The need to control asbestos fibers in potable water supply systems

Our plain-English summary of The need to control asbestos fibers in potable water supply systems, by J.R. Millette, R.L. Boone, M.T. Rosenthal, et al (The Science of the Total Environment, 1981).

The study

• Authors: J.R. Millette, R.L. Boone, M.T. Rosenthal, L.J. McCabe
• Journal: The Science of the Total Environment
• Published: 1981;18:91-102
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Occupational studies have shown that asbestos is a human carcinogen. Because many inhaled asbestos fibers deposited in the lung are cleared and swallowed, workers are also exposed through ingestion. Of the millions of current and former workers who have been heavily exposed to asbestos, one in ten will die from cancer of the gastrointestinal tract. A number on the order of 1 in 1,000 ingested asbestos fibers penetrate the digestive tract and ingested fibers have been recovered in such tissues as kidney, intestine, liver, and urine. One animal study showed tumor production related to ingestion of asbestos-containing material but, in general, the results of seven animal feeding studies have been inconclusive. A statistically significant relationship between male lung and stomach cancer and female peritoneal, gall bladder, and esophageal cancer and asbestos counts in drinking water was determined in one epidemiology study. Increased rates for male stomach and lung, and female pancreatic cancer related to asbestos in drinking water were reported in another study but possible occupational exposure made it difficult to draw conclusions. Data on excess gastrointestinal cancer among occupational groups has been used to estimate that drinking water containing 300,000 asbestos fibers per liter over a lifetime will result in one additional cancer among 100,000 people.

In plain English

This 1981 review by U.S. Environmental Protection Agency authors gathered published evidence to argue for controlling asbestos fibers in drinking water. The review described excess digestive tract cancers in asbestos workers, including a 1964 study of insulation workers in which 29 men died of stomach, colon or rectal cancer where 9 were expected. Fiber sources included serpentine rock erosion, mining discharges and corroding asbestos-cement pipe. They compiled fiber levels from 426 U.S. supplies, noting these were not representative. One San Francisco area study reported relationships between chrysotile in drinking water and certain cancers, including white male lung cancer. A preliminary Pacific Northwest report, relying on generalized assumptions, found no association with colon, stomach, kidney or total alimentary tract cancer. Animal feeding studies were described as unresolved. The authors cited an estimate based on gastrointestinal cancer and peritoneal mesothelioma in three occupational studies. By that estimate, 300,000 fibers per liter over 70 years would result in one additional death per 100,000, or one per 200,000 counting only gastrointestinal cancer. The authors concluded the water supply community should make controlling asbestos an official policy.

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 and position paper summarizing published occupational, animal, drinking-water survey and epidemiology studies (no new data collected by the authors)
• Who was studied: No study population of the authors' own. The article reviewed published studies of asbestos workers, laboratory animals, and populations drinking asbestos-containing water, plus compiled fiber measurements from 426 U.S. water supplies.
• Exposure: Asbestos fibers in drinking water from natural erosion of serpentine rock, mining and manufacturing discharges, air pollution fallout and deteriorating asbestos-cement materials (pipe, roofing tiles). Chrysotile in most systems; amphibole fibers in Lake Superior water (Minnesota).
• Main results:
  • Reviewed occupational evidence: in a 1964 study of asbestos insulation workers by Selikoff, Churg and Hammond, 9 deaths from cancer of the stomach, colon or rectum were expected and 29 occurred, an excess of 200%.
  • Reviewed epidemiology: a San Francisco area study (Kanarek and colleagues, ref. 50) found relationships between chrysotile asbestos content of drinking water and white male lung cancer, white female gall bladder and pancreas cancer, and peritoneal cancers in both sexes.
  • Reviewed epidemiology: a preliminary report from the Pacific Northwest (ref. 54) did not show an association between fibers in drinking water and cancer of the colon, stomach, kidney, or total alimentary tract. The article notes that generalized assumptions were made at that stage and that more specific studies were underway.
  • Reviewed animal evidence: one study reported 12 malignant tumors in a group of 50 rats fed asbestos-containing filter material. A National Academy of Sciences review reported that four other studies showed no increased cancer, and it considered the matter unresolved.
  • Cited risk estimate (from ref. 66): the estimate used data on excess gastrointestinal cancer and peritoneal mesothelioma from three occupational studies. It held that ingesting 300,000 asbestos fibers per liter of water over a 70 year lifetime would result in one additional death per 100,000 people, or one per 200,000 if only gastrointestinal cancer is considered.
• The authors' conclusion: The authors suggested that sufficient reason exists for the water supply community to make controlling asbestos in all water supplies an official policy. They called for removing fibers from source water by filtration and for restricting asbestos-cement materials to situations where they do not contact corrosive water.
• Limitations the authors state:
  • The table of fiber concentrations in U.S. water supplies was a compilation of available data, not a representative sample. Some systems suspected of contamination were among the first analyzed.
  • Precision between laboratories in measuring 300,000 fibers per liter has not been validated.
  • Peritoneal mesothelioma is rare and not reported in the general population, so perhaps it should not have been included in the risk estimate.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos-Containing Material (ACM), Stomach Cancer, Esophageal Cancer, Epidemiology, Occupational Exposure.

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