By Vivian Astroff

If your home was built before the 1980s, and you’re thinking about renovating, you and your contractor will have to take special precautions to protect workers from harmful substances that could be present in the house during demolition.

By law, a homeowner is responsible for identifying specific “designated substances” – what they are and where they are located in the building structure – before their renovation job begins. This is required by Ontario’s ministry of Health and Safety in the Occupational Health and Safety Act, updated in January 2013.

Professional renovators know this, of course, and it’s one of the many reasons why their expertise is so valuable. They are aware, for instance, that asbestos and lead are probably the most commonly occurring culprits. And they know about other, less-familiar, toxins as well – including silica, isocyanates, mercury and arsenic.

RenoMark™ renovators, in particular, frequently attend seminars in order to stay up-to-date on a wide variety of materials. When those materials are dangerous, they know how to dispose of them and how to keep you and their workers safe.

According to Health and Safety, these designated substances are hazardous when inhaled, absorbed through the skin, or ingested, so workers on the site must wear appropriate personal protective equipment. Should the substances enter the body through the skin, lungs, or digestive system, they can cause cancer, strong allergic reactions, liver and lung problems, and affect the nervous system.

In the Ottawa-Carleton region, about a dozen companies are qualified to conduct a professional survey of a residential structure, collect samples for testing, and then, based on lab results, produce a Designated Substances Survey Report describing the extent of potential contamination before demolition begins.

Rob McGrath is co-owner of Ottawa-based CM3 Environmental Inc., a company specializing in environmental consulting, and specifically surveys and assessments. McGrath explains that the size and age of the house determines the number of samples taken for testing, as well as the cost to the homeowner, which can range from about $800 to $2,000.

“Typically, samples are collected for asbestos and lead,” he says.



Asbestos is a strong mineral fibre used extensively up to the 1980s for its fire- and heat-resistant properties. It was also added to cement and plaster to give them more structural strength.

Asbestos can be found in some 3,000 materials and building products, McGrath estimates, from drywall compound and plaster, reflectant foil, vermiculite insulation, ductwork, piping and roofing shingles, to the adhesive used for tiles.

The health hazards of asbestos became public in the late 1970s, when the United States federal government began regulating its use, and Ontario soon followed suit.

If asbestos-containing materials are in good condition and left intact, they aren’t likely to release asbestos fibres. They become a hazard when they deteriorate or when they are handled, sanded, drilled into, or broken up. The fibres are extremely fine and can stay in the air for hours. Asbestos-containing materials should be identified and removed by a contractor trained in asbestos removal, wearing protective clothing and a respirator.



Lead is another hazardous substance, commonly found in house paint from the 1970s or earlier. Its purpose was to resist mould, mildew and moisture, and prevent paint from peeling. When dry lead paint is removed, the airborne dust becomes a source of toxicity. Lead may also be found in old mortar, old water pipes, sheeting used for sound control, and contaminated soil.

Lead poisoning can cause problems throughout the human body: to the hormones, red blood cells, the nervous system and bones.



Silica is a common substance composed of tiny quartz crystals found in building materials such as granite, concrete, cement and brick. Fibre cement board, for example, could contain up to 90 per cent crystalline silica. While harmless if undisturbed, cutting, grinding, or drilling these materials releases dangerous crystalline silica dust into the air that can cause permanent lung damage. The worksite manager must ensure proper dust controls, and workers have to use protective equipment.



Like lead and asbestos, mercury is a toxic substance often found in older homes, typically in old light switches, fluorescent lights, old heaters, thermostats and thermometers. While the skin cannot absorb metallic mercury, the spilled substance can vaporize into an odourless, colourless gas that is inhaled and absorbed into the body.

Immediate cleanup of spilled mercury is a must, especially around stove burners where the mercury can vaporize. If not cleaned up quickly, mercury can become absorbed by carpets, furniture, walls, floors and other areas of the home. If it gets into the ventilation system, it can spread throughout the house.

Like lead, mercury poisoning can cause developmental problems, neurological disorders and kidney failure. Mercury exposure can also cause digestive problems and eye diseases.

Before about 2002, arsenic was a common wood preservative for structures exposed to the elements or in areas of high moisture. The wood was treated with a chemical mixture of arsenic, chromium, and copper called Chromated Copper Arsenate (CCA), which worked as an insecticide, fending off dry rot, fungi, molds, termites, and other pests. CCA-treated wood was used for decks, walkways, fences, gazebos, boat docks, and playground equipment.

Because arsenic is a known human carcinogen and is highly toxic, industry has withdrawn CCA for residential applications except in areas where it won’t come into human contact, embedded behind cladding, roofing or some other membrane. Homeowners should never burn CCA-treated wood, or use it as compost or mulch.

A number of safe wood preservatives have come onto the market over the past decade, so homeowners can choose from options such as untreated wood (like cedar), or non-wood alternatives such as plastics, metal and composite materials.


New materials

Hugh Trueman, an experienced Ottawa renovator and owner of Reno Rescue and its partner company, White Vale Construction Ltd., warns that lead hazards can lurk in new housing as well.

To avoid these hazardous substances, renovators select finishing materials, fixtures or products that have an international or national standard certification such as Canadian Standards Association (CSA) or Underwriters Laboratories (UL).

When planning the replacement structure, Trueman cautions that homeowners should select certified safe glues, laminates and other finishes. Even generally safe products, such as cork, hardwood and linoleum flooring can be a health hazard, releasing toxic dust when installed or hazardous gases long after installation, if not manufactured using non-toxic materials and processes.

“We try to source materials of reputable quality,” he says. “We want to know how they have been manufactured or put together. Cabinets, carpeting and flooring are a big concern. If they are not Canadian-made, you should check the specs and standards in the countries where they are manufactured.”