Asbestos in drinking water and cancer

Our plain-English summary of Asbestos in drinking water and cancer, by K.D. MacRae (Journal of the Royal College of Physicians of London, 1988).

The study

• Author: K.D. MacRae
• Journal: Journal of the Royal College of Physicians of London
• Published: 1988;22(1):7-10
• Type of article: Review
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Free full text

In plain English

This 1988 article was a review, not a new study. The author assessed epidemiological studies of asbestos in drinking water, from natural rock, dumped waste or asbestos-cement pipes, and cancer. Most were geographical correlation studies, from Duluth, Connecticut, Quebec, the San Francisco Bay area and Puget Sound. Problems included single-sample fibre counts, unaddressed dietary asbestos, and long cancer latency, making it uncertain whether those with cancer were those exposed. The Duluth studies concerned amphibole; the others, chrysotile. The author judged the Quebec and Puget Sound studies strongest; they gave largely negative findings despite high fibre levels. Some studies found statistically significant associations, mainly for gastrointestinal cancers, but the author called risk elevations minimal and inconsistent. The author concluded most cancer sites showed no excess risk even at high levels. A minimal raised risk for some gastrointestinal sites from high levels over many years was possible, but no risk was more probable. Low levels, or high levels for short periods, were judged highly unlikely to raise risk. Asbestos released from asbestos-cement pipes was highly improbable to be relevant to cancer.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Narrative review of published epidemiological studies of asbestos in drinking water and cancer. No search method is described.
• Who was studied: Published studies reviewed: five major groups (Duluth, Minnesota; Connecticut; Quebec; San Francisco Bay area; Puget Sound, Western Washington), plus smaller studies from Florida and Utah and a US-wide study of natural asbestos deposits
• Exposure: Asbestos fibres in drinking water from three sources: naturally occurring asbestos in source rocks, dumped asbestos-containing waste, and asbestos-cement water pipes
• Main results:
  • Fibre types: the Duluth (waste contamination) studies concerned amphibole. All the other studies concerned chrysotile.
  • Quebec studies: the author reported only slightly elevated risk ratios for stomach cancers in males and in females. The author added that these could have occurred by chance, from occupational exposure, or from unknown variables.
  • San Francisco Bay studies: some cancer sites showed statistically significant relative risks, but the author said they were only minimally above 1. The author also doubted they could be taken at face value because of high population mobility.
  • Puget Sound study, judged by the author the most rigorous: the high-exposure population was only 77,000, with a mean of 200 million fibres/litre compared with a mean of 7.3 million fibres/litre in the low-concentration group.
  • Puget Sound follow-up case-control study: cases and controls had similar asbestos exposure. The author said this added to the negative findings of most correlation studies.
  • Duluth studies: the author said they lacked the power to detect a small relative risk.
  • Duluth studies: the observation period was short compared with the expected latency of asbestos-related cancer.
  • Connecticut asbestos-cement pipe studies: asbestos levels in drinking water were usually less than 1 million fibres per litre. The author judged the results of limited value.
  • Connecticut data: in 19 water samples taken after the water had passed through asbestos-cement pipes, chrysotile counts ranged from below detectable limits to 700,000 fibres/litre.
  • Across studies: the statistically significant associations, mainly for gastrointestinal tract cancers, involved minimal elevations in risk ratios and were not found consistently.
  • The author judged that the associations found did not meet the Bradford Hill criteria for causality.
  • The author judged it highly unlikely that low levels of asbestos (even for long periods), or high levels for short periods, give rise to any excess cancer risk at any site.
  • The author judged it highly improbable that asbestos released from asbestos-cement pipe is relevant to cancer.
• The authors' conclusion: The author concluded that for most cancer sites, all ages and both sexes, no excess risk appeared even from high levels of asbestos in drinking water. For some gastrointestinal sites, a minimal raised risk from high levels over many years was possible, but no risk was more probable.
• Limitations the authors state:
  • The review did not consider in detail animal toxicology, gastrointestinal penetration by fibres, in vitro testing, water aggressiveness studies or engineering controls.
  • In the studies reviewed, fibre counts were nearly always based on single water samples. One study of replicate counting in separate laboratories found a 400-fold difference.
  • None of the drinking-water studies reviewed addressed possible confounding by asbestos in the diet.
  • The long latent period of cancer makes it uncertain in geographical correlation studies whether the diseased population is the exposed population.

Related studies

• Cancer incidence in relation to asbestos in drinking water in the Puget Sound region — L. Polissar, R.K. Severson, et al. (1982)
• A case-control study of asbestos in drinking water and cancer risk — L. Polissar, R.K. Severson, et al. (1984)
• Asbestos-contaminated drinking water: its impact on household air — J.S. Webber, S. Syrotynski, et al. (1988)
• Asbestos in water — R. Murray, K. Browne (1981)
• "Asbestos in drinking water and cancer incidence in the San Francisco Bay area" — K. Browne (1982)
• Asbestos in public water supplies: discussion of future problems — J.P. Hills (1979)

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