Asbestos became increasingly popular among manufacturers and builders in the late 19th century because of its sound absorption, average tensile strength, its resistance to fire, heat, electrical and chemical damage, and affordability. It was used in such applications as electrical insulation for hotplate wiring and in building insulation. When asbestos is used for its resistance to fire or heat, the fibers are often mixed with cement (resulting in fiber cement) or woven into fabric or mats.
Asbestos mining began more than 4,000 years ago, but did not start large-scale until the end of the 19th century. For a long time, the world's largest asbestos mine was the Jeffrey mine in the town of Asbestos, Quebec.
One of the main problems with asbestos now comes from sprayed or "friable" (easily broken up) asbestos used in buildings until the 1970s. Construction workers, tradespeople and other building maintenance workers may be exposed to very high concentrations of asbestos fibres during renovations and repairs to older buildings. The environment and work methods of these occupations are more difficult to control than fixed workplaces. However, most tradespeople are trained in the proper handling of materials that contain asbestos.
Because it is a valuable reinforcing, insulating, and fire-proofing material, asbestos was used widely in construction materials, like:
- insulation board
- asbestos cement
- floor and ceiling tiles
- drywall joint cement
These products do not release significant amounts of fibres under normal use. However, you can release fibres if you cut or damage these products.
Levels of asbestos fibres in the air in buildings are usually about the same as in the air outside and are not a significant risk. But levels may be higher if you disturb asbestos materials that are friable (easily broken up).
There is also concern about vermiculite insulation, which may contain small amounts of amphibole asbestos, primarily tremolite or actinolite. The amphibole fibres may cause health risks if disturbed. But there is currently no evidence of risk to your health if the insulation is:
- sealed behind wallboards and floorboards
- isolated in an attic
- otherwise kept from exposure to the home or interior environment
The amount of asbestos in a product does not indicate its health risk. If the asbestos fibres stay enclosed or tightly bound in a product, there is no significant health risk.
Asbestos poses health risks only when fibres are present in the air you breathe. How exposure to asbestos can affect you depends on:
- the amount of asbestos fibres in the air
- how long your exposure lasts
- how often you were exposed
- the size of the asbestos fibres inhaled
- the amount of time since your first exposure
- the type of asbestos fibre
When inhaled in significant quantities, asbestos fibres can cause:
- asbestosis - a scarring of the lungs that makes breathing difficult
- mesothelioma - an otherwise rare cancer of the lining of the chest or abdominal cavity
- lung cancer
- cancer of the larynx
- ovarian cancer
There is also evidence that asbestos can cause cancer of the pharynx and stomach. The link between exposure to asbestos and other types of cancers is less clear.
Smoking, combined with inhaled asbestos, greatly increases the risk of lung cancer.