Asbestos is a naturally occurring fibrous mineral. There are 2 groups of asbestos fibres: serpentine and amphibole.
- Serpentine fibres are long, flexible, and curved. The only type of serpentine asbestos is chrysotile. Chrysotile asbestos is sometimes also called white asbestos.
- Amphibole fibres are straight and rigid. There are 5 types of amphibole asbestos: crocidolite (blue asbestos), amosite (brown asbestos), actinolite, anthophyllite, and tremolite.
All types of asbestos are hazardous and can cause:
- Asbestosis, a pulmonary fibrosis/pneumoconioses
- Gastrointestinal cancers (stomach, esophagus, colon, rectum)
- Laryngeal cancer (cancer of the larynx)
- Lung cancer
- Mesothelioma, a rare cancer of the pleura of the lungs
- Ovarian cancer
- Pleural diseases (pleural plaques, diffuse pleural fibrosis, pleural effusion)
According to the scientific literature, exposure to asbestos is also positively associated with: idiopathic pulmonary fibrosis (IPF), sarcoidosis, scleroderma, rheumatoid arthritis, among several other diseases.
Asbestos has been in use for thousands of years in the production of clay pottery and cloth including funeral shrouds, napkins, tablecloths, and wicks. It became even more widely mined and used during the Industrial Revolution, starting in Thetford Mines, Quebec in the 1870s. The demand for asbestos continued to increase into the 20th century, until peak consumption was reached in the 1960s and 1970s. Although the records of adverse health effects experienced by asbestos miners and millers date back to the late 1890s and early 1900s, it wasn’t until the late 1970s that asbestos use declined, and it became strictly regulated in Ontario under the Occupational Health and Safety Act in 1985. Canada stopped mining asbestos in 2012 and new asbestos use was banned in Canada in 2018.
Asbestos fibres were prized for their tensile strength, thermal insulation, and resistance to chemicals, fires, and electric current. They also do not dissolve in water or evaporate, are resistant to biological breakdown, and have sound absorbing properties. Thanks to these physical properties, asbestos was used extensively in construction, and as such it is still found in many existing buildings, including in:
|· Acoustic ceiling tiles|
· Blankets (fire blankets, baby blankets)
· Cement or “transite” pipes, wallboard, roofing, siding
· Construction mastics
· Drywall joint compound
· Electrical wiring
· Fire doors
|· Friction linings (brake pads, gaskets)|
· Heating and electrical ducts
· Plaster walls, ceilings
· Pipe insulation (corrugated paper or “Aircell”, parging, cement, block)
· Roofing felt, roofing shingles
· Sprayed on insulation
· Vinyl flooring (sheets, tiles)
Asbestos is only hazardous when it is inhaled, or, less frequently, ingested. In many situations, inhalation only occurs when asbestos is in poor condition or is disturbed. However, given how much asbestos still exists in building, care must be taken to identify asbestos before disturbing building materials that may contain asbestos.
Exposure to asbestos can also occur “secondhand”, also called a secondary exposure or take-home exposure. Secondary exposures happened when a worker inadvertently brought asbestos home, often on their clothing, skin, or hair. The worker didn’t always know the dust or dirt on them contained asbestos. One common situation was the asbestos-exposed worker’s wife would be exposed while cleaning asbestos-contaminated laundry. Another common situation was children exposed when hugging their parent who had asbestos on their hair, skin, and clothes. Then after this hug, small (microscopic) asbestos fibres could also linger in the air. These secondary exposures are just as dangerous as primary exposures.
If asbestos is in good condition and is not disturbed, the risk of inhaling asbestos is low. But for asbestos in poor condition or that may be disturbed, asbestos fibres could be inhaled. When there is a potential for exposure to asbestos fibres, control measures such as engineering controls, administrative controls, and/or personal protective equipment (PPE) may be needed. Engineering controls could include making a negative pressure enclosure around the product containing asbestos. Administrative controls include policies and procedures for working with the asbestos-containing material. Examples of PPE will depend on the amount of asbestos being made airborne and/or the type of asbestos work or abatement being done. It can include a full-face respirator with a P100 cartridge, a powered air-purifying respirator with a P100 cartridge, as well as impermeable, disposable clothing.
Health Effects of Asbestos (presentation)
Practical Tools for Working on Occupational Cancer Cases: Case Studies of Lung Cancer (slides)
Mesothelioma Cases with Unusual Exposures (OHCOW poster) – see email for attachment as I can’t find it online
Asbestos in the Workplace (Ontario Ministry of Labour, Immigration, Training and Skills Development)
OEL Tool (OHCOW Tool link)