the identification of significant risks.

Uncertainty related to the exposure assessment includes the accuracy of predicted contaminant concentrations in environmental media based on the availability of measured, site specific data and the ability to predict human exposure to the contaminated media. The combined effect of uncertainty on the exposure estimate should be discussed in terms of the possibility of a significant risk to go undetected and whether the risk should be managed in the absence of reliable data.

Section 5. Requirements Specific to Ecological Risk Assessment

5.1 Levels of Assessment for ERA

The basic structure for conducting ERAs in Ontario is founded upon the CCME's ecological risk assessment framework. For detailed descriptions of the steps or components for the different levels of ERA, and for more detailed guidance on conducting ERAs, the QP_RA is referred to the CCME document entitled "A Framework for Ecological Risk Assessment: General Guidance" (CCME, 1996), and to "A Framework for Ecological Risk Assessment: Technical Appendices" (CCME, 1997). It should be noted that ERA "triggers", which are listed on page 3 of CCME (1996), are good indicators of when a site should be considered 'sensitive'. These 'triggers' justify the use of a risk assessment approach rather than the use of site condition standards. However, once a risk assessment approach has been selected under the RSC Regulation, these triggers cannot be used to justify the requirement or absence of an ERA. The ERA process below should be followed for all risk assessments which are submitted under the RSC Regulation.

Persons conducting ERAs should be familiar with the CCME ERA procedures and documents above, as well as more recent documents that may be of assistance in conducting ERA such as those listed in the bibliography in Section 9 of this Procedures document.

The ministry advocates three levels of investigation of potential ecological risk as follows:

1. A Screening Level Ecological Risk Assessment (SL-ERA) is a primarily qualitative assessment of the potential environmental risk to specific ecological receptors that have been determined to be of major importance, i.e., valued ecosystem components (VECs). A SL-ERA is based primarily on data from literature reviews and from previous or preliminary studies at the property. It should provide sufficient information to determine that remediation is or is not required to protect ecological receptors, or it may provide a basis for determining what additional level of ERA is required and for focusing more detailed investigations of potential effects. If the SL-ERA concludes that remediation is not required, the QP_RA must propose a property-specific site condition standard based on the outcome of the SL-ERA such as the maximum concentration of the COC at the RA property.
2. A Preliminary Quantitative Ecological Risk Assessment (PQ-ERA) uses a combination of literature information and property specific data which may be collected specifically for ERA purposes, to determine preliminary quantitative risk estimates for specified VECs exposed to the COCs. A PQ-ERA is focused on filling significant data gaps identified at the screening level. Methods used for a PQ-ERA are more complex than for a SL-ERA and are directed at producing quantitative assessments of risk.

   At this level of assessment, bioassays and/or biological field studies can be useful tools for assessing the toxicity of the contaminants present at the RA property. In the large majority of cases where this level of assessment is used, it should produce sufficient information upon which property-specific site condition standards can be proposed for use in remediation. In a few cases, data gaps or uncertainty may be of sufficient concern to warrant still more detailed investigations.

3. A Detailed Quantitative Ecological Risk Assessment (DQ-ERA) uses more extensive and complicated field assessments, biological field studies and modeling of contaminant movement, exposure pathways, ecosystem characterization and assessment of toxicity to attempt to fill significant data gaps and uncertainties already identified, and to quantitatively assess risk. Bioassays or field surveys are likely to be important tools in assessing toxicity at this level of assessment.

An ERA should begin with an SL-ERA and may progress through the more detailed levels of assessment if property characteristics so warrant. The QP_RA and risk assessment team should do the following:

• Determine whether the site would be considered "environmentally sensitive", according to Section 41 of the RSC Regulation,
• Determine which level of assessment is appropriate for the RA property,
• Include at least one of the three levels of assessment in the ERA for each COC and justify the choice in the RA report, and
• Provide and justify a property specific standard for each COC for the VEC determined through the risk assessment process to be most at risk due to the presence of the COC.

5.2 Problem Formulation Component of ERA

The problem formulation component of the ERA comprises a description of the conceptual site model as it relates to ecological receptors and identification of the ERA objectives based on that model. Minimum requirements for reporting the Problem Formulation are provided in Table 1 Schedule C of the RSC Regulation, and are reproduced below.

Additional guidance is provided in the following sections of this procedures document.

5.2.1 Ecological Conceptual Site Model

The ecological conceptual site model is a physical description of the potential contamination problem from an ecological risk perspective. The ecological conceptual site model must meet the requirements of the RSC Regulation as described in Schedule C Section 3(8)(b) and (c) and Table 1 Report Section 5 "Ecological Risk Assessment". Potential receptor populations for the proposed property use must be identified along with all associated potential exposure routes and pathways. For each of the sources of COCs for the RA property, the QP_RA must ensure that the conceptual site model identifies:

1. the release mechanisms and transport pathways and
2. all ecological receptors located both on and off the RA property, as well as exposure points and routes of exposure.

Ecological receptors may be described as a group rather than individual species where appropriate. For example, "garden vegetables" may be identified as an ecological receptor group, rather than listing individual vegetables. It is appropriate, however, to list individual species where these species are the basis for designation of an "Environmentally Sensitive Area" under section 41 of the RSC Regulation.

The ecological conceptual site model must identify potential exposure pathways for those receptors based on physical/chemical characteristics of the COCs and geological characteristics of the site as identified in the subsurface transport component of the conceptual site model in Report Section 3.

The ecological conceptual site model must clearly distinguish between pathways which are naturally incomplete and those which may be rendered incomplete through risk management measures.

For each applicable receptor, the RA team should identify all potential on-site and off-site exposure pathways (for example soil ingestion) based on the characteristics and anticipated activities of that receptor and the expected mobility of the potential COCs under the geological conditions present at the site. For each receptor and exposure pathway, the RA ream should indicate further if a man-made barrier or measure to interrupt this pathway is present or anticipated.

Any exposure pathways which can be anticipated based on chemical properties and site geology should be included in the risk assessment. Elimination of these pathways from assessment will require justification in the form of pathway-specific site assessment evidence. Pathways which can be anticipated but which will be mitigated by a barrier or other measure should be included for the assessment of risk level. The barrier or other measures must be identified as risk management measures in the development of property-specific criteria.

5.2.2 Risk Assessment Objectives

As is the case for HHRA, the QP_RA must provide risk assessment objectives which describe the approach to studying the potential contamination problem (refer to Section 3.2 of this Procedure document) with reference to the ecological conceptual site model (Section 5.2.1) and demonstrate that data used in the ERA are sufficient to meet those objectives. It is important to state whether the RA is a qualitative or quantitative assessment of risk and the type of approach used for the ERA.

Examples of ERA Objective Statements would be;

• Example 1:

  "The objective of the ERA is to provide a qualitative demonstration that the Table 2 site condition standards are appropriate to protect ecological receptors at this site using a limited scope risk assessment and modified generic approach. The site is located in an Environmentally Sensitive Area according to Section 41 of Ontario Regulation 153/04 due to the proximity of a surface water body. The proposed land use is high rise residential in an urban setting. The valued ecosystem component to be protected is a stream habitat within the property boundary.

  On-site terrestrial habitat will be largely disturbed through paving and construction of underground parking facilities. The Table 2 site condition standards will be protective of urban lawns and gardens in potential green spaces. The surface water pathway for migration of contaminated soil will be justified as incomplete.

  The pathway of concern in this ERA is migration of contaminants to the stream through the groundwater pathway and exposure to benthic and aquatic organisms. Receptors to be assessed in the stream will include fish, aquatic plants and benthic organisms. Due to the presence of fish spawning habitat in the immediate vicinity of the site, the assessment endpoint for fish VECs will be reproduction success; whereas growth and survival will be the targeted assessment endpoints for both the aquatic vegetation and benthic VECs."

• Example 2:

  "The objective of the ERA is to provide a quantitative evaluation of risk of 1,3,5-trinitro-1,3,5-triazine (RDX), a chemical for which there is no site condition standards, and to propose an ecological risk-based Property Specific Standard using a New Science risk assessment approach. The proposed property use is for single family residential. There is no groundwater use on site, drinking water is provided through a municipal water supply.

  VECs and exposure pathways to be evaluated include:

  • Soil uptake by ornamental plants and garden vegetable plants and direct soil contact exposure to soil invertebrates. VECs will include lawn grasses and earthworms;
  • Direct contact with soil, soil ingestion and inhalation exposure to terrestrial animals. VECs will include rodents and song birds that frequent residential neighbourhoods (i.e. grey squirrel, robin);
  • Assessment of the inhalation exposure pathway will be qualitative due to lack of a suitable TRV;
  • Contamination of groundwater and surface water and migration of contaminants to off-site ecological receptors. VECs will include fish, aquatic plants and benthic organisms.

  For each of the above VECs the assessment endpoint will be survival and growth."

5.2.3 Discussion of Data Quality

As indicated in the table above, the RSC Regulation requires that the QP_RA demonstrate that the data used for the ERA and described in Section 3 of the RA report is sufficient to meet the objectives of the assessment. Data quality or availability may be insufficient for a quantitative assessment, for example, and a qualitative approach may be proposed. Examples of data quality problems which may impact on the risk assessment approach include;

• Detection limits below the ministry site condition standard value (selection of COC),
• Low analytical recovery,
• High relative standard deviation,
• Variable monitoring data, inconsistent year-to-year trend,
• Assumption for one or more pathway relies on old data, data based on analytical method that does not comply with section 47 of the regulation, insufficient monitoring or no supporting data.

Uncertainty in the data resulting from variable or poor data quality, as well as any data gaps should be discussed in terms of the RA approach used to accommodate them. The QP_RA should explicitly discuss the extent to which suspect data can and will be relied upon in the RA.

5.3 Receptor Characterization

Minimum requirements for reporting Receptor Characterization are provided in Table 1 Schedule C of the RSC Regulation, and are reproduced below.

Additional guidance is provided in the following sections of this procedures document.

Receptor characterization for ERA should identify and characterize the ecological receptors of concern and the degree to which they must be protected. Receptor characterization should address:

• Multiple ecological receptors,
• Potential exposure pathways, and
• Potential environmental impacts.

The QP_RA should consider receptors for the ERA including but not limited to terrestrial plants, terrestrial animals and soil dwelling organisms, aquatic species that could be affected through surface water or ground water discharging to surface water and avian species that may be affected by contamination at the RA property. The CCME document "A Framework for Ecological Risk Assessment: General Guidance" (March 1996) provides the following guidance for identification of VECs;

"VECs are resources or environmental features that

• Are important to human populations,
• Have economic and/or social significance,
• Have intrinsic ecological significance,
• Serve as a baseline from which the impacts of development can be evaluated, including changes in management or regulatory policies."

For the purpose of the RSC Regulation, potential receptors on and off site should be evaluated as VECs on the basis of importance or significance at the scale of an individual property owner. The ability to provide a lawn or ornamental garden may be economically or socially significant to an individual property owner, whether or not it is significant at a regional or provincial level.

