Workplace medical screening is clinical screening for workers with workplace exposure to hazards that may cause occupational disease. Screening may identify workers with unrecognized disease leading to earlier diagnosis and management. Screening data may also add surveillance information at the workplace and broader provincial levels.

Currently in Ontario, there are legally mandated medical screening requirements for workers exposed to some designated substances. Some workplaces may employ screening for exposures beyond the designated substances.

Designated substances in Ontario include: Acrylonitrile, arsenic, asbestos, benzene, coke oven emissions, ethylene oxide, isocyanates, lead, mercury, silica, and vinyl chloride. Medical screening is required for asbestos, benzene, coke oven emissions, isocyanates, lead, mercury and silica.


Ontario legislative and regulatory requirements

The Occupational Health and Safety Act (OHSA 26(h)), requires workplaces to “establish a medical surveillance program for the benefit of workers as prescribed.”

The designated substance regulations (Reg. 490/09) specify:

  • general screening requirements (27, 28, 29, 30, 31) for acrylonitrile, arsenic, ethylene oxide, vinyl chloride
  • codes for workplace medical surveillance for asbestos, benzene, coke oven emissions, isocyanates, lead (inorganic and organic), mercury (alkyl and non-alkyl compounds) and silica
  • Physicians conducting medical examinations and/or supervising clinical tests of a worker must be competent to do so because of knowledge, training and experience in occupational medicine. Physicians have a reporting obligation to the MLITSD if the worker is found to be fit with limitations or unfit. Healthcare providers may have a role in respirator programs.

Historic context

The Ministry of Labour used to perform medical screening/surveillance for silica and asbestos-exposed workers. This included a ministry-run van that travelled the province performing chest X-rays and spirometry for workers exposed to silica and asbestos. The results were held by the Ministry of Labour and have been used for research and claims adjudication. With the introduction of the designated substance regulations, the Ministry of Labour ended its program.

Current context

Employers are responsible for the provision and funding of the medical screening programs that are required under the designated substance regulations. Worker participation in medical screening programs is voluntary. Ministry inspectors may write orders to establish a medical screening/surveillance program if they inspect a workplace and find that such a program is not provided. A review of orders from 2017–2021 found 56 for medical screening/surveillance.

Consultation and review summary

Research highlights

Note: a comprehensive summary of research is provided on the CREOD website.

  1. Research from Ontario provides support for the use of screening for isocyanates. Following the introduction of the designated substance regulations, there was a decrease in occupational asthma claims related to isocyanates that were possibly linked to the introduction of the screening requirements.
  2. In addition to required screening, other ODs may benefit from screening. A tool has been developed and tested (either self-administered or administered by healthcare providers) to identify workers with early changes related to hand dermatitis.

Reports and reviews

A report commissioned by the Ministry of Labour in 2010 (Holness DL, House RA, Qureshi R, Saary MJ, Thompson A. Review of the medical surveillance codes for the designated substances. Ontario Ministry of Labour, June 2010).

This report examined the then-current evidence for screening for the designated substances and recommended appropriate screening tests for the various designated substances. It also cautioned that “a mechanism to provide for the evolving evidence with respect to both health effects and screening tests would be advantageous so program recommendations could be modified as new evidence is found.” Drs Rajaram and Holness wrote an article for the Ontario Medical Review to provide physicians with information about the changes being made (Rajaram N, Holness DL. Updates to Code for Medical Surveillance for Designated Substances to take effect January 1, 2020: physician who perform medical surveillance are advised to review upcoming changes. Ontario Medical Review, 2019;86:42–43.)

Stakeholder focus groups

Gaps themes

  1. Disease screening for DS is important, and opportunities to expand to other exposures exists.
  2. However, little is known about current workplace screening including screening methods, participation rates, and how results are shared and used.
  3. As a result, there is a general lack of trust in disease screening and surveillance.

Solutions themes

  1. Workplace screening data needs to be accessible, transparent and centralized to gain confidence in the program.
  2. Opportunities for workers to self-screen should be explored.

Summary review findings

  1. In the past, the MLITSD performed targeted surveillance (for example asbestos and silica) by conducting chest X-rays and spirometry through a ministry-run program, and this was deemed as helpful.
  2. The designated substance (DS) regulations contain provisions for workplace medical screening programs.
  3. There is currently no formal process for developing and updating the designated substance medical codes.
  4. There is currently no way of knowing what medical screening programs are implemented in Ontario, the results of the screening including for DSs.
  5. It is unclear who is conducting the medical surveillance programs and how — which physicians, qualifications of those providing services, quality assurance programs for various testing, such as pulmonary function testing — and whether physicians involved are aware of their reporting obligation to the MLITSD.
  6. Trust in screening practices is low including concerns about how data is being used/for what purpose.
  7. Medical screening data is currently not connected to the provincial surveillance system.


System goals

Improved clinical screening of workers exposed to designated substances and other exposures of concern is required in order to enhance:

  • early recognition of signs and symptoms of possible occupational disease
  • timely follow-up for definitive diagnosis including work-relatedness
  • identifying trends in the workplace
  • informing and prioritizing prevention efforts in the workplace
  • contributing real-time data to the provincial disease surveillance system and potential cluster identification

Short term recommendations

3.1 Assess the current state of workplace medical screening in Ontario by investigating what is actually being done for medical surveillance of designated substances as identified in the regulations

Implementation guidance:

  • Survey a sample of workplaces with designated substances (DS) to identify the presence of a program, how many workers are participating, if the JHSC is receiving reports, and what happens with the data and clinical follow-up
  • Survey a sample of physicians/HCPs providing medical screening services to assess their qualifications/training, what they are doing in terms of testing, how results are shared with the worker, and reporting to the JHSC and the MLITSD

3.2 Improve the review of requirements for medical codes for designated substances

Implementation guidance:

  • Strike an Expert Clinical Panel reporting to the Provincial Physician to develop an approach for Ontario that considers best practices in other jurisdictions and considers the context outlined in the survey results from recommendation 1 above.

Longer term recommendations

3.3 Develop a multi-pronged programmatic approach to medical screening for designated substances

Implementation guidance:

  • MLITSD uses current state assessment to inform the starting point for improvements in medical screening considering the role of government (monitoring, auditing), the role of workplaces (program delivery), role of workers (participation rights and benefits), and the role of clinicians (clinical services).
  • Align the effort with the development of the provincial disease surveillance system to ensure appropriate linkages.

3.4 Expand the screening activities for other emerging exposures of concern as identified through the provincial disease surveillance system

3.5 Implement simple self-screening tools for workers starting with lung and skin disease to improve early recognition (as noted in Topic 1)