Drinking water and cancer

Our plain-English summary of Drinking water and cancer, by R.D. Morris (Environmental Health Perspectives, 1995).

The study

• Author: R.D. Morris
• Journal: Environmental Health Perspectives
• Published: 1995;103 Suppl 8(Suppl 8):225-31
• Type of article: Review
• Cited by: 63 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Any and all chemicals generated by human activity can and will find their way into water supplies. The types and quantities of carcinogens present in drinking water at the point of consumption will differ depending on whether they result from contamination of the source water, arise as a consequence of treatment processes, or enter as the water is conveyed to the user. Source-water contaminants of concern include arsenic, asbestos, radon, agricultural chemicals, and hazardous waste. Of these, the strongest evidence for a cancer risk involves arsenic, which is linked to cancers of the liver, lung, bladder, and kidney. The use of chlorine for water treatment to reduce the risk of infectious disease may account for a substantial portion of the cancer risk associated with drinking water. The by-products of chlorination are associated with increased risk of bladder and rectal cancer, possibly accounting for 5000 cases of bladder cancer and 8000 cases of rectal cancer per year in the United States. Fluoridation of water has received great scrutiny but appears to pose little or no cancer risk. Further research is needed to identify and quantify risks posed by contaminants from drinking-water distribution pipes, linings, joints, and fixtures and by biologically active micropollutants, such as microbial agents. We need more cost-effective methods for monitoring drinking-water quality and further research on interventions to minimize cancer risks from drinking water.

In plain English

This article was a review, presented at a 1994 President's Cancer Panel conference, of evidence on cancer risks from contaminants entering U.S. drinking water through source water, treatment, or distribution pipes. It reported no new asbestos study and named no asbestos fiber types. Citing earlier studies, the author wrote that risks attributable to asbestos in drinking water did not appear substantial. An early California study suggested a possible rise in colorectal cancer risk, but later work suggested asbestos at commonly found levels does not pose a major cancer risk. Research on asbestos leaching from asbestos-concrete pipes suggested no significant human cancer risk. The author placed the strongest evidence on arsenic and chlorination by-products. An earlier meta-analysis found statistically significant risk elevations for bladder and rectal cancer. The author's own mapping of Medicare data for people over 64 showed significant clustering of gastrointestinal and bladder cancers in the northeastern United States, though the author called any link to drinking water premature. The author concluded that radon and asbestos risks were less substantial but may require remediation where local conditions dictate.

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 (conference paper) of cancer risks from drinking-water contaminants, with an added geographic mapping of cancer incidence by the author
• Who was studied: Mainly published studies of drinking water and cancer, largely in the United States. The author's own mapping used Medicare hospital admissions data for persons over 64, 1988 to 1989.
• Exposure: Drinking-water contaminants entering through the source water (arsenic, asbestos, radon, agricultural chemicals, hazardous waste), through treatment (chlorination by-products, fluoride), and through distribution (including asbestos leaching from asbestos-concrete pipes). No asbestos fiber types are named.
• Main results:
  • Asbestos in source water: the author wrote that the attributable risks associated with asbestos in drinking water do not appear to be substantial.
  • An earlier California study (cited, not this article's) suggested there may be an elevation in colorectal cancer risk associated with asbestos in drinking water. The author wrote that these findings appear limited to situations where naturally occurring levels are high.
  • Citing later studies, the author wrote that asbestos at levels commonly found in drinking water does not pose a major cancer risk.
  • Asbestos leaching from asbestos-concrete pipes: the cited research suggests asbestos from this source does not pose significant human cancer risks.
  • Of the source-water contaminants, the author described some of the strongest evidence of cancer risk as involving arsenic.
  • In an earlier meta-analysis of chlorination by-products (cited), risk estimates were statistically significant for bladder and rectal cancer.
  • Figures derived from that meta-analysis suggest that 5000 (95% CI 2000 to 7000) bladder cancer cases and 8000 (95% CI 200 to 14,000) rectal cancer cases per year in the United States may be associated with chlorinated drinking water.
  • A cited estimate suggests that fewer than 100 cancer cases per year in the United States result from consuming radon in drinking water.
  • The author wrote that the available evidence does not support cancer risks from fluoridation.
  • The author's own map of persons 65 and older showed significant clustering of elevated rates of gastrointestinal and bladder (mucosal) cancers in the northeastern United States.
• The authors' conclusion: The author concluded that chlorination by-products pose substantial cancer risks that should be reduced, and that cancer risks from radon and asbestos in drinking water are less substantial but may require remediation where local conditions dictate.
• Limitations the authors state:
  • The author stated that epidemiologic evidence on cancer risks from contamination during distribution is extremely limited.
  • The author stated that drawing conclusions about a link between the mapped cancer pattern and drinking water would be premature.
  • The author stated that the bladder and rectal cancer case estimates are not precise.

Related studies

• Cancer incidence and asbestos in drinking water, Town of Woodstock, New York, 1980-1998 — M.L. Browne, D. Varadarajulu, et al. (2005)
• Asbestos-contaminated drinking water: its impact on household air — J.S. Webber, S. Syrotynski, et al. (1988)
• Cancer of the gastrointestinal tract and exposure to asbestos in drinking water among lighthouse keepers (Norway) — K. Kjaerheim, B. Ulvestad, et al. (2005)
• Drinking water and cancer — K.P. Cantor (1997)
• Cancer incidence following exposure to drinking water with asbestos leachate — H.L. Howe, P.E. Wolfgang, et al. (1989)
• Asbestos in drinking water and cancer incidence in the San Francisco Bay area — M.S. Kanarek, P.M. Conforti, et al. (1980)

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