Drinking water and cancer

Our plain-English summary of Drinking water and cancer, by K.P. Cantor (Cancer Causes & Control, 1997).

The study

• Author: K.P. Cantor
• Journal: Cancer Causes & Control
• Published: 1997;8(3):292-308
• Type of article: Review
• Cited by: 199 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Epidemiologic evidence on the relation between contaminants in drinking water and cancer is reviewed. The reviewed studies cover exposure to: disinfection byproducts; nitrate; arsenic and other metals; volatiles and contaminants from hazardous waste sites; asbestiform fibers; radionuclides; and fluoride. Most investigations are ecologic, with some confirmation of elevated risk from individual-based studies. In the case of waterborne arsenic, and possibly chlorination byproducts, there is a consistent but small body of epidemiologic evidence of an association with one or more types of cancer. Nitrate in groundwater has increased greatly over the years, and the demonstration of endogenous nitrosation among highly exposed subjects raises concern of elevated cancer risk. However, the epidemiologic data are not yet sufficient to draw a conclusion. There is a diversity of studies among populations exposed to water contaminated with pesticides, volatile organics, or mixtures from hazardous waste sites. Studies of asbestiform fibers and radionuclides in water are not conclusive, but there are suggested elevations of several cancer sites in highly exposed populations. There is no suggestion that fluoride in drinking water is linked with elevated risk of cancer. As topics for epidemiologic evaluation, drinking water contaminants pose methodologic problems common to studies designed to detect relatively small elevations in risk, with the added challenge of assessing exposures for many years in the past. Nevertheless, epidemiologic assessment is valuable and clearly warranted, given the potential public health impact of small risk elevations among very large exposed populations, and the limitations of toxicologic experiments in assessing carcinogenic risk of complex mixtures or of compounds for which appropriate animal models are not available.

In plain English

This 1997 article by K.P. Cantor was a review of published epidemiologic studies of drinking water contaminants and cancer, not a new study. It covered chlorination byproducts, nitrate, arsenic and other metals, industrial and hazardous-waste chemicals, asbestos, radionuclides and fluoride. It noted that most studies were ecologic, meaning they compared areas rather than individuals. For asbestos, the review described studies from the San Francisco Bay area, Canadian cities, Puget Sound, Duluth, Norwegian lighthouse keepers, and towns with asbestos-cement water pipes. Results were mixed. Some studies reported associations with stomach, pancreas, kidney or other cancers, while others found no association or inconsistent patterns. Among the Norwegian lighthouse keepers, gastric cancer was 2.4-fold higher in those first exposed at least 20 years before diagnosis. The author concluded that the evidence was not adequate to evaluate the cancer risk from asbestos in drinking water. The author also noted suggested elevations of gastric, kidney and pancreas cancers that warranted further investigation. The author named small relative risks and the difficulty of estimating past exposures as general problems in this research.

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: review of published epidemiologic studies (not an original study)
• Who was studied: Published epidemiologic studies, mostly ecologic, of populations exposed to drinking water contaminants in many countries. For asbestos: the San Francisco Bay area, Quebec, 66 Canadian cities, Puget Sound (Washington State), Duluth (Minnesota), Norwegian lighthouse keepers, and communities with asbestos-cement water mains in Connecticut, Utah, Woodstock NY and a Florida county.
• Exposure: Contaminants in drinking water: disinfection (chlorination) byproducts, nitrate, arsenic and other metals, volatiles and hazardous-waste contaminants, asbestiform fibers, radionuclides and fluoride. For asbestos, the review describes sources as natural deposits such as serpentine, asbestos-cement pipes, and iron ore (taconite) processing tailings in Lake Superior. Specific asbestos fiber types are not named in the review's text.
• Main results:
  • The review described two related San Francisco Bay area studies (by other authors). They found associations between naturally occurring asbestos in drinking water and incidence of cancers of the esophagus, stomach and pancreas in both genders, of the lung in males, and of the gall bladder and peritoneum in females.
  • The review described a study of 66 Canadian cities that found no association between asbestos in water and all-cause mortality, total cancer mortality, or mortality from several cancer sites, including stomach.
  • The review described a Puget Sound case-control study, which observed positive associations for male stomach cancer based on small numbers.
  • The review described a cohort study of Norwegian lighthouse keepers exposed to asbestos in drinking water. It reported an excess of gastric cancer, with a 2.4-fold excess among persons first exposed at least 20 years before diagnosis.
  • For Duluth, where drinking water carried taconite tailings from 1955 to 1973, the reviewed studies found some excesses of gastrointestinal mortality and morbidity, but the patterns of risk were inconsistent.
  • Studies of asbestos-cement water mains had inconsistent findings. In Utah, an association was found for kidney cancer (males) and leukemia (females). In Woodstock, NY, an association was found for cancer of the oral cavity.
  • Outside asbestos, the review judged that the studies it covered provide evidence that arsenic in drinking water poses a threat of internal cancer, with bladder and lung cancers showing the strongest associations.
• The authors' conclusion: The author concluded that the epidemiologic evidence was not adequate to evaluate the cancer risk posed by asbestos in drinking water. The author added that suggested elevated risks for gastric, kidney and pancreas cancers in the cited studies warrant further investigation.
• Limitations the authors state:
  • The author noted that relative risks in this field are generally small, in a range where uncontrolled confounding or other bias may be important.
  • The author noted that having to estimate contaminant levels many years in the past can cause misclassification of exposure, which can weaken observed associations.

Topics

Medical terms in this study, explained in our Lexicon: Asbestiform, Carcinogenic.

Related studies

• Chemical contamination of California drinking water — H.H. Russell, R.J. Jackson, et al. (1987)
• The control of potential health risks related to drinking water in the UK — T.A. Dick (1981)
• Cancer incidence following exposure to drinking water with asbestos leachate — H.L. Howe, P.E. Wolfgang, et al. (1989)
• Drinking water and cancer — R.D. Morris (1995)
• Cancer incidence and asbestos in drinking water, Town of Woodstock, New York, 1980-1998 — M.L. Browne, D. Varadarajulu, et al. (2005)
• A case-control study of asbestos in drinking water and cancer risk — L. Polissar, R.K. Severson, et al. (1984)

Browse more research in Cancer Causes & Control, or return to medical research.