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Designated Substances in Ontario

Written by: Lisa Hallsworth

Published on: 8 March 2017

Updated: Nov. 16, 2022

Danger sign warning of asbestos, a designated substance

What are designated substances?

Ontario’s Occupational Health and Safety Act (OHSA) defines a “designated substance” as “a biological, chemical or physical agent or combination thereof prescribed as a designated substance to which the exposure of a worker is prohibited, regulated, restricted, limited or controlled.”

Designated substances are known to result in health problems (such as cancer, severe allergic reactions, genetic defects and organ disease) if handled improperly.

There are 11 designated substances in Ontario: Ontario Regulation 490/09 under the OHSA consolidates the 11 stand-alone regulations for designated substances being used, handled or stored in the province. It came into effect on July 1st, 2010. O. Reg. 278/05: Designated Substance – Asbestos on Construction Projects and in Buildings and Repair Operations is the only regulation that was not consolidated.

What chemicals does O. Reg. 490/09 cover?

In Ontario, 11 designated substances are listed in Table 1 of Ontario Regulation 490/09, along with exposure limits for each:

  • Acrylonitrile
  • Arsenic
  • Asbestos
  • Benzene
  • Coke Oven Emissions
  • Ethylene Oxide
  • Isocyanates
  • Lead
  • Mercury
  • Silica and
  • Vinyl Chloride

As noted above, asbestos on construction projects and building or repair operations is regulated under O. Reg. 278/05.

Do designated substance regulations apply to me?

If you use, handle or store any of the 11 designated substances or if ingredients of chemical products that you use, handle or store are listed in Table 1 of O. Reg. 490/09, then the regulations apply to you.

How do I know if products contain designated substances?

Your WHMIS safety data sheets (SDSs) are the best resource to determine if chemical products contain designated substances.  Section 3 of the SDS lists all hazardous chemical ingredients by name, Chemical Abstract Service (CAS) number and percentage composition. You must compare the ingredient CAS # to those in Table 1 of the regulation.

For example, many commonly used adhesives and spray foams contain large percentages of the isocyanates listed in Table 1. The time-weighted average exposure limits for isocyanates are exceedingly low: – 0.005 ppm and the ceiling exposure limit can be as low as 0.015 ppm, meaning that in a 10 ft by 10 ft by 8 ft room, a worker would be above the ceiling exposure with a tenth of a teaspoon of vapour dispersed in the room! These products must be used with great care in the workplace or in any other location with limited ventilation.

Learn more about the challenges of managing isocyanates and other designated substances.

I handle, use or store designated substances. Now what?

If you have designated substance ingredients in your workplace, you must assess the likelihood of employee exposure to the designated substance and record this in writing (O. Reg. 490/09, s.19 (1)).   The assessment is best done by a qualified industrial hygienist. Depending on the results of this assessment, further actions may be required to properly comply with the regulation.  A qualified safety professional can help you understand the requirements.

There are a number of steps you can take to manage designated substances. One of the easiest is to simply eliminate the use of the chemical product by replacing it with another, safer product. SDS RiskAssist technology makes this a snap by showing you alternative products at the click of a mouse:

SDS RiskAssist - search for safer chemical products
Actual product and supplier names not included this example.

Contact SDS RiskAssist if you require further information or help identifying chemical products that contain designated substance ingredients.



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SDS RiskAssist an Ontario-based company that uses the power of technology to give employers control and understanding over the otherwise pervasive and worrisome use of chemicals. SDS RiskAssist enables workers to know why chemicals are being used, what their benefits and hazards are and how to use them safely! Workers can access this knowledge via mobile or desktop SafetySnaps™, from anywhere in the world. SDS RiskAssist is the winner for 5 years running, of Readers’ Choice Awards by Canadian Occupational Safety Magazine (2018-2022); the 2019 Innovation Guelph Startup of the Year Award; the 2019 Quinte Business Achievement Award (Trailblazer category) and The Ottawa Network’s 2020 Bootstrap Award (SaaS category). We support the United Nations Sustainable Development Goals, working with our clients to take action for a sustainable planet.

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