Report on cancer risks associated with the ingestion of asbestos. DHHS Committee to Coordinate Environmental and Related Programs

Our plain-English summary of Report on cancer risks associated with the ingestion of asbestos. DHHS Committee to Coordinate Environmental and Related Programs (Environmental Health Perspectives, 1987).

The study

• Journal: Environmental Health Perspectives
• Published: 1987;72:253-65
• Type of article: Review
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

This report is an assessment of all available literature that pertains to the potential risk of cancer associated with ingestion of asbestos. It was compiled by a working group to assist policy makers in the Department of Health and Human Services determine if adequate information was available for a definitive risk assessment on this potential problem and evaluate if the weight of evidence was sufficient to prioritize this issue for new policy recommendations. The work group considered the basis for concern over this problem, the body of toxicology experiments, the individual epidemiologic studies which have attempted to investigate this issue, and the articles that discuss components of risk assessment pertaining to the ingestion of asbestos. In the report, the work group concluded: that no direct, definitive risk assessment can be conducted at this time; that further epidemiologic investigations will be very costly and only possess sufficient statistical power to detect relatively large excesses in cancers related to asbestos ingestion; and that probably the most pertinent toxicologic experiments relate to resolving the differences in how inhaled asbestos, which is eventually swallowed, is biologically processed by humans, compared to how ingested asbestos is processed. The work group believes that the cancer risk associated with asbestos ingestion should not be perceived as one of the most pressing potential public health hazards facing the nation. However, the work group does not believe that information was sufficient to assess the level of cancer risk associated with the ingestion and therefore, this potential hazard should not be discounted, and ingestion exposure to asbestos should be eliminated whenever possible.

In plain English

This was a review by a U.S. Department of Health and Human Services working group. It asked whether swallowing asbestos in water, food, beverages or drugs may cause cancer. It covered 11 animal studies of asbestos ingestion and human studies from seven U.S. and Canadian areas. Two lifetime National Toxicology Program studies found no cancer response in hamsters fed 1% amosite or chrysotile, or rats fed 1% amosite or tremolite. A third found a marginally significant increase in benign intestinal growths (adenomatous polyps) in male rats fed 1% intermediate-length chrysotile (65% of fibers over 10 micrometers). The authors cautioned this may not apply to all ingested asbestos. All but one human study compared areas, not individuals. Of these, only a San Francisco Bay Area study linked waterborne asbestos to area cancer rates. The one case-control study found no definitive excess; none gave useful dose-response data. The authors concluded that direct evidence was insufficient for a credible quantitative risk assessment, and any association probably weak. They did not rank it among the nation's most pressing hazards but said it should not be dismissed.

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 (working group assessment of the available toxicologic and epidemiologic literature on cancer risk from ingested asbestos)
• Who was studied: Published studies: 11 animal toxicology studies of asbestos ingestion, and epidemiologic studies of drinking water and cancer in seven areas of the United States and Canada (Duluth, Minnesota; Connecticut; Quebec; San Francisco Bay Area; Utah; Puget Sound, Washington; Escambia County, Florida)
• Exposure: Ingested asbestos, mainly in drinking water (from asbestos cement pipe, cistern run-off from asbestos cement shingle roofs, dumping, and natural sources) and also in food, beverages and pharmaceuticals from asbestos filters. The fiber was amphibole in Duluth and chrysotile in the other areas. In the National Toxicology Program studies, animals were fed diets of 1% asbestos: amosite or chrysotile for hamsters; amosite, tremolite or chrysotile for rats.
• Main results:
  • Two lifetime National Toxicology Program studies showed no carcinogenic response in Syrian golden hamsters fed 1% amosite or chrysotile, or in F344 rats fed 1% amosite or tremolite.
  • A third National Toxicology Program study found a marginally significant increase in adenomatous polyps in male F344 rats fed 1% chrysotile of intermediate length (65% of fibers longer than 10 micrometers) for their lifetime. The working group described this as some evidence of weak tumorigenicity.
  • All but one of the epidemiologic studies were ecological (area-level). Of these, only the Kanarek et al. San Francisco Bay Area study showed an association between area cancer rates and asbestos in drinking water.
  • The only non-ecological study, a case-control study in Everett, Washington, did not show a definitive excess of cancer associated with asbestos in drinking water.
  • None of the epidemiologic studies gave useful dose-response information, so they could not support a quantitative risk assessment.
  • Weighing the epidemiologic data, the working group judged that if an association exists, it is probably weak relative to background cancer rates.
• The authors' conclusion: The authors concluded that sufficient direct evidence was not available for a credible quantitative cancer risk assessment of asbestos ingestion. They did not consider the risk among the most pressing U.S. environmental health hazards, but said it should not be taken as unimportant. Several working group members believed it prudent to eliminate ingestion exposure where possible, and the report states this is not a DHHS recommendation.
• Limitations the authors state:
  • Almost all available human studies were ecological or geographic correlation studies, and they were too small to detect modest increases in risk.
  • Exposure misclassification arose from four sources: assigning one exposure level to a whole area, assumptions about contamination from asbestos cement pipe, lack of reliable historical exposure data, and population mobility.
  • Using the animal results for human risk requires uncertain extrapolations: between species, and from high bioassay doses to ambient human doses.
  • The authors stated that it may be a mistake to use the results from intermediate-length chrysotile for risk estimation for all types of ingested asbestos.

Related studies

• Risks of environmental exposure to asbestos — (1978)
• Malignant peritoneal mesothelioma in a 76-year-old woman with a history of asbestos fiber ingestion — P. Van Kesteren, J. Bulten, et al. (2004)
• Time-related factors in quantitative risk assessment — K.S. Crump, B.C. Allen, et al. (1987)
• Critical review of epidemiologic studies related to ingested asbestos — G.M. Marsh (1983)
• Additional thoughts on the review of epidemiologic studies related to ingested asbestos — G.M. Marsh (1983)
• A case-control study of asbestos in drinking water and cancer risk — L. Polissar, R.K. Severson, et al. (1984)

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