The Receptor Characterization should provide for support of VECs at least to the extent of supporting landscaping and green space. If a decision has been made by the property owner to develop the site in such a way that landscaping and green space are eliminated through paving or other construction, the risk to landscaping and green space should still be assessed. The effect of paving or other construction should be accounted for as a risk management measure. In this way, future property development decisions (by future owners, for example) will be made with an appreciation of the ability of the site to support landscaping and green space. If there is uncertainty related to the design of future development and how it may impact ecological receptors, this should be addressed in the risk assessment report under the heading Discussion of Uncertainty.

Any endangered or threatened species on-site or off-site should be listed (including common and species name).

Considering the habitats present and based on observations both on and off site, identify individual species representing Valued Ecological Components (VECs) including the terrestrial and aquatic species to be studied. Off-site VECs are to be considered if their range area is within an area of potential contaminant impact. The area (distance) characterized by 'off-site' should be based on the species range area.

Receptor Characterization should identify the VECs, the effects against which it is desirable to protect the VECs and the pathways specific to each VEC by which it may come into contact with contaminants. The Receptor Characterization process should document the following:

• The VECs (species or habitats) that the ERA should protect,
• The effects that the ERA should protect these species against (referred to as "assessment endpoints"),
• The measurements that can be used to assess the effects (referred to as "measurement endpoints"), and
• The characteristics of the VECs that influence their exposure to the potential contaminant.

If surrogate species are to be used in the study of the VECs, these should be clearly identified together with the VEC species they are to represent.

The QP_RA should include the following considerations:

• The current use of the RA property, distance to the closest receptor and receptor activities and patterns (including but not limited to the proportion of time the potentially exposed populations spend in the area; variation due to seasonal changes; any property-specific population characteristics that might influence exposure; and what ecological habitats exist on-site);
• Future use of the RA property, use of the ground water under future conditions, and potential for more or different habitat to ecological receptors (including, but not limited to, changes in the proportion of time the potentially exposed populations spend in the potentially contaminated area; population characteristics and ecological habitats);
• The receptor sub-populations of potential concern: any group with increased sensitivity, either due to, for example, the behaviour, activity pattern or health status of the sub-population or to the inherent toxicity of the COC; distance to specific valued ecosystem components (VECs), including threatened or endangered species, at or near the property; and
• Uncertainty that exists in terms of characterization of complete exposure pathways and potential receptors (extent and quality of supporting site data, understanding of proposed land use and knowledge of uses and likely uses of adjacent or potentially impacted sites).

5.4 Exposure Assessment

Exposure assessment is a detailed analysis of the potential contamination problem as described in the ecological conceptual site model (section 5.2.1 of this procedures document). Exposure Assessment for ERA must evaluate the potential exposure of the VECs to contaminants determined to be of potential concern. Qualitative or quantitative exposure assessment may be undertaken according to the RA objectives as described in sections 3.2 and 5.2.2 of this procedures document. Methods of estimating exposure point concentrations (including but not limited to modelling of contaminant movement) should be compatible with those used for HHRA (i.e. the hygrogeological interpretation and method of calculation of exposure point concentration via transport modelling must be consistent for both ERA and HHRA).

Minimum requirements for the Exposure Assessment component of the ERA are provided in Table 1, Schedule C of the RSC Regulation, and are reproduced below.

Further guidance is provided in the following sections of this procedures document.

5.4.1 Pathway Analysis

In the RA report the pathway analysis must identify the exposure routes and pathways considered potentially complete or complete without risk management measures. Any exposure pathways which can be anticipated based on chemical properties and site geology should be included in the exposure assessment. Elimination of these pathways from assessment will require justification in the form of pathway-specific site assessment evidence. Pathways which can be anticipated but which will be mitigated by a barrier or other measure should be included for the assessment of risk level. The barrier or other measure must be identified as risk management measures in the development of property-specific criteria. The analysis should address the exposure pathways of concern, including exposures via all potential media, and considering the current and/or future condition of the RA property without risk mitigation measures, including the following:

• Exposure pathways of concern according to the ecological conceptual site model (Section 5.2.1 of this procedure document);
• The sources for all potential releases (past, present and future);
• The potential receiving media (air, surface water, ground water, soil, sediment, biota), and
• Evaluation of the physical and chemical fate and transport properties of the COC to identify the media that are receiving or may receive the property-related contaminant;
• The exposure points (i.e., where the potentially exposed population can contact the COC);
• The exposure routes (could include but not limited to ingestion of soil/water and/or food, inhalation of vapour, inhalation of soil particles and dust, dermal contact with soil/water and other routes that may be associated with the contaminated media).

The following points should be considered when evaluating exposure pathways.

• Discuss the environmental fate of the contaminants including possible degradation. When sufficient laboratory and field evidence indicates that a contaminant could be degraded/biodegraded (transformed/biotransformed) to a relatively more toxic and persistent intermediate/product, the future concentration of the potential degradation product/intermediate should be estimated from the present concentration of its precursors, if possible (for example, the anaerobic biodegradation of chlorinated aliphatics in ground water).
• Identify direct and indirect routes (via intermediate receptors such as food/prey) and pathways of exposure for each VEC.
• Taking into account the proposed property use, plans for construction and the fate and transport of the contaminant in the environment, identify and document relevant exposure scenarios and exposure route/pathways to on-site and off-site VECs.
• Justify the exclusion (if any) of receptors and exposure route/pathways associated with development of the component values for the full depth generic site condition standards (Rationale for the Development and Application of Generic Soil, Ground Water and Sediment Criteria for use at Contaminated Sites in Ontario, 1996 MOE).

5.4.2 Exposure Estimates

The exposure assessment should document the contaminants of potential concern to be assessed for specific VECs and follow through with pathway analysis and quantification.

In some cases a qualitative approach may be taken to exposure estimation by using highly conservative (screening level) exposure estimates or estimates based on the ministry generic exposure scenario (Rationale for the Development and Application of Generic Soil, Ground Water and Sediment Criteria for use at Contaminated Sites in Ontario, 1996 MOE) rather than developing site specific exposure estimates. The qualitative assessment of risk must provide a descriptive justification for the use of information not specific to the site. The justification should indicate why site specific information was not measured or not quantifiable for the purpose of the risk assessment and why the substitute information is appropriate. This approach would be suitable if it meets the risk assessment objectives identified in Report Section 5 of the RA report.

In many cases, quantification of exposure estimates will be required to meet the risk assessment objectives. Quantification of the exposure to the receptors refers to the calculation of intake or uptake rates or delivered target dose for each exposure pathway/route and the total aggregate exposure if relevant. Quantification of the contaminant intake and uptake should be done for each potentially complete exposure pathway. Quantification should include the following information:

• Exposure concentration that is contacted over the exposure period at the external exposure point for each pathway,
• Contact rate (amount of contaminated medium contacted per unit time or event) and/or absorption rate, and
• Total time of exposure (estimated from exposure frequency and duration).

Reasonable maximum as well as average estimates of exposure or distribution for relevant populations should be developed based on both current and future property use assumptions, and measured concentrations on the property.

Care should be taken if COC concentrations are characterized with an estimate of the average of the data; i.e. using the 95% UCL above the mean concentration, which is often used in HHRA. The range of the animal or bird VECs should be taken into consideration, as should the area of the site that might be considered foraging habitat. The use of a one sided 95% UCL for the mean is not justified for vegetation or soil organisms which are essentially immobile. Rather, consideration should be given on a sample location-by-location basis to the areas of the site which exceed a given TRV. It is acknowledged that a risk assessment for plants and soil organisms is not meant to protect individuals. The ecological significance of the spatial distribution of exceedances of a TRV therefore should be evaluated. It should be noted that any methods chosen for use in the development of property-specific standards should be determined by the quality and quantity of data available.

Fate and transport models are frequently used to predict the likely current extent of contamination as well as to assess the behaviour of contaminants under potential future scenarios. Such modeling can be useful to direct sampling programs and draw conclusions regarding off site migration of contaminants. When a fate/transport model is utilized in the RA to predict contaminant concentrations in soil or groundwater, the predicted concentrations should be verified through field sampling wherever possible.

Quantification may also include exposure from other sources/pathways/routes not specifically associated with the RA property, such as food ingestion, water supply and ambient air (i.e., typical background exposures) if sufficient information is available.

In conducting quantitative exposure assessment the following should be considered;

• Document the exposure models, model assumptions and characteristics of the VECs, used for evaluation of exposures.
• Provide general equations and sample calculations for evaluating VEC exposure for the various pathways.
• Calculate exposures to the different VECs from various pathways identified for different contaminants.
• Consideration of background exposures other than exposure to on-site contamination (soil, air, water, etc.) should also be discussed with reference to the property specific exposure.
• Analysis of the major sources of uncertainty and how they affect (quantitatively, if possible) the exposure estimates. Uncertainty in the pathway analysis, for example, should be discussed in terms of the dependency of the exposure estimates on pathway assumptions that are unconfirmed or beyond the knowledge and control of the proponent.

If computer models are utilized, ensure the models have been validated and/or are considered acceptable based on scientific principles. These models should also be available in the public domain. Use of proprietary models may be considered only when sufficient documentation of the modelling is provided and may require additional ministry review as provided by the regulation (refer to Schedule C, Section 9 of the RSC Regulation). Such models (validated and/or accepted) should be accompanied by available technical support documentation of basic principles, user instructions, etc. The documentation should include all mathematical expressions and assumptions used in the model(s).

If proprietary models and any supporting documentation are considered confidential, such material should be clearly marked confidential. In either case, review of a RA report will be facilitated by provision of any computer software being utilized for the exposure calculations. The ministry will require evidence that such software models are provided in a manner that will not infringe any third person’s copyright. The rationale for the suitability of any chosen model to the problems posed by a property should also be documented (refer to Section 7.3.2 of this procedure document).

When conducting probabilistic modelling, statistical distributions developed from site-specific data or obtained from published peer reviewed scientific literature applicable to the site in question should be used for parameters associated with receptor characteristics (refer to Section 7.3.3 of this procedure document). The statistical distribution used in probabilistic modelling may require additional ministry review, as provided by the regulation (refer to Schedule C, section 9 of the RSC Regulation).

5.5 Hazard Assessment Component of ERA

The section in the RA report pertaining to hazard assessment should provide documentation relating to the nature of toxicity and dose response for each COC as they apply to VECs (exposed individuals or populations) including:

• The potential adverse effects on the VECs associated with exposure to the specific contaminants, and
• The relationships between the magnitude of exposure from relevant exposure pathways and the probability of occurrence of adverse effects on the receptors.

Minimum requirements for the Hazard Assessment component of the ERA are provided in Table 1 Schedule C of the RSC Regulation, and are reproduced below.

