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Asbestos and drinking water in Canada.
The Science of the Total Environment
|April 1, 1981
Summary
Chrysotile asbestos was found in Canadian drinking water, but treatment effectively removed it. While some water pipes may release asbestos, the study found no definitive link to gastrointestinal cancer mortality, suggesting occupational exposure may be a factor.
Area of Science:
- Environmental Science
- Public Health
- Toxicology
Background:
- Asbestos contamination in drinking water is a public health concern.
- Chrysotile asbestos is the predominant type found in Canadian water supplies.
Purpose of the Study:
- To assess asbestos levels in Canadian drinking water.
- To evaluate the efficacy of water treatment processes for asbestos removal.
- To investigate potential associations between asbestos in drinking water and gastrointestinal cancer mortality.
Main Methods:
- Transmission electron microscopy (TEM) was used to quantify asbestos content in water samples from 71 Canadian municipalities.
- Age-standardized mortality rates for gastrointestinal cancers (1966-1976) were analyzed.
- Mortality rates in high-asbestos areas were compared to low-asbestos areas.
Main Results:
- Approximately 5% of public water supplies exceeded 10 million asbestos fibers per liter.
- Coagulation/filtration treatment demonstrated high efficiency in removing chrysotile asbestos (improvement factors up to 300).
- Elevated mortality rates for certain gastrointestinal cancers were observed in specific high-asbestos localities, but potential occupational exposures complicate direct attribution.
Conclusions:
- Water treatment effectively reduces asbestos concentrations.
- Evidence suggests asbestos can erode from water pipes.
- A direct link between asbestos in drinking water and gastrointestinal cancer mortality was not definitively established, warranting further investigation into occupational exposures.