Asbestos ingestion and gastrointestinal cancer: a possible underestimated hazard

Our plain-English summary of Asbestos ingestion and gastrointestinal cancer: a possible underestimated hazard, by A. Di Ciaula (Expert Review of Gastroenterology & Hepatology, 2017).

The study

• Author: A. Di Ciaula
• Journal: Expert Review of Gastroenterology & Hepatology
• Published: 2017;11(5):419-425
• Type of article: Review
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The presence of asbestos fibres (AFs) in drinking water could be linked with gastrointestinal cancers. However, it is not regulated in several countries due to conflicting evidence. Areas covered: Some reports mainly associated AF ingestion with gastric and colorectal cancer. Experimental evidence suggested a role for timing and extent of exposure, and showed that ingested AFs induce toxic effects on the stomach, ileum and colon, histological alterations and negative effects at a molecular level, cross the placenta and enter foetal organs (including the liver), and seem able to act as a co-carcinogen agent. Occupational studies suggest associations between asbestos exposure and intrahepatic cholangiocarcinoma, and observations exist indicating the possibility that AFs could enter the liver and bile through enteric absorption. Expert commentary: A risk threshold (AF concentration in drinking water) for digestive cancers has not been convincingly identified so far and regulations, where adopted, have weak scientific basis and may not be adequate. With further and more definitive studies, evidence might become sufficient to justify monitoring plans, persuade countries with no current limits to set a maximum level of AFs in drinking water and might induce a revision of the existing legislations, pointing to efficient primary prevention policies.

In plain English

This was a single-author review, not a new study. It examined published evidence linking swallowed asbestos, mainly from asbestos cement water pipes and tanks, to digestive cancers. Cited rat experiments reported effects of ingested asbestos on the ileum and colon, and stomach cancers when chrysotile was placed in a bag on the stomach. The author noted that the IARC monograph cited only two negative human studies, while four others showed significant excesses of stomach cancer with drinking-water exposure. A cited Norwegian study found a standardized incidence ratio of 241 (95% confidence interval 120–431) for stomach cancer in male lighthouse keepers first exposed at least 20 years before diagnosis, a 2.4-fold excess. The author questioned the US EPA limit of 7 million fibers per litre because it counts only fibers longer than 10 µm, while over 95% of fibers from asbestos cement pipes are shorter. Only a few studies produced strong results, the author stated, and no clear risk threshold has been identified. The author concluded that the evidence appears sufficient to justify monitoring in risk areas and limits in countries that have none.

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 of published animal, human drinking-water and occupational studies (no new data collected)
• Who was studied: No study population of its own; the review covered experiments in rats and epidemiological studies of drinking-water exposure (USA, Canada, Norway) and of occupationally exposed workers
• Exposure: Ingested asbestos fibers, mainly in drinking water released from asbestos cement pipes and water tanks; animal studies used chrysotile, crocidolite and anthophyllite; occupational asbestos exposure was also discussed
• Main results:
  • A cited rat study reported that daily dietary ingestion of asbestos caused histological changes in the ileum and colon-rectum
  • In a cited rat study, chrysotile was placed in a bag on the stomach rather than ingested, and the rats developed cancer of the stomach and abdominal cavity within 25 months
  • The author noted that the IARC monograph cited only two negative human studies on ingested asbestos and gastric or colorectal cancer
  • The author reported that four other studies described in the IARC monograph showed significant excesses of gastric cancer in people exposed through drinking water, and that one study showed increased colorectal cancer incidence
  • A cited Norwegian study reported a standardized incidence ratio for gastric cancer of 241 (95% confidence interval 120–431) in male lighthouse keepers who drank asbestos-contaminated water, with a latency of 20 years or more
  • The review's table describes the same Norwegian finding as a 2.4-fold excess in those first exposed at least 20 years before diagnosis
  • The author reported that recent studies of workers linked occupational asbestos exposure with increased risk of cancers of the esophagus, stomach, liver and colon-rectum
  • A cited autopsy study of stillborn infants found asbestos fibers in the placenta, lung, muscle and liver
  • The US EPA threshold is 7 million fibers per litre and counts only fibers longer than 10 µm. The author pointed out that more than 95% of fibers from asbestos cement pipes and cisterns are shorter than 10 µm
  • Asbestos is not explicitly listed as a parameter in the EU Drinking Water Directive
• The authors' conclusion: The author concluded that the available evidence appears sufficient to justify monitoring in risk areas, should lead countries without limits to set a maximum level of asbestos in drinking water, and might justify revising existing rules
• Limitations the authors state:
  • The author stated that only a few of the studies reviewed produced strong results
  • The author stated that definitive studies identifying a risk threshold in non-occupationally exposed groups are lacking, because of long latency, other risk factors, absent monitoring and difficulty measuring individual exposure

Topics

Medical terms in this study, explained in our Lexicon: Colorectal Cancer, Asbestos Exposure.

Related studies

• Cancer of the gastrointestinal tract and exposure to asbestos in drinking water among lighthouse keepers (Norway) — K. Kjaerheim, B. Ulvestad, et al. (2005)
• Risk of gastrointestinal cancers from inhalation and ingestion of asbestos — J. Gamble (2008)
• Evaluation of potential gastrointestinal carcinogenicity associated with the ingestion of asbestos — T.J. Cheng, S.L. More, et al. (2021)
• Investigating possible effects of abestos in city water: surveillance of gastrointestinal cancer incidence in Duluth, Minnesota — B.S. Levy, E. Sigurdson, et al. (1976)
• Rapporteur's Report Session 5: assessment of health risk associated with exposure to non-asbestiform amphiboles including ingestion studies — B. Price (2008)
• Malignant peritoneal mesothelioma in a 76-year-old woman with a history of asbestos fiber ingestion — P. Van Kesteren, J. Bulten, et al. (2004)

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