The QP_RA must identify the potential adverse effects (endpoints) selected for each chosen VEC (for example mortality, growth, reproduction).

Ministry TRVs published in the Rationale for the Development and Application of Generic Soil, Ground Water and Sediment Criteria for use at Contaminated Sites in Ontario (1996 MOE) should be used in preference to toxicity values from other jurisdictions unless there are values published more recently by a credible agency. A search of the most recent toxicity data should have been conducted within two years prior to submission of the RA report. For those contaminants for which the ministry has not developed any TRVs, values published by other credible regulatory agencies may be used.

Toxicity values published by the CCME in Canadian Soil Quality Guidelines supporting documents (publications specific for individual contaminants) and toxicity values published by the US EPA for Ecological Soil Screening Levels are generally considered acceptable to the ministry with limited review. Toxicity values from other sources for contaminants without ministry site condition standards may require additional ministry review as provided by the regulation (refer to Schedule C, section 9 of the RSC Regulation). The ministry will notify the QP_RA as soon as practical if any ecological toxicity values proposed for use in a risk assessment are subject to the 22 week review timeline.

Credible agencies are those which have incorporated the following in developing TRVs:

• A rigorous peer review mechanism by credible experts/multiple regulatory bodies/jurisdictions and/or academia,
• Ongoing review and updating of values on the basis of new studies or advances in science, and,
• Published and/or publicly available TRV values, together with the basis for the value selection.

Examples of credible agencies include but are not limited to CCME, US EPA, Oak Ridge National Laboratory. If the data from a credible agency is utilized, the data should be accompanied by:

• A discussion of the rationale used by the agency in the choice of data and the critical study,
• A description of how the considerations of the agency are applicable to the receptors and site conditions of the RA property (for example dose- response model, uncertainty factors, etc.),
• Documentation of the description and evaluation of the toxicity assessment and provision of a rationale for adopting that particular toxicity assessment.

The ministry also supports the development of new ecological TRVs based on the best available science. TRVs should be developed using the following process:

• A search of toxicological databases for toxicological literature pertaining to the given chemical parameter and VECs of interest;
• A review of the quality of the studies and their applicability to the RA property;
  • Selection of a LOEL, from existing dose-response data;
  • Selection of a NOAEL for threatened or endangered species.

In selecting toxicity data from which a TRV is derived, preference will be given to:

• Toxicity data derived from the species which are closely related to each VEC (for example laboratory mouse data for small mammals, quail data for grouse);
• Feeding studies using multiple exposure levels (not single dose, or gavage, or injection studies);
• Chronic exposure studies, particularly over several months duration, and/or over sensitive life stages (for example during reproduction); and
• Studies which evaluate a reproductive endpoint (for example number of live births, number of eggs hatched) - these data are preferred as these assessment endpoints most closely relate to wildlife success.
• Secondary preference will be given to survival and growth data.

For the levels of ERA other than the SL-ERA, bioassays or field surveys may become important tools for hazard assessment. If bioassays or field surveys are conducted, they should:

• Be chosen to include species and endpoints that are relevant to the property being assessed and that are known or thought to be sensitive to the potential contaminants, and
• Include generally accepted standardized procedures and species.

A lack of sufficient relevant data should lead to the following conclusions:

1. The present status of scientific knowledge does not allow for the quantitative evaluation of ecological risk, and
2. No property specific ecologically based standard can be established.

Recommendations can be made that, for the protection of the natural environment and in the absence of adequate knowledge of ecological risk, exposure to environmental receptors be reduced as much as possible and property-specific site condition standards be based on other factors (for example the full depth background site condition standards in Table 1 of the Soil, Ground Water and Sediment Standards). When no site condition standard exists for a given chemical parameter, the property owner may choose to adopt a background-based or effects-based soil or groundwater value from another credible regulatory agency. Under the RSC Regulation, adopting a standard or guideline for environmental media (soil, water, air, sediment, garden produce) from another jurisdiction, if there is no ministry site condition standard, is considered a new science risk assessment (refer to Schedule C, section 9 of the RSC Regulation).

5.6 Risk Characterization Component of ERA

The section in the RA report relating to ecological risk characterization should document the following:

• An estimate of the degree of risk that is present from specified contaminants to the VECs present, or which will be present, at a property.
• A property specific site condition standard that results in the same level of risk to the environment intended by the generic site condition standards. In some situations, the resulting property specific standard will be a site condition standard validated for use at a sensitive site.

Measured and predicted contaminant concentrations are compared with toxicity information to determine the potential for adverse effects. Minimum requirements for the Risk Characterization component of the ERA are provided in Table 1 Schedule C of the RSC Regulation, and are reproduced below.

Additional guidance is provided in the following sections of this procedures document.

5.6.1 Quantitative Interpretation of Ecological Risk

When a quantitative assessment of health risk is the objective of the ERA, the minimum requirements, as specified in the RSC Regulation Schedule C Table 1 (reproduced below), are to be included in the RA report. Additional guidance on meeting these requirements are provided in the following sections.

If a quantitative analysis of toxicity and/or exposure assessment has been undertaken, contaminant-specific toxicity information must be compared against measured contaminant exposure levels and levels predicted through fate and transport modeling from which risk values can be derived.

A comparison of the TRV identified through hazard assessment (as described in section 5.5) with the exposure estimate (section 5.4 of this procedure document) provides a 'forward driven' science-based estimation of risk. The regulation requires this risk estimation or calculation to be performed and reported without consideration of risk management.

As a second step, a proposed property specific standard may be back-calculated, using the same exposure equations, to propose a cleanup standard for those contaminants which exceed an acceptable level of risk. Alternatively, risk management measures may be proposed which alter the exposure equations resulting in a reduced estimate of risk.

Care should be taken in using back-calculations to estimate proposed property specific standards, as these calculations do not necessarily account for physical/chemical limitations such as the formation of pure chemical compound. A contaminant concentration which has been determined to result in an acceptable level of risk to the environment may be proposed as an ecological effects-based property specific standard. However, the ministry also expects the proposed standard to reasonably represent an upper estimate of the actual concentrations remaining on the property at the time the standards are to be used to file a RSC.

5.6.2 Qualitative Interpretation of Ecological Risk

The QP_RA may make use of both quantitative and qualitative options in assessing risk. A qualitative assessment of risk relies primarily on a descriptive justification for the use of information not specific to the site. In a qualitative analysis, the QP_RA should explain why a qualitative approach was used and justify why a quantitative analysis was not appropriate or not required for a given VEC. The QP_RA must also indicate the process to be used in the qualitative analysis; for example, a non-numeric (descriptive) characterization of risk or a conservative numeric assessment of exposure or toxicity for screening purposes and risk prioritization. Qualitative risk assessment must also address any risk management measures that are being proposed for the property, and justify a property-specific ecological effects-based standard for the contaminant.

The minimum requirements for reporting a qualitative characterization of risk are reproduced from the RSC Regulation Schedule C Table 1, below.

Examples of situations suitable for a qualitative interpretation of risk would include the following;

• Based on the results of the exposure assessment and the toxicity assessment, the full depth generic site conditions standards contained in Table 2 of the document "Soil, Ground Water and Sediment Standards for Use Under Part XV.1 of the EPA" are protective of the sensitive site conditions (including shallow water table) at the site.
• Based on the results of the exposure assessment and the toxicity assessment, the ecological component values contained in the document Rationale for the Development and Application of Generic Soil, Ground Water and Sediment Criteria for use at Contaminated Sites in Ontario, (1996 MOE) are protective of the ecological receptors at the site.

5.6.3 Special Considerations for Environmentally Sensitive Areas

As indicated in the table below, the ecological standard being proposed for the RA property must ensure that the standard is protective of the conditions that cause the area to be an environmentally sensitive area as described in Section 41 of the RSC Regulation.

Whether a qualitative or quantitative assessment of risk is undertaken, any risk characterization considerations associated with the site being defined as an environmentally sensitive area must be highlighted in a separate section of the report. The reason for the environmentally sensitive designation should be identified and the expected impact on the estimation of ecological risk for each VEC should be described.

The reason for the environmentally sensitive area designation may be due to the presence of or proximity to specific ecological receptors, such as threatened or endangered species or ecosystems. If this is the case, this section of the RA report should reference how the specified ecological receptors are addressed in the VECs and how the ecological standards proposed for the site are expected to be protective of those receptors.

5.6.4 Interpretation of Off-Site Ecological Risks

Whether a qualitative or quantitative assessment of risk is undertaken, the QP_RA must highlight in a separate section of the report any considerations associated with off-site ecological receptors. The QP_RA must identify whether the proposed ecological standards, if applied to the RA property are expected to be protective of those off-site receptors.

The minimum requirements for interpretation of off site human health risks are found in the RSC Regulation Schedule C Table 1 and are reproduced below.

For each COC, the QP_RA must assess whether the ecological standard being proposed for the RA property is likely to result in a concentration greater than the applicable full depth site condition standard at the nearest ecological receptor located off the RA property. If this is the case for any contaminant, the QP_RA must specify the contaminant, the applicable site condition standard for that contaminant and the property where the ecological receptor is located and describe the ecological receptors that may be impacted.

As is the case for HHRA, for a given COC, the outcome from any off-site exceedance of the applicable full depth site condition standards resulting from the property will be determined by the ministry District Office, which will prioritize any action that may be warranted on a specific property.

5.6.5 Discussion of Uncertainty

There are areas of uncertainty in both hazard and exposure assessment. When conducting ERAs, it is often necessary to utilize results from dose-response studies using test species as surrogates for VECs selected for the RA property. Data in the literature may also be limited or incomplete such that it is necessary to extrapolate data for one endpoint to another (for example estimating a Lowest Observed Adverse Effects Level from LD50 data). These extrapolations add uncertainty to both the toxicity and exposure assessment.

Uncertainty related to the exposure assessment also includes the accuracy of predicted contaminant concentrations in environmental media based on the availability of measured, site specific data and the ability to predict VEC exposure to the contaminated media. The combined effect of uncertainty on the conservatism of the TRV and the estimated exposure should be discussed in terms of the significance of identified risks, the possibility of a significant risk to go undetected and whether the risk should be managed in the absence of reliable data.

Uncertainty in the ERA process should be quantified where appropriate and discussed explicitly, including the following:

• Description of the risks in terms of magnitudes and types of uncertainties involved,
• Interpretation of the significance on the overall assessment of risk, and
• Factoring of information on the uncertainty in risk estimates, be it overestimation or underestimation, into the risk management decision in designing a suitable risk reduction strategy.

Minimum requirements for the discussion of uncertainty in risk characterization are provided in the RSC Regulation Schedule C Table 1 and reproduced below.

