Appendix

The Appendix is intended for use in conjunction with the 2023 Annual Air Quality in Ontario Report. The Appendix briefly describes the provincial Air Quality Health Index (AQHI) network, quality assurance and quality control procedures, and the Ministry of the Environment, Conservation and Parks’ air quality database. It also includes a series of tables displaying station locations and a listing of the summary statistics including means, maximums, percentile values and the number of exceedances of the Ontario Ambient Air Quality Criteria (AAQC) for each pollutant. In addition, trends for select common pollutants are displayed for a 10-year period, whereas trends for select research parameters are displayed for an 8-year period.

Monitoring network operations

Network description

In 2023, the ministry operated 38 ambient air monitoring sites across Ontario as part of the AQHI network. The AQHI network was comprised of 130 continuous monitoring instruments at 38 sites. These instruments have the capability of recording minute data (approximately 70 million data points per year) that are used to scan and validate the continuous hourly data.

Quality assurance and quality control

Day-to-day maintenance and support of the instruments are administered by ministry staff. Instrumentation precision is verified by daily automatic internal zero and span checks. Data analysts and station operators review span control charts to confirm instrument precision using a telemetry system. A quarterly quality assurance and quality control (QA/QC) review is performed on the ambient data set to highlight anomalies and administer corrective action in a timely manner.

The air monitoring station operators routinely inspect and maintain monitoring equipment and stations with mandatory quarterly on-site visits where secondary transfer standards are used to calibrate instrumentation. Station maintenance activities are recorded using Fieldworker Inc. software, an electronic documentation solution; this information is transferred directly to the ministry’s database. The instrumentation used throughout the provincial air monitoring network has been standardized to Thermo Electron Corporation analyzers to streamline parts inventory and leverage common hardware used within each analyzer. The following is a summary of the instrumentation deployed within the network and are all US EPA designated equivalent methods:

• Nitrogen Oxides – TE42C/I
• Fine Particulate Matter – T640 and SHARP 5030^{footnote 1[1]}
• Ozone – TE49C/I
• Sulphur Dioxide – TE43I
• Carbon Monoxide – TE48I
• Total Reduced Sulphur – TE43I/CDN101

The ministry operates a laboratory with gas reference standards that adhere to those of the U.S. National Institute of Standards and Technology (NIST) and the Air Quality Research Division of Environment and Climate Change Canada. The secondary transfer standards used by station operators are referenced and certified to the ministry’s NIST primary standards on a quarterly basis.

The TRAP instrumentation used throughout the roadside air monitoring network include:

• Ultrafine Particles – Teledyne API Model 651
• Black Carbon in PM_2.5 – Magee Scientific AE33 Aethalometer
• Heavy Metals in PM_2.5 – Cooper Environmental Xact 625
• Major Components in PM_2.5 – Aerodyne Quadrupole Aerosol Chemical Speciation Monitor (ACSM)

The Ontario ambient air quality monitoring network undergoes constant maintenance to ensure a high standard of quality control. Continuous real-time data are consistently reviewed, assessed, and validated by ministry staff. Immediate actions are taken to correct any inconsistencies that may affect the validity of the data. These measures ensure ambient air monitoring data are valid, complete, comparable, representative, and accurate. As a result, the 2023 ambient air quality monitoring network had 98.0% valid data from over one million hourly data points.

Data base

The ambient air quality data used in this report are stored in the ministry’s air quality information system (AQUIS) and are made available through the Air Quality Ontario web site, and the Ontario Data Catalogue. A statistical pattern test is used to identify data anomalies, such as unusual pollutant concentrations. Each pollutant has a predetermined concentration range based on historical data. Values outside this range are flagged for further investigation.

Data are obtained from automated ambient air monitoring instruments that operate continuously to produce an average measurement for every hour for a possible total of 8,760 measurements in a given year. Hourly parameters measured include NO/NO₂/NO_x, PM_2.5, O₃, SO₂, CO and TRS compounds. An annual mean requires at least 6,570 hourly readings. In addition, each quarter of the year should have 75% valid data for PM_2.5, whereas for ozone, only the 2^nd and 3^rd quarters of the year require 75% valid data based on protocols that are consistent with the Canadian Council of Ministers of the Environment (CCME) and the United States Environmental Protection Agency (U.S. EPA). For VOC samples, half of the method detection limit (MDL) is applied as appropriate to concentrations measured below the detection limit. An annual and/or monthly mean for 24-hour VOC samples requires 50% of valid samples. The 50% data requirement also applies to the research parameters (ultrafine particles, black carbon and trace metals and major components of PM_2.5).

