Critical review of epidemiologic studies related to ingested asbestos

Our plain-English summary of Critical review of epidemiologic studies related to ingested asbestos, by G.M. Marsh (Environmental Health Perspectives, 1983).

The study

• Author: G.M. Marsh
• Journal: Environmental Health Perspectives
• Published: 1983;53:49-56
• Cited by: 19 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000623).

Abstract

Thirteen epidemiologic studies of ingested asbestos conducted in five areas of the United States and Canada were reviewed and evaluated for the definitiveness and applicability regarding the development of ambient water quality standards. One or more studies found male or female associations between asbestos in water supplies and cancer mortality (or incidence) due to neoplasms of the esophagus, stomach, small intestine, colon, rectum, gallbladder, pancreas, peritoneum, lungs, pleura, prostate, kidneys, brain, and thyroid, and also due to leukemia. Several methodologic weaknesses and limitations were found in each study, leading to the determination that no individual study or aggregation of studies exist that would establish risk levels from ingested asbestos. A binomial probability analysis of the eight independent studies suggested that, while the level of male-female agreement was generally low, the number of observed positive associations in males and females for neoplasms of the esophagus, stomach, pancreas, and prostate was unlikely to have been generated by chance factors alone, and thus, may have a biological basis related to ingested asbestos. Cancers of the small intestine and leukemia were implicated to a lesser degree in this analysis. The patterns of integrated findings for most gastrointestinal cancers were somewhat consistent with patterns observed among asbestos-exposed occupational groups, whereas the patterns found for pancreatic cancer, kidney cancer, and leukemia were not consistent.(ABSTRACT TRUNCATED AT 250 WORDS)

In plain English

This review, commissioned by the U.S. Environmental Protection Agency in 1982, covered 13 published and unpublished studies of cancer and asbestos in drinking water. The studies came from Duluth, Connecticut, Quebec, the San Francisco Bay Area, Utah and Puget Sound. Duluth involved amphibole fibers; the other areas, chrysotile. One or more studies had reported associations at many cancer sites. However, every study was ecologic, meaning it compared areas, not individuals, and the author said this did not permit a definitive conclusion. These studies made 33 to 336 statistical comparisons each, so some positive findings were expected by chance. The author combined eight independent studies in a probability analysis. Esophagus, stomach, pancreas, lungs and prostate had probability values below or near 0.05. For esophagus, stomach and pancreas, male-female agreement was moderate to low; it could not be measured for lungs, and prostate was studied only in men. Small intestine and leukemia were implicated less firmly. The author concluded that no study or group of studies established risk levels from ingested asbestos. The author cautioned that the probability analysis was not conclusive.

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: Critical review of epidemiologic studies, commissioned by the U.S. EPA, including a binomial probability analysis combining results across independent studies
• Who was studied: 13 published and unpublished epidemiologic studies from the United States and Canada (Duluth, Connecticut, Quebec, San Francisco Bay Area, Utah, Puget Sound); eight were treated as independent for the probability analysis
• Exposure: Asbestos in public drinking water: amphibole fibers in Lake Superior water supplying Duluth; chrysotile in the other areas (from serpentine rock, asbestos-cement pipe, or mining regions). For Utah, the study was based on use of asbestos-cement pipe, and no fiber concentration was available.
• Main results:
  • Across the 13 studies, one or more found associations in males or females between asbestos in water and cancer mortality or incidence at various sites, including the esophagus, stomach, pancreas, peritoneum, lungs, pleura, prostate and kidneys, and leukemia
  • All the studies were ecologic in design, which the author said did not permit a definitive conclusion from any of them
  • The studies reported between 33 and 336 separate statistical comparisons, with an average of 193
  • At a 5% significance level, about 2 to 17 positive findings per study would be expected by chance alone
  • In the probability analysis, five cancer sites (esophagus, stomach, pancreas, lungs, prostate) had large deviation probability values consistently below or near 0.05
  • Male-female agreement was low: positive associations in both sexes appeared in only 1 of 6 esophageal cancer studies, 2 of 8 stomach cancer studies and 1 of 8 pancreatic cancer studies
  • Male-female agreement could not be quantified for lung cancer; prostate cancer was assessed in males only
  • Small intestine cancer and leukemia/aleukemia had probability values below 0.05 using p = 0.05, but above 0.05 using the more conservative p = 0.10
  • In the two Quebec studies, positive associations for lung and stomach cancer were confined to males, which the author attributed to confounding by occupation
  • Gastrointestinal cancer findings were somewhat consistent with patterns seen in occupationally exposed workers
  • Kidney cancer was in excess among males in only one of the six independent studies that examined it
• The authors' conclusion: The author concluded that no individual study or combination of studies establishes risk levels from ingested asbestos. The author recommended testing hypotheses at the individual level (e.g., case-control studies) and judged the Bay Area and Puget Sound the most suitable areas for this.
• Limitations the authors state:
  • The author stated that the probability analysis results should not be regarded as conclusive
  • The probability analysis was limited by very small sample size and by having to assume the studies provided equivalent information
  • The positive, negative or no-association judgments were subjective and were not always the original study authors' interpretations

Topics

Medical terms in this study, explained in our Lexicon: Neoplasm, Peritoneum, Pleura.

Related studies

• Additional thoughts on the review of epidemiologic studies related to ingested asbestos — G.M. Marsh (1983)
• Comparing epidemiologic studies of ingested asbestos for use in risk assessment — L.S. Erdreich (1983)
• Health implications of environmental exposure to asbestos — J.C. McDonald (1985)
• Relative source contributions of diet and air to ingested asbestos exposure — J.N. Rowe (1983)
• Cancer incidence in relation to asbestos in drinking water in the Puget Sound region — L. Polissar, R.K. Severson, et al. (1982)
• The epidemiologic evidence for elongate mineral particle (EMP)-related human cancer risk — P. Boffetta, K.A. Mundt, et al. (2018)

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