Section 6. Risk Management (HHRA and ERA)

In the context of risk assessment conducted under Part XV.1 of the EPA, risk management refers to the development and implementation of one or more risk management measures which control or mitigate the level of risk to human health and the environment. The risk to be managed is that determined by other components of the risk assessment to be associated with contamination proposed to be left on a property after a Record of Site Condition has been submitted. Risk management involves the integration of the results from HHRA and ERA, including the uncertainty, with information about technical resources, social/economic factors and control options in order to decide how to manage the redevelopment of the property. This management decision may also include other factors and community input in some cases. Risk management is no longer categorized as Level 1 or 2 for the purpose fo filing a RSC.

The RSC Regulation provides for the QP_RA to make recommendations regarding the need for risk management to reduce either ecological or human health risk to acceptable levels. Risk management measures may include mechanical measures or techniques for reducing exposure, or eliminating or blocking exposure pathways. Examples of such methods include, but are not limited to:

• Utilizing a layer of clean soil above otherwise unacceptably contaminated materials to reduce exposure,
• The need for mechanical devices such as additional basement venting or pump and treat equipment to reduce exposure or to prevent movement of contaminants,
• The need for fencing off areas to prevent access to contaminated areas on a property, and
• The need for placement of pavement or other barriers on the surface to reduce exposure to contaminants.

Risk management measures also include administrative controls such as limitations on the use of the property that are outside of the normal restrictions for the type of property use to reduce exposure, eliminate or block exposure pathways due to contamination. Such limitations may require a certificate setting out the restrictions to be placed on the title of the property. Examples of limitations include, but are not limited to:

• Restrictions on the ability of the property to support plants or other forms of life that would be reasonably expected to occur on the type of property use involved, and
• Restrictions on the use of surface water or ground water from the property that is more limiting than would normally be expected for that property use.

Risk management may or may not be required if the property meets property specific standards. Risk management is required in those cases where the other components of the risk assessment identify that risk management measures are necessary to ensure that the recommended property specific standards result in an acceptable level of risk. When this is the case, the RA report must include a risk management plan which provides details about hydrogeological and engineering needs, as well as requirements for monitoring, maintenance, replacement and contingency.

Regulatory requirements of Risk Management Plans are contained in Schedule C of the RSC Regulation;

• Section 4 "Mandatory Requirements of Risk Assessment Reports"
• Table 1 Report Section 7 "Risk Management Plans"

If a risk management plan is included in the proposal for a property specific standard, the "Limited Scope Risk Assessment" alternative procedures will not apply, as specified in the RSC Regulation Schedule C Part II "Alternative Risk Assessment Procedures".

Certification statements are required for any proposed risk management plan, as specified in the RSC Regulation Schedule C Section 5 "Mandatory Certifications".

Accepted RAs may, at the Director’s discretion, have a control document known as a Certificate of Property Use associated with them. The need for a Certificate of Property Use (CPU) will be determined in consultation with the District Office. The content of the CPU may be influenced by the risk management plan and the level of risk controlled by risk management measures as determined from the RA. Risk management measures will also be reported in the Record of Site Condition (RSC) which is placed on the Brownfields Environmental Site Registry. Registration on title of the property may still be required in relation to property restrictions or requirements.

A CPU is a prescribed instrument under the Environmental Bill of Rights (EBR) and as such a proposal must be posted on the Environmental Registry for public comment. Therefore the QP_RA is asked to supply, at the time of an RA submission which proposes a risk management plan, a separate summary of the proposed risk management plan for posting on the EBR. When the summary is posted on the EBR, the wording as provided to the ministry will be posted as a control measure under consideration by the Director. The wording of the final CPU will be determined by the Director upon consideration of the risk assessment and any public comment.

Minimum requirements for a risk management plan are provided in Table 1 of the RSC Regulation, Schedule C, and are reproduced below.

The risk management component of a risk assessment must include, but may not be limited to the items discussed below.

6.1 Risk Management Performance Objectives

Risk management, if required, is necessary for recommended property specific standards to result in an acceptable level of risk. A risk management measure also must be maintained for some specified duration to ensure that the property specific standard continues to result in an acceptable level of risk. Performance objectives are measurable criteria against which the performance of the risk management measure can be evaluated to determine if the measure is meeting the required reduction in risk for the required duration of time. Where risk management is proposed, risk management performance objectives for each risk management measure must be clearly articulated within the RA report.

Performance objectives for risk management must include:

• The exposure pathway and target media that risk management measures must address, and
• The required reduction in exposure concentration that risk management measures must achieve.

The required reduction in exposure concentration should be determined based on an assessment of risk assuming no risk management measures. It should address the exposure pathways which contribute most significantly to unacceptable risk, or which can most efficiently be managed to reduce risk to an acceptable level. Identification of the reduction in exposure (for example expressed as a percent change or a target exposure route concentration or dose) is required for each managed pathway to achieve an acceptable level of exposure. Examples of risk management performance objectives include:

• Control of the vapour intrusion pathway to achieve a reduction in indoor air concentration from an estimated concentration of [specified] (determined without risk management) to an acceptable indoor air concentration of [specified].
• Control of the direct contact with soil pathway to achieve a reduction in surface soil / dust concentration from an estimated concentration of [specified] (determined without risk management) to an acceptable soil / dust concentration of [specified].
• Restriction of use of the property by refraining from [specified use or construction method] which would result in an estimated unacceptable dose of [specified] (determined without risk management) and thereby control the [specified] pathway and reduce exposure to [specified receptor].

The risk management objective should be stated in way which provides a criterion which is;

• Measurable through monitoring and record keeping,
• Suitable to trigger a specified contingency plan or other action, and
• Suitable for inclusion in a Certificate of Property Use.

6.2 Risk Management Measures and Ongoing Monitoring

The design and implementation of risk management measures must also be described and submitted in the RA report in the form of a risk management plan. Where additional site assessment is required to support the design and operation of risk management measures, this assessment should be clearly identified and documented.

The risk management plan may form a section within the RA report or may be provided as an Appendix to the RA report. If risk management measures include engineered controls, the design of such controls must be sealed or signed by a professional engineer within the regulation of the Professional Engineers Act, R.S.O. 1990, c.P28, as amended. If risk management measures include hydrogeological components, the plan must be sealed or signed in accordance with the requirements of the Professional Geoscientists Act. The risk management plan must include:

• Risk Management Measures to be implemented following achievement of the property-specific standard;
• Design and procedures for ongoing maintenance, monitoring and replacement of the risk management measures;
• A contingency plan; and
• Risk management responsibilities and obligations.

Where property characterization has identified the potential for risk to off-site receptors, the anticipated impact of the risk management plan on those off-site receptors must be described.

At the discretion of the Director, and in accordance with s. 168.6 of the EPA, a Certificate of Property Use may be issued to the owner of the property. Actions specific in the Certificate of Property Use may be based on the recommended actions proposed in the risk management plan.

Section 7. Alternative Risk Assessment Procedures

The ministry recognizes that the way in which the mandatory requirements of the risk assessment procedures described in this Procedure document are met may vary according to the situation for the development of a property specific standard. Certain approaches based on variations to the standard procedures have been identified by the ministry which would result in a risk assessment of less or greater complexity and either a shorter or longer time requirement for review. All regulatory requirements must be followed when conducting every risk assessment. However, certain risk assessment procedures may be modified to result in an alternative timeline as set out in the RSC Regulation.

In considering alternative risk assessment procedures, reference should be made to the RSC Regulation, and in particular to the following sections;

• Schedule C Part I "Mandatory Requirements"
  • Section 3 "Mandatory Requirements of the Pre-Submission Form"
  • Section 4 "Mandatory Requirements of Risk Assessment Reports"
  • Section 5 "Mandatory Certifications"
• Schedule C Part II "Alternative Risk Assessment Procedures"
• Schedule C Table 1 "Mandatory Requirements For Risk Assessment Reports"

Where combinations of alternative approaches are used in a risk assessment, the timeline for review will be determined by the approach requiring the longest timeline.

Further guidance on the use of these modified procedures is provided below.

7.1 Limited Scope Risk Assessment

Conditions which must be met for conducting a limited scope risk assessment are provided in Schedule C, Part II Section 7 of the RSC Regulation and are reproduced in the text box below:

Examples of situations in which a limited scope risk assessment might be considered appropriate by the QP_RA include, but are not limited to, the following;

• Contaminated ground water is 'flowing through' the property from a source of contamination on another property. Therefore, the QP_ESA believes that the property owner is not responsible for the contamination but must demonstrate that it does not interfere with the proposed use of the RA property;
• The QP_RA believes the full depth generic standards are appropriate as site condition standards due to specific characteristics of the site, even though the site qualifies as an environmentally sensitive area according to the regulation section 41 (for example due to proximity to a surface water body),
• The QP_ESA believes only minor changes to the generic conceptual site model are appropriate to account for specific characteristics of the property. The generic conceptual site model is described in the document "Rationale for the Development and Application of Generic Soil, Ground Water and Sediment Criteria for use at Contaminated Sites in Ontario" (MOE 1996) as updated from time to time, and was used in the development of the full depth generic site condition standards. Therefore, the QP_ESA and the QP_RA intend to use the ministry full depth generic standards model, with modification, to develop property specific standards. This is known as a modified generic approach.

If the situation allows for the use of a Limited Scope Risk Assessment (LSRA), then the following alternative procedures may be used in conducting that LSRA:

• In the Problem Formulation component of the LSRA, the receptors or property conditions which justify the LSRA should be clearly explained. Consultation with the body responsible for a sensitive receptor classification may be appropriate. The LSRA can focus specifically on these receptors and/or pathways. For example, a limited scope ERA can have a much narrower scope with respect to species and habitats examined than in the usual ERA.
• Toxicity/Hazard Assessment should identify and justify the toxicity data most appropriate to use for the receptor type or pathway that is the subject of the LSRA. If the LSRA is limited on the basis of a sensitive transport pathway only, the toxicity data used by the ministry in the development of the site condition standards may be used without further justification.
• Exposure Assessment should identify and justify the most appropriate exposure model to use for any special receptor type and/or pathway that is the subject of the LSRA. Quantitative exposure assessment is required only for the receptor type and/or pathway that is the subject of the LSRA.
• Risk Characterization is required only for the receptor type and/or pathway which is the subject of the LSRA. It may, for example, comprise a qualitative justification for applying the full depth generic site condition standard as an appropriate property specific standard for the receptor type and/or pathway which is the subject of the LSRA.

The three types of LSRA approaches may be used individually or in combination. Plans and justification for undertaking a LSRA should be explained in detail with the PSF for ministry comment on the proposed approach and suggested timeline for review. Additional guidance for each type of LSRA approach is provided in the following sections.

7.1.1 Source of Exceedance of Groundwater Standard is Located Off Property

The first type of LSRA approach is one in which one or more applicable site condition standards are exceeded in the groundwater under the property, but the source of the contamination was or is upgradient off-site (flow-through of contaminated groundwater). To qualify as a limited scope risk assessment the report should include verification that 1) there are no on-site sources of groundwater contamination (based on the Phase two ESA findings) and 2) soil concentrations on the property will cause no significant risk either to human health, via direct contact or the soil to indoor air pathway, or to terrestrial ecological receptors.