Network descriptive table

The AQHI network for 2023 is summarized in the 2023 Ontario Continuous Ambient Air Monitoring Network. The table displays the station name, numerical identifier and pollutants measured. The numerical identifier is the station (ID) number, the first digit of which identifies the geographic region in which the station is located. Air monitoring stations within the AQHI network can measure up to six common pollutants (NO₂, PM_2.5, ozone, SO₂, CO and TRS compounds) based on the pollutant(s) of concern for the regional area it represents. The 2023 Ontario Continuous Ambient Air Monitoring Network also identifies the type of air monitoring site: ambient, roadside, Canadian Ambient Air Quality Standard (CAAQS), and/or National Air Pollution Surveillance (NAPS). Ambient sites represent the general air quality of an area without any direct influence of local industrial sources. Road-side sites are typically within approximately 100 m of a major roadway with daily traffic volumes greater than 10,000 vehicles per day.

Annual statistics and trends

The annual statistical data and trends for various continuous pollutants and selected volatile organic compounds are presented in the Appendix. The annual averages, maximums and percentiles are displayed in the annual statistics tables. (A percentile is the value equal to or below which a given percentage of the data set falls. For example, if 70% of the data are equal to or below 0.10 ppm, the 70^th percentile is 0.10 ppm).

The trends are calculated from monthly means through the Mann-Kendall (M-K) test. The M-K test is a nonparametric statistical approach that can be applied to data without making assumptions on the nature of the data distribution. The M-K test is essentially a test for uniform progression (zero change) in the slope of the linear regression of time-ordered data versus time (Gilbert, 1987). The M-K test is particularly suitable for environmental monitoring data since missing, trace and below detection limit values can be handled. This test can also be used to compare trends at multiple stations. The seasonal Kendall test, also performed in this Report, is a generalization of the M-K test (Gilbert, 1987) for use to determine the true trend when there are seasonal cycles in the data which do not constitute a true long-term trend. The change over time was based on the Sen’s slope, also known as the Thiel-Sen’s estimator of linear trend. The Sen’s slope is closely related to and applied in conjunction with the M-K Test. Compared to the common least squares regression, the Sen’s slope procedure is a nonparametric method for computing the value of the true slope when there are gross errors or outliers in the data without making assumptions of a normal distribution on the data (Gilbert, 1987).

Other informative tables

Calculated CAAQS metrics for PM_2.5, ozone, NO₂ and SO₂ are presented for 2023 (based on a three-year average, 2021-2023) and over a 10-year period in Canadian Ambient Air Quality Standard Reporting. The air zone management levels associated to each CAAQS reporting pollutant are also provided for reference. The percentage distribution of hourly AQHI readings within the various health risk categories for each of the 38 monitoring sites, and the number of air quality alerts issued in Ontario during 2023 are summarized in AQHI and Air Quality Alert Program Reporting.

2023 air monitoring network

Notes

ID

station identfication number

Year

year station began monitoring

Air intake

height of air intake above ground (m)

Type

type of monitoring site

A

ambient

RS

road-side

C

Canadian Ambient Air Quality Standard (CAAQS)

N

National Air Pollution Surveillance (NAPS)

AQHI

Air Quality Health Index

T

telemetry

NO₂

nitrogen dioxide

PM_2.5

fine particulate matter

O₃

ground-level ozone

SO₂

sulphur dioxide

CO

carbon monoxide

TRS

total reduced sulphur

Y

yes

Additional parameters measured at roadside air monitoring stations:

• Ultrafine particles - Toronto North, Toronto Hwy 401, and Toronto Island.
• Black carbon - Windsor Downtown, Windsor West, Hamilton Downtown, Toronto East, Toronto North, Etobicoke South, Toronto Hwy 401, and Toronto Island.
• Heavy metals in PM_2.5 - Windsor West, Hamilton Downtown, Toronto Hwy 401.
• Major components in PM_2.5 - Windsor West and Toronto Hwy 401.

2023 annual statistics

2023 nitric oxide (NO) annual statistics

Unit: parts per billion (ppb)

2023 nitrogen dioxide (NO₂) annual statistics

Unit: parts per billion (ppb)      
NO₂ 1h AAQC: 200 ppb          
NO₂ 24h AAQC: 100 ppb

2023 nitrogen oxides (NO_x) annual statistics

Unit: parts per billion (ppb)

2023 fine particulate matter (PM_2.5) annual statistics

Unit: micrograms per cubic metre (μg/m³)          
PM_2.5 24h Reference Level: 27 μg/m³          
PM_2.5 Annual Reference Level: 8.8 μg/m³

Notes

• The Teledyne Advanced Pollution Instrumentation (TAPI) Model T640 Particluate Matter (PM) Mass Monitor instrument was deployed across the Ontario ambient air quality network in 2023, however, due to unique circumstances, a subset of select stations (Toronto Downtown, Oshawa and Thunder Bay) had the install delayed. This subset continued PM_2.5 monitoring with the Synchronized Hybrid Ambient Real-time Particulate (SHARP) 5030 instrument in 2023. These two methods are considered equivalent and are comparable for analyses.
• Ontario uses the 24-hour PM_2.5 CAAQS “as is” for comparison to the 24-hour measurement of air quality data; this value is considered a Reference Level.
• Ontario uses the annual PM_2.5 CAAQS “as is” for comparison to a single annual average of air quality data; this value is considered a Reference Level.

