Designated substances in Ontario: the list and what owners need to know

Ontario's Occupational Health and Safety Act names a set of "designated substances": materials that are hazardous enough to have their own rules for workplaces and construction projects. If you own or manage a commercial building, these substances matter most when work is about to disturb the building's materials. This page lists them, explains which ones commonly turn up in commercial buildings, and sets out what owners are generally expected to do. It is an overview, not legal advice; confirm requirements for your project.

A designated substance is one Ontario has singled out under the Occupational Health and Safety Act because worker exposure to it has to be controlled. Ontario Regulation 490/09 lists 11 of them and sets out how employers assess and control exposure. Asbestos on construction projects and in buildings also has its own regulation, O. Reg. 278/05. For a building owner the practical point is simpler: if any of these substances is present where work will happen, it has to be identified before the work is tendered and dealt with before other trades disturb it.

The designated substances list is:

1. Acrylonitrile
2. Arsenic
3. Asbestos
4. Benzene
5. Coke oven emissions
6. Ethylene oxide
7. Isocyanates
8. Lead
9. Mercury
10. Silica
11. Vinyl chloride

Some of these mainly concern specific industrial processes. Others are found in ordinary building materials.

For most offices, retail, industrial units and institutional buildings, the substances that come up in practice are:

• Asbestos: in older drywall joint compound, plaster, floor tiles, ceiling tiles, insulation and fireproofing. Ontario Reg. 278/05 governs asbestos work on construction projects and in buildings.
• Lead: in older paints and coatings on walls, steel, doors and frames.
• Mercury: in fluorescent lamps, thermostats and some switches.
• Silica: in concrete, masonry and other materials, where cutting, grinding or breaking creates dust.

Arsenic, vinyl chloride and the others are less common in building materials but can be relevant in particular industrial facilities.

Before a construction project begins, the owner is expected to prepare a list of the designated substances present at the project site and give it to prospective contractors, so they can price and plan the work safely. Contractors then pass that information to their subcontractors. In practice, this means:

• Identifying designated substances in the areas the work will affect, before tendering
• Including the findings in the tender or project documents
• Updating the information when the scope changes
• Keeping records of what was found and what was done

Specific obligations depend on the project. Confirm requirements with a qualified professional.

The usual way to identify designated substances is a survey by a qualified assessor before the work begins. Our blog on the designated substance survey for commercial renovation in Ontario explains how that survey works on a renovation or fit-out. For a wider look that can also include mould and PCBs, see our hazardous building materials assessment, where we coordinate the assessor and lab.

Demolition disturbs more of the building than a renovation, so the identification usually needs to cover more of it, including concealed areas. See our commercial demolition services for how we sequence abatement ahead of demolition.

Asbestos is the designated substance owners meet most often. Ontario classifies asbestos work as Type 1, Type 2 or Type 3 according to risk, and Type 3 work usually involves a notice to the Ministry of Labour before it starts. See Type 3 asbestos notice timelines in Ontario for the lead time involved.

A few points help owners use the list well:

• Building age matters, but it isn't proof. Older buildings are more likely to contain asbestos and lead, but later renovations can introduce or hide materials, so the areas being disturbed should be checked.
• The scope drives the identification. A small fit-out on one floor needs a narrower review than a full-building renovation.
• Records carry forward. Earlier findings and abatement records help on the next project and should be kept with the building's documents.
• Tenants and contractors need the information. Sharing it early avoids surprises after work has started.

Ontario amends its occupational health regulations from time to time, including exposure limits and how particular substances are handled, and older specifications and guidance pages can lag behind. Before relying on a list or a limit in an old report, check the current versions of O. Reg. 490/09 and O. Reg. 278/05 on Ontario's e-Laws site, and ask your assessor whether the survey reflects current requirements.

Sofisa Group Inc. is a WSIB-cleared and insured Ontario commercial general contractor and abatement contractor based in Mississauga. We are not an assessor or a lab. If you have findings already, or need them arranged, contact us. When designated substances are identified in the areas you plan to disturb, we carry out the asbestos abatement and other removal work, then the demolition or construction that follows. See our abatement services.