Quantitative risk assessment then may be limited to on-site receptors who may be exposed to the contaminated groundwater directly or through vapour migration.

7.1.2 Use of Full Depth Generic Site Condition Standards When Section 41 of the RSC Regulation Applies to the Property (Environmentally Sensitive Areas)

For some properties, there may be site conditions or characteristics which are very different from the conditions and assumptions used in developing the generic site conditions standards. Also, the generic site condition standards were developed to protect typical ecological receptors. There may be unique, highly sensitive ecological receptors at or in the vicinity of a site which were not considered in the development of the generic standards. Consultation with the appropriate agency (for example local ministry of Natural Resources and Forestry (MNRF) office, conservation authority, or local municipality) should be undertaken to determine if more protective ecological criteria are warranted.

Section 41 of the RSC Regulation lists situations where the applicable full depth generic potable site condition standard may not be protective. In such cases the applicable site condition standard is the full depth background site condition standard or a standard specified in a risk assessment. Alternatively, a limited scope risk assessment may be undertaken to address that particular site condition or sensitive receptor to determine if in fact they would be protected by the full depth generic site condition standard and, if so, propose the full depth generic site specific standard as the property specific standard for that site.

7.1.3 Modified Generic Risk Assessment

The third type of LSRA approach is a modified generic risk assessment, which may be used when only a small number of risk assessment assumptions differ from the generic assumptions and processes described in the Rationale for Development and Application of Generic Criteria for Use at Contaminated Sites in Ontario, 1996 (the Rationale document).

In order to be considered a modified generic risk assessment, the following conditions should be met:

• The proposed property specific standard is derived from the component values for the applicable soil type set out in tables A.2.1 to A.2.8 in Appendix A.2 of the Rationale document, and
• Any derivation of modified component values is limited to modification of soil properties used in the generic transport equations described in Appendix B.1.1 to B.1.11 in the Rationale document.

In conducting a modified generic risk assessment, the following alternative procedures should apply in following the procedures set out in Schedule C, Part I "Mandatory Procedures" and Table 1 of the RSC Regulation:

• The Problem Formulation elements of the HHRA and ERA should refer to all human and ecological pathways, respectively, and the associated component values set out for the applicable soil type in the Rationale document.
• The Toxicity Assessment/Hazard Identification elements of the HHRA and ERA may be limited to confirming the applicability of toxicity data set out in Appendix B.5.3.1 of the Rationale document to the receptors on the property.
• The Exposure Assessment elements of the HHRA and ERA may be limited to justifying the exclusion of any pathways set out in the component value tables and justifying the use of the remaining values. If any component values are modified, the exposure assessment in the modified generic risk assessment should justify the property-specific data used and follow quantitative risk assessment procedures set out in Schedule C of the RSC Regulation for all pathways.
• The Risk Characterization elements of the HHRA and ERA in the modified generic risk assessment may comprise a qualitative description of proposed property specific standards derived directly from the component value tables set out in the Rationale document and quantitative analysis for any proposed property specific standards derived by modification of the generic transport equations. Risk characterization would include selection of the lowest applicable value from the component value tables, according to the pathways identified as applicable in the exposure assessment, and checking those values against background (Table 1) values and detection limits according to the generic procedures set out in the Rationale document.

If the Rationale document does not provide an ecological or human health component value in the component value summary tables, the possible effects of the proposed modification on the receptors relevant to the missing component or pathway should also be evaluated. This evaluation can be conducted through the use of property specific data, reference to scientific literature and/or modelling. When modification of the components has been completed, all modified and unmodified components must be compared, and the most sensitive (lowest) value taken as the proposed property-specific standard.

Quantification of the HHRA elements of the risk assessment are not necessary for a COC, if site condition standards are based on ecological effects and if the concentrations on the property do not exceed the generic human health component value. Likewise, quantification of the ERA elements of the risk assessment is not necessary if the site condition standards are based on health effects and if the concentrations on the property do not exceed the generic ecological component values.

7.2 Estimation of Natural Local Background Concentrations

Conditions which the RSC Regulation states must be met for the estimation of natural local background concentrations as an alternative risk assessment approach are provided in Schedule C, Part II Section 8 of the RSC Regulation and are reproduced in the text boxes below:

If the situation allows for the use of estimation of natural local background concentrations as a risk assessment approach (NLBRA), a property owner may propose a natural local background concentration soil standard for a COC by undertaking a soil sampling and analysis program in accordance with Subsections 8(4) to (8) of Schedule C of the RSC Regulation. The alternative procedures provided in the regulation and copied below must be used in conducting any NLBRA.

The sampling program is intended to collect information from at least 10 different geographical locations that have not been affected by local point sources of air or land pollution, by local roads or highways, or by other known sources of contamination. These locations may be in rural (agricultural property use) or urban (all other property uses) settings in Ontario. Suitable sites include parks, cemeteries, forests, wood lots or large undeveloped tracks of land.

A sampling location is defined in section 48 of the RSC Regulation and means an area of the property that does not have a radius larger than two metres. This is an area within which multiple samples may be collected and composited to create a single sample representative of that sampling location. A minimum of 30 such sampling locations must be sampled, resulting in at least 30 separate samples for individual analysis. Sampling and analysis must be replicated in 1 out of 10 sample locations, therefore resulting in at least a further 3 samples from the same 30 sample locations.

Sampling data is then used to develop a property specific standard through a statistical calculation of the 90^th percentile of the analytical results. If the analytical results show large variability that cannot be attributed to a contaminant source, increased replicate sampling (i.e., more than two replicate samples from 1 out of 10 sample locations), and averaging the analytical results from the replicate sampling may be used to establish the 90^th percentile.

Provision is made in the regulation for areas of known, widespread soil contamination, where it is not possible to avoid the influence of historical, industrial emissions to soil surfaces. The sampling program may still be undertaken if it is designed to determine the change in COC concentration as it varies with increased depth from the surface. The use of this approach must be justified, for example on the basis of regional history and geology. A sampling program that establishes the variation in COC contamination from the surface soil to the subsurface soil may better reflect the soil conditions of the area. This may be used to establish remediation targets that are consistent with the change in COC concentrations with depth.

The regulation also provides an alternative procedure for use if sufficient natural local background concentration data have already been collected as part of another program. This provision in Schedule C, Part II, Section 8 (9) is reproduced below.

Existing geological summary data may be provided to the ministry with the PSF for consideration by the Director for use in justifying property specific standards based on local background concentrations. The ministry publication entitled "Ontario Typical Range of Chemical Parameters in Soil, Vegetation, Moss Bags and Snow (MOE 1993)" provides additional guidance on sampling and analysis procedures which property owners may use when developing property specific standards based on local soil background concentrations.

7.3 New Science Risk Assessment

Situations may arise in which a QP_RA wishes to use risk assessment when no applicable site condition standard exists for a particular COC, or decides to use risk assessment data or techniques that have not previously been reviewed by the ministry or do not fit within the current policy framework. RAs that are considered 'new science' under the RSC Regulation will require additional time for review of the data or techniques. The ministry will confirm, through comment on the PSF, if the data or techniques proposed in the PSF have been previously reviewed or fall within current policy decisions and will advise of the requirement for an extended timeline for review.

Risk assessment is considered 'new science risk assessment' (NSRA) if the risk assessment satisfies one or more conditions as set out in Schedule C, Part II, Section 9 of the RSC Regulation and reproduced in the sections below.

If the situation allows for the use of a NSRA, then the following alternative procedures may be used in conducting that NSRA. The following sections provide guidance for the three types of NSRA approaches. These approaches may be used individually or in combination with other approaches.

7.3.1 No Site Condition Standard in the Soil, Ground Water and Sediment Standards for a COC

When a COC is identified during a Phase two ESA for which there is no full depth generic site condition standard, it may be that there was insufficient toxicity data on which to base a site condition standard at the time of ministry standards development. The RSC Regulation provides for the development of a property specific standard for these COC, at the discretion of the QP_ESA who will sign the RSC, to determine if concentrations of the COC on site will interfere with the property use.

Property owners may either: a) choose to develop a property specific standard through a complete risk assessment for both human health and the natural environment as described in the RSC Regulation under Schedule C Part I, "Mandatory Requirements", or b) adopt a standard from another credible agency.

If a standard is adopted from another credible agency, the risk assessment should include an evaluation of how the basis for the value selection by that agency fits the specific requirements of the property under evaluation. Requirements for credible agencies that develop toxicity standards are specified in Schedule C, Part II, Section 9 of the RSC Regulation and reproduced in the text box below.

This process is also available to the QP_RA if there is no ministry site condition standard but they are aware, for example through review of recent toxicity databases, that new toxicity data has been published and reviewed by credible agencies since the development of the site conditions standards in the RSC Regulation. Such new toxicity data should be considered within the risk assessment. If the QP_RA uses new toxicity data to develop new TRVs, the ministry may consider the risk assessment a NSRA.

Ministry comment on the approach to using new toxicity data can be obtained through identification of the approach in the PSF. If the proposed new toxicity data has already been reviewed internally by the ministry, but is not reflected in the site conditions standards in the regulation, the ministry will include comment on its policy with respect to the new toxicity data with comments on the PSF. If the ministry has already accepted the new toxicity data for the conditions specified in the conceptual site model, or if the TRVs come from sources specified in section 4.3.2 of this procedure document, the use of this data may not require a 22 week review timeline.

7.3.2 Use of Proprietary Models

The development of property specific standards often involves the use of commercially available contaminant/media transport as well as various types of exposure scenario models. These models are considered proprietary when they are not available free of charge in the public domain. Many of these computerized models and their underpinning algorithms and assumptions have undergone extensive testing and verification. Others have been developed as an outcome of limited research studies and have not been widely used or validated under a variety of property conditions.

The RSC Regulation provides for the use of proprietary models in the development of property specific standards provided they can be reviewed by the ministry to determined applicability for the proposed conceptual site model. When providing comment on the Pre-Submission Form, the ministry will identify if a proprietary model requires further review as part of a risk assessment. If the ministry has already accepted the use of the proprietary model for the conditions specified in the conceptual site model, the ministry response to the PSF may advise that the 22 week review timeline will not be required. Requirements for use of proprietary models in the development of property specific standards as part of an NSRA are specified in Schedule C, Part II, Section 9 of the RSC Regulation and reproduced below.

