“The Miracle Mineral”
Asbestos is a naturally occurring mineral with long thin crystals that can be crushed to produce a multitude of silky filaments. Flexible yet tough, asbestos is resistant to heat and corrosion and does not conduct electricity. The filaments can be spun and woven into textiles for fireproof insulation products or they can be mixed with cement to reinforce construction materials.
Fifty years ago asbestos was called the “Miracle Mineral” [infographic] and was considered a natural resource that would bring Canada, a leading producer, long-term prosperity.1 Since then, we have learned that not only are asbestos fibres extremely durable, they also cause lung disease and disability many years after exposure. Due to the long latency period, the incidence of malignant mesothelioma, an asbestos-related lung cancer, continues to rise in Canada despite the restrictions on asbestos use that began over 30 years ago.
Forms of Asbestos
The two classes of asbestos are serpentine, with its curly fibres, and amphibole, with its needle-like fibres. Asbestos mines often contain a mix of serpentine and amphibole minerals.
Chrysotile (also called white asbestos) is the only member of the serpentine class and is used more than any other form of asbestos, usually for construction and textiles. The most commonly used members of the amphibole class, crocidolite (brown asbestos) and amosite (blue asbestos), are resistant to heat and strong acids and have more specialized uses than white asbestos (Figure 1).
Modern History of a Carcinogen
1858 – Asbestos industry established in the US with mining of asbestos for insulation on Staten Island, New York.
1878 – Asbestos production begins in Canada at Thetford Mines, Quebec.
1924 – In Britain, an inquest into a textile worker’s death leads to the first medical description of asbestosis.
1938 – Lung cancer is declared an occupational disease of asbestos workers by German pathologist Martin Nordmann.
1955 – Richard Doll’s paper “Mortality from lung cancer in asbestos workers” is published.
1987 – The International Agency for Research on Cancer (IARC) declares asbestos a human carcinogen.
2007 – The Canadian Cancer Society calls for the Canadian government to phase out use and export of asbestos.
- 1. Canadian Broadcasting Company (CBC). Asbestos: the magic mineral that was once Canada’s gold. Canada: [publisher unknown]; 2008 [updated 2009 Jun 10]. http://www.cbc.ca/canada/story/2009/06/10/f-asbestos-safety.html
- 2. International Agency for Research on Cancer (IARC). IARC Monographs on the Evaluation of Carcinogenic Risks to Humans: Asbestos. 1987; Supplement 7.
- 3. International Agency for Research on Cancer (IARC). IARC Monographs on the Evaluation of Carcinogenic Risks to Humans: Asbestos. 1977; Volume 14: 106-117.