2023 ozone (O₃) annual statistics

Unit: parts per billion (ppb)      
O₃ 1h AAQC: 80 ppb

2023 sulphur dioxide (SO₂) annual statistics

Unit: parts per billion (ppb)      
SO₂ 10 min AAQC: 67 ppb          
SO₂ 1h AAQC: 40 ppb          
SO₂ 1y AAQC: 4 ppb

2023 carbon monoxide (CO) annual statistics

Unit: parts per million (ppm)      
CO 1h AAQC: 30 ppm          
CO 8h AAQC: 13 ppm

Note

• INS indicates there was insufficient data to calculate a valid annual mean.

2023 total reduced sulphur (TRS) compounds annual statistics

Unit: parts per billion (ppb)

Note

• INS indicates there was insufficient data to calculate a valid annual mean.

2023 benzene annual statistics

Unit: micrograms per cubic metre (μg/m³)          
Benzene 24h AAQC: 2.3 μg/m³          
Benzene Annual AAQC: 0.45 μg/m³

Note

• INS indicates there was insufficient data to calculate a valid annual mean.

2023 toluene annual statistics

Unit: micrograms per cubic metre (μg/m³)          
Toluene 24h AAQC (based on odour): 2,000 μg/m

Note

• INS indicates there was insufficient data to calculate a valid annual mean.

2023 ethylbenzene annual statistics

Unit: micrograms per cubic metre (μg/m³)          
Ethylbenzene 24h AAQC: 1,000 μg/m³

Note

• INS indicates there was insufficient data to calculate a valid annual mean.

2023 m- and p-xylene annual statistics

Unit: micrograms per cubic metre (μg/m³)

Note

• INS indicates there was insufficient data to calculate a valid annual mean.

2023 o-xylene annual statistics

Unit: micrograms per cubic metre (μg/m³)

Note

• INS indicates there was insufficient data to calculate a valid annual mean.

2023 1,3-butadiene annual statistics

Unit: micrograms per cubic metre (μg/m³)          
1,3-Butadiene 24h AAQC: 10.0 μg/m³          
1,3-Butadiene Annual AAQC: 2.0 μg/m³

Note

• INS indicates there was insufficient data to calculate a valid annual mean.

10-year trends

10-year trend for nitric oxide (NO)

Annual mean (ppb)

Notes

• INS indicates there was insufficient data to calculate a valid annual mean.
• Station 14111 replaced station 14064 as the Sarnia site in 2016.
• Station 29214 replaced station 29114 as the Hamilton Mountain site in 2019.
• Station 34021 replaced station 34020 as the Toronto North site in 2017.
• Station 44029 was operated by the Halton Region prior to 2019.
• Station 45027 replaced station 45026 as the Oshawa site in 2018.
• Station 46090 replaced station 46089 as the Brampton site in 2017.
• N-SSS - Non-Significant Sen's Slope (significant trend not detected).

10-year trend for nitrogen dioxide (NO₂)

Annual mean (ppb)

Notes

• INS indicates there was insufficient data to calculate a valid annual mean.
• Station 14111 replaced station 14064 as the Sarnia site in 2016.
• Station 29214 replaced station 29114 as the Hamilton Mountain site in 2019.
• Station 34021 replaced station 34020 as the Toronto North site in 2017.
• Station 44029 was operated by the Halton Region prior to 2019.
• Station 45027 replaced station 45026 as the Oshawa site in 2018.
• Station 46090 replaced station 46089 as the Brampton site in 2017.
• N-SSS - Non-Significant Sen's Slope (significant trend not detected).

10-year trend for nitrogen oxides (NO_x)

Annual mean (ppb)

Notes

• INS indicates there was insufficient data to calculate a valid annual mean.
• Station 14111 replaced station 14064 as the Sarnia site in 2016.
• Station 29214 replaced station 29114 as the Hamilton Mountain site in 2019.
• Station 34021 replaced station 34020 as the Toronto North site in 2017.
• Station 44029 was operated by the Halton Region prior to 2019.
• Station 45027 replaced station 45026 as the Oshawa site in 2018.
• Station 46090 replaced station 46089 as the Brampton site in 2017.
• N-SSS - Non-Significant Sen's Slope (significant trend not detected).

10-year trend for fine particulate matter (PM_2.5)

Annual mean (µg/m³)