The following information should be provided in the RA report to support the selection and use of proprietary models in risk assessments submitted for review:

• An accurate description of the model (i.e., the computational approach to solving a question, not the computer program within which the model is found) and the version of the model (including date of release), as well as a description of any changes to customize the application. The description does not have to be a lengthy, detailed discussion; however, it should provide a clear and concise summary of what the model does, how it functions (the mathematical expressions incorporated in the model) and what its limitations are (i.e., when it is and is not appropriate to use the model).
• A list of assumptions used in the development of the model and a discussion of the validity of the assumptions for the property (including the effect invalid assumptions will have on model results). This is an essential component in defining the sensitivity and uncertainty associated with the model.
• A description of all input parameters, including default parameters, together with the respective units of measure. If all the necessary units and references are provided, a list of parameters in tabular form will suffice.
• A sensitivity analysis which maintains the parameters at set values while each one of the parameters is individually varied to include at least the low range and high range of possible values for that parameter. The input values and the results for the sensitivity analysis of each parameter should be reported. For models with large numbers of inputs, a detailed sensitivity analysis may be impractical. In this case, the QP_RA should provide an analysis of the various parameters that have been changed from default values, which includes a brief rationale relating these changes to conditions at or expected at the property, sensitivity of the model to these changes conducted as described above and the likely effect this will have in terms of uncertainty associated with the results and conclusions.
• For hydrogeological exposure pathways (for example, soil/ground water to indoor air), a validation of the model output should be provided, where possible, by using field results at the property, if the field data are representative of the property. Fate and transport models are frequently used to predict the likely current extent of contamination as well as to assess the behaviour of contaminants under potential future scenarios. When a fate/transport model is utilized in the RA to predict contaminant concentrations in soil or ground water, the predicted concentrations should be verified through field sampling wherever possible. For modelling that predicts indoor air concentrations, field sampling of both soil gas at basement depth and indoor air may be warranted. It is recognized that there are factors that can contribute to indoor air quality that may not be related to COCs in the ground water or soil.
• On request, provide the ministry with information used to generate the proprietary model inputs, including but not limited to field measurements/parameters and clear references to assumptions. Some computer software use public domain models in a proprietary package or interface. If a copy is requested by the ministry, such software must be provided to the ministry in a manner which will not breach any person’s copyright or other intellectual property right.

If proprietary models and any supporting documentation are considered confidential, such material should be clearly marked as confidential.

7.3.3 Probabilistic Models

Probabilistic or stochastic analytical methods, such as Monte Carlo or Latin-Hypercube sampling, use probability density functions in the development of property specific standards. These methods are useful in analyzing the variability and uncertainty in risk assessments, provided that the analysis is supported by adequate data and sufficient technical documentation.

The RSC Regulation provides for the use of probabilistic methods in the development of property specific standards. It requires, however, that probability density functions are applied only to the contaminant concentrations and transport and exposure assessment components of the risk assessment as specified in the RSC Regulation and reproduced in the text box below. Additional review time may be required for the ministry to determine if the use of the proposed probability density functions is appropriate in the context of the proposed conceptual site model. If the ministry has already accepted the proposed probabilistic approach for the conditions specified in the conceptual site model, the use of this approach may not require a 22 week review timeline.

Requirements for use of proprietary models in the development of property specific standards as part of an NSRA are specified in Schedule C, Part II, Section 9 of the RSC Regulation and reproduced below.

Probabilistic analysis may or may not support risk management decisions during a risk assessment with respect to the remediation of contaminated properties. The use of probabilistic methods may not reduce the uncertainty inherent in risk assessments. However, when properly conducted, the use of these methods can better illuminate the range of risk mitigation associated with various property management options.

In the conduct of human health risk assessments, application of the probabilistic method should be restricted to the exposure assessment, as the application of stochastic methods to the dose-response analysis is not considered acceptable practice at this time. A probabilistic approach should be sufficiently supported by data and should add value to the assessment.

7.4 Wider Area of Abatement Risk Assessment

Under Schedule C (Part II, Section 10) of the RSC Regulation a risk assessment is considered a 'wider area of abatement (WAA) risk assessment' (WAARA) if the ministry, upon review of the PSF, identifies a property as being located within a wider area of abatement based on off-site regional information and considering the potential for additional responsible parties and multiple affected parties. These risk assessments may require additional time for the involvement of district staff in the risk assessment review and for adequate consultation with the community and other interested parties.

RSC Regulation requirements for risk assessments conducted in wider areas of abatement are reproduced below.

The proponent is encouraged to consider public communication as early in the site assessment and redevelopment process as possible. In many cases the interest of a broader segment of the public is directly relevant to the decision to accept a risk assessment. The ministry has the opportunity to require the development and implementation of a public communication plan as part of the risk assessment process through identification of the property within a WAA.

Ministry District staff will review the potential for a property to be located within a WAA at the time of PSF submission, based on the property location and any previous history of ministry orders and involvement in the area, off-site regional information and other risk assessments undertaken on the area. Contamination issues that may potentially involve off-site receptors may require the involvement of a wider scope of stakeholders.

If additional issues are identified at the time of reviewing the RA report, the Director will advise the property owner that the risk assessment is in a WAA through a notice issued under subsection 46(2) of the RSC Regulation.

Planning for public communication is a benefit to the proponent as it should reduce the likelihood of delays due to public opposition. Public communication provides the proponent the opportunity to gain the support of key stakeholders by;

• ensuring the affected stakeholders understand the process for site assessment, redevelopment and ministry approval,
• providing an opportunity for engagement of the public with clear rules and expectations for process and timing and,
• addressing stakeholder concerns before plans are finalized.

Where multiple properties are affected, public communication may lead to agreement or acceptance of a single risk assessment process or standard. Where multiple sources of contamination are present, public communication may lead to negotiation of joint remedial action.

Where the ministry has identified the property to be within a WAA, public communication required by the regulation should be at a level and of a type determined upon consultation with ministry staff. Communication with District staff may begin before submission of the PSF and a proposed communication plan may be provided with the PSF for ministry comment.

The WAARA report must include documentation of the plan for communication with the ministry and the public and the outcome of the communication plan as specified in the RSC Regulation. This should include a copy of any written public input.

Reporting requirements for the public communication plan are described in the RSC Regulation;

• Schedule C Table 1
  • Report Section 8 Public Comminucation Plan

Additional guidance is provided in Section 1.4.2 in this procedure document.

Section 8. Risk Assessment Submission and Review Process

8.1 Review Process

The review process followed for all risk assessment approaches is as follows:

• pre-consultation by way of the PSF, filled out by the QP_RA, signed by the QP_RA and the property owner and submitted to the ministry for comment;
• submission of the RA report to the ministry: The ministry will advise as early as possible in the review if more information is needed before a decision can be made. If this happens, as described in section 2 of this procedure document, proponents will have the opportunity to provide additional information in an advised limited period of time, re-submit the RA, withdraw the submission or have the risk assessment rejected. The basis for rejection will be provided by letter in all circumstances; and
• review of the RA report by the ministry and a notice from the Director to the owner of the property indicating either acceptance or non-acceptance of the risk assessment: A period of time is prescribed in the RSC Regulation for the review of the RA report submitted by the owner of the property to the Director.

8.2 Steps in the Risk Assessment Preparation and Review Process

When a property owner elects to use risk assessment to develop a property specific standard, the risk assessment will comprise three steps of a five step process to assess a property, develop standards and undertake remediation if necessary. All five steps are shown in flow chart form set out in Figure 1, and are briefly described below, to assist understanding of how risk assessment fits into the overall five step process under the RSC Regulation.

Other regulatory and compliance tools also may be required to address other aspects of redevelopment for many properties, including:

• disposal of excess soil,
• Minister’s approval for reuse of a former waste disposal site,
• potential for release of contaminants to the environment during remediation and construction,
• remedial activities which require Certificates of Approvals, and
• off site impacts.

8.2.1 Step 1 - Site Assessment

Prior to commencing a risk assessment, the owner of the property must retain a Qualified Person who can sign an RSC according to the RSC Regulation (QP_ESA) to carry out a Phase one ESA, and if necessary, a Phase two ESA. If the results of these assessments indicate the property does not meet the applicable site condition standards, the owner may choose to remediate the property to one of the applicable site condition standards or to use a risk assessment approach to develop property-specific site condition standards. The following decision points are identified in Figure 1:

• If the decision is made to remediate the property to one of the applicable site conditions standards, the owner of the property would proceed directly to Step 5, Site Remediation and filing the RSC.
• If the decision is made to utilize the risk assessment approach, the owner of the property would proceed to Step 2, the Preparation of Pre-Submission Form.

8.2.2 Step 2 - Preparation of Pre-Submission Form

In this step, the owner must retain a person qualified according to the RSC Regulation to undertake risk assessment (QP_RA) to evaluate the information obtained in Step 1 and develop a plan to undertake risk assessment on the owner’s behalf.

Based on the results of the Phase one ESA and the Phase two ESA, the QP_RA must organize a team of qualified specialists, as described in Section 1.3 of this Procedures document, to develop a conceptual site model which illustrates the condition of the site, the strength of the information available to support the risk assessment and the risks to be assessed. The QP_RA will prepare a PSF using the form provided on the ministry’s Brownfields webpage, attach site diagrams and QP_RA qualifications as specified in the RSC Regulation as well as any other relevant information. The property owner and QP_RA must sign the PSF and the property owner must submit the package to the ministry.

Submission of a PSF is a consultation process with the ministry. There is no approval involved. The purpose of the PSF is to provide the owner of the property with the opportunity to obtain ministry comment at the planning stage of the risk assessment approach.

The ministry will provide general comments to assist the owner in deciding if and how to proceed with the risk assessment. The comments will include an indication of the risk assessment review timeline based on the information provided in the PSF.

The following additional activity may be included within Step 2 in Figure 1;

• If the ministry has identified the potential for the risk assessment outcome to have an impact on stakeholders other than the property owner, the ministry may identify the property to be within a wider area of abatement. If this is the case, a public communication plan must be implemented and reported on with the risk assessment.

The ministry’s general comments on the content of the PSF relate to the risk assessment approach only and should not be construed to be acceptance of the risk assessment work or report. The decision as to whether to accept or not accept a risk assessment will be made by the Director upon submission of a complete RA report.

8.2.3 Step 3 - Completion of Risk Assessment

This step may begin before the ministry comment on the PSF is received by the property owner. In this step, the owner of the RA property may authorize the QP_ESA or QP_RA to undertake any additional site assessment/characterization as identified in the PSF and to consider any comments provided by the ministry. The QP_RA will then proceed with the risk assessment in accordance with the RSC Regulation, this Procedure document and using the approach and conceptual site model identified in the PSF, together with any comments received from the ministry in Step 2.

On completion of the risk assessment work, the owner of the RA property will submit the RA report to the Director for review. If the QP_RA elects to modify the RA approach from that described in the PSF, such modifications must be clearly identified in the RA report, as required in Schedule C Table 1 of the RSC Regulation. This requirement is for the purpose of expediting the RA review process.

The following additional activity may be included within Step 3 in Figure 1;

• If the RA proposes public communication, or is required to include public communication because the ministry has determined that the property lies within a wider area of abatement under the RSC Regulation, the QP_RA must conduct communication / consultation as part of the risk assessment process and include in the risk assessment report a summary of public comment and how the comments were considered in the risk assessment.

