Top 5 changes you should know about Occupational Exposure Limits in Ontario

Wednesday, July 03, 2019

New limits become law Jan. 1, 2020

WSN health and safety specialist Dan Suess consults with client

Update Dec 2019: Occupational Health Regulatory Modernization Amendments posted by Ministry of Labour 

To better protect workers, the Ministry of Labour (MOL) is preparing new legislation under the Occupational Health and Safety Act to improve occupational exposure limits, respiratory protection, and air sampling. Expected to become law soon, it will be up to Ontario employers to ensure they’re operating within the limits set out by the MOL.  

Occupational exposure limits (OELs) restrict the amount and duration of worker exposure to hazardous workplace substances such as asbestos, benzene and lead, and public consultation is currently underway. 

“Some of these substances may appear in mixtures that our industrial clients use,” says Dan Suess, Health and Safety Specialist at Workplace Safety North (WSN), “so this is an excellent time to review your Safety Data Sheets to determine whether these components are contained within the chemicals in use at your facility or in your workplace.”

The distinction between the Workplace Hazardous Materials Information System (WHMIS) and new OELs is that WHMIS is an information system with labels, safety data sheets, and training that educate workers about hazardous substances, while OELs relate to sampling the air to make sure that workers aren’t exposed to hazardous levels of contaminants.

“They do go hand in hand,” says Jason Chevrier, WSN Industrial Hygiene-Mine Ventilation Specialist, “it’s just that they have different, separate functions. The WHMIS label will indicate products that are flammable or toxic, for example, but one component of industrial hygiene is testing the air so you can determine if the concentrations can harm people. The overall goal is to put appropriate controls in place to protect the worker.

“Let’s say you’re using a can of spray foam insulation to insulate the windows in your home, the WHMIS label will tell you the isocyanates in the foam are toxic and the material is flammable, but to determine how much isocyanates you’re exposed to, you’d have to sample the air and benchmark the measurement to the limit specified in this legislation.”

Chevrier notes one of the biggest changes in the legislation is that the person conducting the air sampling must be knowledgeable and trained in industrial hygiene practices, which will have a significant impact on industry in Ontario.  

“Right now, there are no regulations that indicate who should be conducting industrial hygiene sampling, which may lead to improper techniques or practices being used. These new regulations state that anytime you do any monitoring or sampling, these have to be performed by a person who is qualified because of their knowledge, training, and experience with recognized IH [industrial hygiene] practices.” 

Top 5 Proposed OEL Changes

The tables posted on the MOL website contain new or revised OELs and listings proposed for 21 substances resulting from changes recommended by the American Conference of Governmental Industrial Hygienists. 

  1. Addition of specific listings for four substances to regulation: Ethyl isocyanate, Peracetic acid, Phenyl isocyanate and Cyanogen bromide. 

  2. Revisions to exposure limits or listings for 17 substances currently regulated: Acetone, Atrazine, Barium sulfate, 1-Bromopropane, Ethylidene norbornene, Lithium hydride, Methomyl, Methyl formate, Methyl isocyanate, Naphthalene, Nickel carbonyl, Oxalic acid, Pentachlorophenol, Pentane, and Trichloroacetic acid, 1,2,3 –Trichloropropane, and Triethylamine.

  3. Proposed new respiratory protection requirements: Currently, there are guidelines, but no specific law addressing the care, selection and use of respiratory protection. The proposed new law would require employers to ensure respiratory equipment is appropriate, and to establish written measures and procedures that address the selection, care and use of the equipment. Employers would also be required to ensure that workers are provided with instruction and training in the care and use of the equipment.

  4. Introduction of new respiratory protection and measuring provisions (air sampling), which must be performed by a qualified person. Proposed provisions include changes to the minimum oxygen content and the frequency of medical tests for workers exposed to asbestos. Employers would be required to create and maintain maintenance records for powered air-purifying respirators, airline respirators and self-contained breathing apparatuses.

  5.  Proposed new air sampling requirements: Employers to ensure procedures for monitoring, sampling and determining airborne concentrations of chemical substances and worker exposure to the listed substances: (i) are carried out in accordance with a standard method for workplace sampling and analysis published by recognized institutions listed on the MOL website; and (ii) be performed by a person who is qualified because of knowledge, training and experience in accordance with recognized industrial hygiene practice.

Details on all proposed changes are available on the Ministry of Labour website

For more information, contact

How to participate

Stakeholders are invited to submit comments on any or all of the proposed changes affecting the control of hazardous substances under the Occupational Health and Safety Act. Specific concerns should contain a clear description of the rationale and supporting documentation. Further information about the intended changes and how stakeholders can comment is available at the American Conference of Governmental Industrial Hygienists’s “Notice of Intended Changes.”

The 60 day consultation period ends June 6, 2016. Submissions may be emailed to


Industrial Hygiene Testing

Radon Testing

Mine ventilation assessment services

How to meet legislated training standards for both WHMIS 1988 and 2015