If the RA proposes risk management measures, the property owner should submit, with the RA report, a separate brief description of the risk management measures. The Director may publicly advise, by posting the description on the EBR that they are considering a CPU containing the risk management measure.

8.2.4 Step 4 - Acceptance / Non-Acceptance of Risk Assessment

On receiving the completed RA report, the ministry will assign the reviewer of the PSF to review the risk assessment. The time prescribed by the RSC Regulation for the risk assessment review will not begin until all the risk assessment components listed in the RSC Regulation have been received by the Director. Circumstances affecting the review timeline are in section 46, subsections (2)-(5) of the RSC Regulation and are reproduced below.

Due to the above-noted circumstances, the Director can request either

• an entire resubmission of the risk assessment (review timeline reset to the beginning) or
• submission of additional information by a specified date (timeline paused and restarting when the requested information is provided).

On completion of the review, the ministry reviewer will return their comments and recommendations to the Director. The Director will provide notice to the owner of the RA property in accordance with Section 168.5 of the EPA as to whether the RA is: 1) accepted, 2) accepted with issue of a CPU or 3) not accepted.

The following additional activities also may be included in Step 4 in Figure 1;

• If the RA proposes risk management measures, the ministry must publicly advise, by posting a description of the risk management measures on the EBR, that they are considering a CPU containing the risk management measures.
• If the Director becomes aware of one of the circumstances identified above the Director may request additional information as a revision loop within the RA review process timeline

The following decision points are included in Step 4 in Figure 1;

• If the Director does not accept the risk assessment the RA property owner may choose to revise the risk assessment. In this case the QP_RA may revise the risk assessment work and/or report as applicable and resubmit the RA report to the ministry as a new RA starting at Step 2 with a new PSF.
• If the owner of the RA Property chooses not to revise the risk assessment, the owner may remediate the property to the applicable site condition standard proceeding with Step 5. The owner may also choose not to remediate, provided they are not otherwise obligated to remediate, and forgo the benefits that come with the filing of a RSC.

There is an opportunity for both major and minor modifications to the RA report within the review process, prior to the Director’s decision. The decision to reject a risk assessment is likely to be based on a significant failing to respond to ministry concerns regarding the scope or approach to the risk assessment and the proposed property-specific standards. Repeating the PSF process provides the QP_RA and the property owner with the opportunity to rescope and revise the risk assessment approach.

8.2.5 Step 5 - Site Remediation and filing the RSC

After acceptance of the risk assessment by the Director and if remediation is required to meet the property specific standards set out in the RA report, the owner of the RA property would retain the QP_ESA to undertake the remediation and/or verification sampling. On completion of the remediation, a remedial report should be prepared that, together with the RA report would form the basis for completion of a RSC. If no remedial work is required, the Phase two ESA, together with the RA report would serve as the basis for completion of a RSC. The RSC may then be filed on the Brownfields Environmental Site Registry for acknowledgement by the ministry.

Figure 1: Flowchart for the Site Remediation Process with Risk Assessment

Download printer-friendly flowchart

Step 1 - Site Assessment

1. Owner retains QP_ESA to complete Phase One and Phase Two assessments as required.
2. Owner and QP_ESA decide whether to pursue generic or risk assessment option.
3. Will risk assessment approach be used?
   • If

     no

     , follow Regulation process to complete documentation.
   • If

     yes

     , proceed to step 2.

Step 2 - Risk Assessment: Preparation of Pre-Submission Form

1. Owner and QP_RA prepares PSF and submit to MOECC.
2. MOECC reviews and forwards to the owner comments on the content of the PSF, timeline for review requirement for public consultation may be identified.

Step 3 - Risk Assessment: Preparation of Risk Assessment Report

1. Public communication/consultation is completed by owner and QP_RA.
2. RA is conducted by QP_RA.
3. Owner sends completed RA to MOECC.

Step 4 - Risk Assessment: Approval Process

1. MOECC reviews RA. May request additional submissions with impact on timeline.
   • If required, proponent provides requested information/revisions to MOECC.
2. Risk management measures, if any are proposed, are posted on the EBR for public comment.
3. The director decides on the appropriate course of action.
   • Accepted: Proceed to Step 5.
   • Accepted with CPU.
   • Not accepted: Owner chooses to reverse RA.
     • If

       yes

       , repeat Step 2.
     • If

       no

       , follow Regulation process to complete documentation.

Step 5 - Site Remediation

1. Owner completes site remediation and verification in accordance with Regulation process.
2. RSC is electronically completed via Environmental Site Registry.
3. MOECC acknowledges RSC.

Section 9. Publications on Human Health Risk Assessment and Ecological Risk Assessment

9.1 Useful References for Human Health Risk Assessment

For additional information the reader can refer to both the Massachusetts "Background Documentation for the Development of the MCP Numerical Standards", which is contained within the Appendices of the ministry document "Rationale for the Development and Application of Generic Soil, Ground Water and Sediment Criteria for Use at Contaminated Sites in Ontario" (MOE, 1996b) and the United States Environmental Protection Agency document titled "Risk Assessment Guidance for Superfund, Volume I: Human Health Evaluation Manual (Part A)" (US EPA, 1989b) for more detailed guidance on conducting human health risk assessment.

A list of other useful resource literature on various aspects of human health risk assessment is provided in this section. This is not meant to be exhaustive and does not represent endorsement by the ministry. These documents also contain specific jurisdictional policies and default values which may not be applicable to Ontario. Sound scientific judgment should be exercised in utilizing any of the documents.

Angus Environmental Ltd. 1991. Review and Evaluation of Receptor Characteristics for Multi-media Assessments. Final Report. Prepared for Ministry of National Health and Welfare, Environmental Health Directorate, Ottawa.

Burmaster, D.E. and P.D. Anderson. 1994. Principles of good practice for the use of Monte Carlo Techniques in Human Health and Ecological risk assessments. Risk Analysis. 14: 477-481.

Canadian Council of Ministers of Environment (CCME). 1996. A Protocol for the Derivation of Environmental and Human Health Soil Quality Guidelines. Subcommittee of the CCME on Environmental Quality Criteria for Contaminated Sites. CCME, Winnipeg, Manitoba.

CAPCOA. 1993. Air Toxics "Hot Spots" Program. Revised 1992 Risk Assessment Guidelines. Toxics Committee of the California Air Pollution Control Officers Association, California. A Framework for Ecological Risk Assessment: General Guidance.

CCME. April, 1996 (c/o Manitoba Statutory Publications, 200 Vaughn St. Winnipeg, Manitoba, R3C-1T5, phone 204-945-4664). A Technical Appendix to this document is also available from Health & Welfare Canada. 1990. Health Risk Determination: The Challenge of Protection. Ministry of National Health and Welfare, Health Protection Branch, Canada.

Health Canada. 1994a. Canadian Environmental Protection Act. Human Health Risk Assessment for Priority Substances. Environmental Health Directorate, Ottawa, Canada.

Health Canada. 1994b. Human Health Risk Assessment of Contaminants from Contaminated Sites. Volume 1. Risk Assessment Guidance Manual. Draft. Environmental Health Directorate, Ottawa, Canada.

Health Canada. 1994c. Human Health Risk Assessment of Contaminants from Contaminated Sites. Volume 2. Risk Assessment Application Manual. Draft. Health and Welfare Canada, Environmental Health Directorate, Ottawa, Canada.

Health Canada. 1995. Investigating Human Health Exposure to Contaminants in the Environment: A handbook for exposure calculations. Health Canada, Ottawa, Canada, Cat. No. H49-96/1-1995E.

MDEP. April, 1994. Background Documentation for the Development of the MPC Numerical Standards. Massachusetts Department of Environmental Protection, Bureau of Waste Site Clean-up and Office of Research and Standards.

MOE. 1996a. Guidance on Sampling and Analytical Methods for Use at Contaminated Sites in Ontario. (Marsh, M., R. Lall, S. Capstick, A. Lewis, E. Pastorek and A. Kuja) Ontario Ministry of the Environment, Standards Development Branch. December, 1996.

MOE. 1996b. Rationale for the Development and Application of Generic Soil, Ground Water and Sediment Criteria for Use at Contaminated Sites in Ontario. (Kuja, A. and R. Pearson) Ontario Ministry of the Environment, Standards Development Branch. December, 1996.

MOE. 2005. Guidance on Oral Bioavailability Adjustments in Human Health Risk Assessment. Standards Development Branch, Position Paper. Final draft Sept 2005.

National Research Council (U.S.). 1983. Risk Assessment in the Federal Government: Managing the Process. National Academy Press, Washington, D.C.

National Research Council (U.S.). 1993. Issues in Risk Assessment. National Academy Press, Washington, D.C.

National Research Council (U.S.). 1994. Science and Judgment in Risk Assessment. National Academy Press, Washington, D.C.

Quebec Ministry of the Environment. 1991. Guidelines for Toxicological Risk Assessment: Summary and Supporting Documents. Preliminary. Risk Assessment Service, Montreal.

Richardson, G.M. 1997. Compendium of Canadian Human Exposure Factors for Risk Assessment. O'Connor and Associates Environmental Inc., Ottawa, Ontario.

US Environmental Protection Agency. 1986a. Guidelines for Mutagenicity Risk Assessment. Federal Register. Vol. 51, No. 185, September 24, pp. 34006-34012.

US Environmental Protection Agency. 1986b. Guidelines for the Health Risk Assessment of Contaminant Mixtures. Risk Assessment Forum, US EPA, Washington, DC, EPA/630/ R-98/002.

US Environmental Protection Agency. 1986c. Guidelines for Carcinogen Risk Assessment. Federal Register. Vol. 51, No. 185, September 24, pp. 33992-34003.

US Environmental Protection Agency. 1988. Superfund Exposure Assessment Manual. Office of Remedial Response, Washington, DC EPA/540/1-88/001.

US Environmental Protection Agency. 1989. Risk Assessment Guidance for Superfund. Volume I: Human Health Evaluation Manual (Part A); Interim Final. Office of Emergency and Remedial Response, US EPA, Washington, DC EPA/540/1-89/002.

US Environmental Protection Agency. 1991a. Guidelines for Developmental Toxicity Risk Assessment. Federal Register. Vol. 56, No. 234, December 5, pp. 63798-63828.

US Environmental Protection Agency. 1991b. Risk Assessment Guidance for Superfund. Volume I: Human Health Evaluation Manual (Part B): Development of Risk-based Preliminary Remediation Goals; Interim. Office of Emergency and Remedial Response, Washington, DC Publication 9285.7-01B.

US Environmental Protection Agency. 1991c. Risk Assessment Guidance for Superfund. Volume I: Human Health Evaluation Manual (Part C): Risk Evaluation of Remedial Alternatives; Interim. Office of Emergency and Remedial Response, Washington, DC Publication 9285.7-01C.

US Environmental Protection Agency. 1991d. Risk Assessment Guidance for Superfund. Volume I: Human Health Evaluation Manual, Supplemental Guidance, Standard Default Exposure Factors. Office of Emergency and Remedial Response, Washington, DC.

US Environmental Protection Agency. 1992a. Dermal Exposure Assessment: Principles and Applications. Interim Report. Office of Health and Environmental Assessment, Exposure Assessment Group, Washington, DC EPA/600/8-91/011B.

US Environmental Protection Agency. 1992b. Guidelines for Exposure Assessment. Federal Register. Vol. 57, May 29, pp. 22888-22938.

US Environmental Protection Agency. 1994. Draft Revisions to Guidelines for Carcinogenic-Risk Assessment. Contaminant Regulation Reporter. August 12, pp. 556-600.

US Environmental Protection Agency. 1994. Methods for Development of Inhalation Reference Doses. Environmental Criteria and Assessment Office, Office of Health and Environmental Assessment, US EPA, research Triangle Park, N.C.

US Environmental Protection Agency. 1996. Proposed Guidelines for Carcinogen Risk Assessment. Office of Research and Development, US EPA, Washington, DC, EPA/600/P-92/003C.

US Environmental Protection Agency. 1996. Reproductive Toxicity Risk Assessment, Federal Register 61(212):56274-56322.

US Environmental Protection Agency. 1998. Guidelines for Neurotoxicity Risk Assessment, US EPA, Washington, DC, Federal Register 63(93): 26926-26954.

US Environmental Protection Agency. 2000. Supplemental Guidance for Conducting Health Risk Assessment of Chemical Mixtures. Risk Assessment Forum, US EPA, Washington, DC, EPA/630/R-00/002.

US Environmental Protection Agency. 2002 Integrated Risk Information System (IRIS). National Centre for Environmental Assessment, US EPA, Washington, DC.

9.2 Useful References for Conducting ERAs

A list of other useful resource literature on various aspects of ecological health risk assessment is provided in this section. This is not meant to be exhaustive and does not represent endorsement by Ministry. These documents also contain specific jurisdictional policies and default values which may not be applicable to Ontario. Sound scientific judgment should be exercised in utilizing any of the documents.

Bartell, S.M., R.H. Gardner, and R.V. O'Neill. 1992. Ecological Risk Estimation. Lewis Publishers, Ann Arbor, Michigan.

BC MELP. 1998. Protocol for Contaminated Sites, Guidance and Checklist for Tier 1 Ecological Risk Assessment of Contaminated Sites in British Columbia. British Columbia Ministry of Environment, Lands and Parks.

BJC (Bechtel Jacobs Company). 1998a. Empirical models for the uptake of inorganic chemicals from soil by plants. BJC/OR-133. Oak Ridge, TN.

BJC (Bechtel Jacobs Company). 1998b. Biota Sediment Accumulation Factors for Invertebrates: Review and Recommendations for the Oak Ridge Reservation. BJC/OR-112. Oak Ridge, TN.

Buchman, M. 1992. How to Design an Ecological Risk Assessment. in HMC/Superfund '92 Proceedings, Hazardous Materials Control Resources Institute, Maryland.

CCME. 1996. A Framework for Ecological Risk Assessment at Contaminated Sites: General Guidance, CCME Subcommittee on Environmental Quality Criteria for Contaminated Sites, March, 1996. Available c/o Manitoba Statutory Publications 200 Vaughn St., Winnipeg, Man., R3C-1T5.

CCME. 1997. A Framework for Ecological Risk Assessment: Technical Appendices, CCME Subcommittee on Environmental Quality Criteria for Contaminated Sites. March, 1997. Winnipeg, Man..

Chapman, P.M. and Anderson, J. 2005. A Decision-Making Framework for Sediment Contamination Integrated Environmental Assessment and Management Vol ,1, No.3, pp. 163-173. SETAC 2005.

Efroymson, R.A., M.E. Will, G.W. Suter II and A.C. Wooten. 1997a. Toxicological benchmarks for screening potential contaminants of concern for effects on terrestrial plants: 1997 revision. ES/ER/TM-85/R3. Oak Ridge National Laboratory, Oak Ridge, TN.

Efroymson, R.A., M.E. Will, and G.W. Suter II. 1997b. Toxicological benchmarks for screening potential contaminants of concern for effects on soil and litter invertebrates and microbial processes: 1997 revision. ES/ER/TM-126/R2. Oak Ridge National Laboratory, Oak Ridge, TN.

Ford, K.L., F.M. Applehans, and R. Ober. 1992. Development of Toxicity Reference Values for Terrestrial Wildlife. in HMC/Superfund '92 Proceedings. Hazardous Materials Control Resources Institute, Maryland.

Freshman J.S. and Menzie C.A. 1996. Two wildlife exposure models to assess impacts at the individual and population levels and the efficacy of remedial actions. HERA: Vol. 2, No. 3, pp. 481-498.

Mayernick, J.A. and K. Fehrenkamp. 1992. A New Model for Conducting Quantitative Ecological Risk Assessments at Hazardous Waste Sites. in HMC/Superfund '92 Proceedings, Hazardous Materials Control Resources Institute, Maryland.

Menzie et al. 2000. An Approach for Incorporating Information on Chemical Availability in Soils into Risk Assessment and Risk-based Decision Making. Human and Ecological Risk Assessment. Vol 6, No 3, pp 479-510.

Nagy, KA. 2001. Food requirements of wild animals: Predictive equations for free-living mammals, reptiles and birds. Nutrition Abstracts and Reviews. Series B Livestock Feeds and Feeding. 71(10):21R-31R.

Sample, B.E., Opresko, D.M. and Suter II, G.W. 1996. Toxicological Benchmarks for Wildlife: 1996 Revision. ES/ER/TM-86/R3. Oak Ridge National Laboratory, Oak Ridge, TN.

Sample, B.E., Aplin, M.S., Efroymson, R.A., Suter II, G.W. and Welsh, C.J.E. 1997. Methods and tools for estimation of the exposure of terrestrial wildlife to contaminants. ORNL/TM-13391. Oak Ridge National Laboratory, Oak Ridge, TN.

Sample, B.E., Beauchamp, J.J., Efroymson, R.A., Suter II, G.W. and Ashwood, T.L. 1998a. Development and validation of bioaccumulation models for earthworms. ES/ER/TM-220. Oak Ridge National Laboratory, Oak Ridge, TN

Sample, B.E., Beauchamp, J.J., Efroymson, R.A. and Suter II, G.W. 1998b. Development and validation of bioaccumulation models for small mammals. ES/ER/TM-219. Oak Ridge National Laboratory, Oak Ridge, TN

Suter, G.W. 1993. Ecological Risk Assessment, Lewis Publishers, Chelsea, Michigan.

Suter, G.W., Efroymson, R.A., Sample, B.E., and Jones, D.S. 2000. Ecological Risk Assessment for Contaminated Sites. Lewis Publishers, CRC Press LLC.

US Environmental Protection Agency. 1989a. Ecological Assessment of Hazardous Waste Sites: a Field and Laboratory Reference. Warren-Hicks, W., B.R. Parkhurst and S.S. Baker, (eds). EPA/600/3-89/013. Prepared by Kilkelly Environmental Associates for USEPA.

US Environmental Protection Agency 1993. Wildlife Exposure Factors Handbook. Volume I. EPA/600/R-93/187a. Office of Research and Development, Washington, DC.

US Environmental Protection Agency. 1998. Guidelines for Ecological Risk Assessment. EPA/630/R-95/002F. April 1998. Risk Assessment Forum, Washington, DC.

US Environmental Protection Agency Ecological Soil Screening Levels

US Geological Survey, Columbia Environmental Research Centre website

U.S. Navy. 2003. US Ecological Screening and COPC Refinement for Sediment, Soil, and Surface Water.

Appendix A

MOECC Human Health Based Toxicity Values

Currently, there are certain contaminants for which the Ministry has developed health based toxicity values. These values should be used in preference to values from any other jurisdictions.

Dioxins and Furans

Tolerable Daily Intake (TDI) for 2,3,7,8-TCDD or its toxicity equivalent (TEQ)
= 10 pg TEQ kg⁻¹ body weight day ⁻¹

Although the recommended TDI is developed based on the effects of 2,3,7,8-TCDD, it is possible to calculate tolerable levels of exposure for all dioxins and furans. This is done by taking the concentrations of the 17 most toxic dioxins and furans and 12 congeners of TCDD-like PCBs, multiplying each one by a toxic equivalency factor (TEF) - its toxicity relative to 2,3,7,8-TCDD - and adding up all the corrected concentrations expressed as 2,3,7,8-TCDD toxic equivalents. The World Health Organization (WHO) Toxicity Equivalency Factors (TEF) is provided in Table A-1 as outlined by the WHO.

Lead

Total intake of concern (IOC) = 1.85 µg kg⁻¹ body weight day⁻¹
for sensitive populations within the community

N-Nitrosodimethylamine (NDMA)

Cancer slope factor = 51 [mg/kg-day]⁻¹
For a lifetime exposure

WHO Toxic Equivalency Factors (TEFs) for human health risk assessment (TEFWHO-97)

Appendix B

Calculation of Weighted Average Chronic Daily Intake (CDI)

The weighted chronic daily intake (CDI) is the estimated daily intake averaged over a lifetime and adjusted for body weight. This is useful, especially in the case of carcinogens, for which the dose response relationship is usually developed based on chronic exposure throughout a receptor’s lifetime. In situations where the level of exposure of an individual to a given contaminant differs vastly during the course of his/her lifetime, either due to differing environmental levels, body weight or behaviour, calculating the weighted chronic daily intake of the individual allows comparison of the individual’s exposure against the health based toxicity values on a common basis.

In general, the equation for calculating the weighted average chronic daily intake (CDI) is expressed as follows:

n = µ (Daily intake i × years i) ⁄ (body weight i × normal life span);

i = 1

n

chronic daily intake

where i

stage of an individual’s life

µ yeari

normal lifespan

Example:

Individuals experience a higher level of exposure during the first 7 years of his/her life per unit body weight.

The daily intake of the contaminant for children (1-7 years old) is 1.6 µg/day.

The daily intake of the contaminant for older children and adults (> 7 years old) is 0.4 µg/day.

Assuming the normal lifespan to be 70 years, the average body weight of the child (1-7 years) to be 15 kg and the average body weight of older children and adults to be 70 kg, the weighted average chronic daily intake (CDI) can be calculated as follows.

CDI = intake (child) × 7 yr + intake (adult) × 63 yr

15 kg × 70 yr

70 kg × 70 yr

= 1.6 µg/day × 7 yr + 0.4 µg/day × 63 yr

15 kg × 70 yr

70 kg × 70 yr

= 0.016 µg/kg/day.