Rapporteur's Report Session 5: assessment of health risk associated with exposure to non-asbestiform amphiboles including ingestion studies

Our plain-English summary of Rapporteur's Report Session 5: assessment of health risk associated with exposure to non-asbestiform amphiboles including ingestion studies, by B. Price (Regulatory Toxicology and Pharmacology, 2008).

The study

• Author: B. Price
• Journal: Regulatory Toxicology and Pharmacology
• Published: 2008;52(1 Suppl):S204-6
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher

In plain English

This rapporteur's report summarized four review papers presented in Session 5. In the first, John Gamble reviewed studies of asbestos and stomach, colorectal, colon and rectal cancers. Gamble used lung cancer risk and the percentage of mesothelioma among exposed workers as stand-ins for exposure level. According to the report, Gamble found that exposure-response trends were not consistent and that associations were weak or non-existent. The author noted that a 2006 National Academy of Sciences report judged the evidence suggestive but not sufficient to infer a causal link with stomach or colorectal cancer. The other three papers reviewed non-asbestiform amphiboles (cleavage fragments). A review of grunerite-exposed miners and talc workers reported no excess lung cancer or mesothelioma. A review of animal studies found very little evidence of carcinogenicity. A review of cell studies found these minerals less potent than asbestos. The author wrote that, taken together, these reviews indicated that non-asbestiform amphiboles do not carry the same level of health risk as asbestiform amphiboles. The author also noted that a 2007 NIOSH research roadmap called for a broader understanding of cleavage fragment toxicity.

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: Rapporteur's report summarizing four review papers presented in a session (Session 5); not an original study
• Who was studied: Four papers. Paper 1 reviewed worker studies of gastrointestinal cancers. Paper 2 reviewed three worker groups: Homestake gold miners and taconite miners, both exposed to grunerite, and industrial talc workers in St. Lawrence County, NY. Paper 3 reviewed animal studies. Paper 4 reviewed cell and organ culture studies.
• Exposure: Asbestos, inhaled and ingested (Paper 1, gastrointestinal cancers). Non-asbestiform amphiboles, also called cleavage fragments, including grunerite and the non-asbestiform tremolite and anthophyllite in talc. Asbestos and non-asbestos tremolite and other amphiboles in animal studies.
• Main results:
  • Paper 1 (Gamble): using lung cancer rate ratio and percent mesothelioma as exposure surrogates, exposure-response trends for gastrointestinal cancers were not consistent and associations were weak or non-existent.
  • Paper 1, stomach cancer: Gamble reported a consistent pattern of weak associations, with a high proportion of SMRs below 1.0.
  • Paper 1, colorectal cancer: Gamble reported a consistent lack of associations and no exposure-response.
  • Paper 1, colon cancer: Gamble reported that the strength of association was consistently weak.
  • Paper 1, rectal cancer: Gamble concluded that the evidence did not support asbestos as a cause.
  • The author noted that the 2006 National Academy of Sciences report concluded the evidence was suggestive but not sufficient to infer causation for stomach or colorectal cancer.
  • Paper 2 (Gamble and Gibbs): cohorts exposed to non-asbestiform amphiboles showed results similar to the negative control groups. Both contrasted with the excess asbestos-related disease found in asbestos cohorts.
  • Paper 2: the authors concluded that non-asbestiform amphiboles do not increase the risk of lung cancer or mesothelioma.
  • Paper 3 (Addison and McConnell): very little evidence of carcinogenicity in animals exposed to mineral fragments or short fibers from normal prismatic amphibole minerals.
  • Paper 3: evidence suggested that fibers longer than 20 micrometers and less than 1 micrometer in diameter are needed to cause cancer. The authors asserted that amphibole cleavage fragments rarely if ever have these dimensions.
  • Paper 4 (Mossman): non-asbestiform minerals were less potent than asbestos fibers in a number of in vitro bioassays.
  • The author noted that NIOSH's February 2007 Roadmap revisited the cleavage fragment debate and concluded that a broader understanding of cleavage fragment toxicity is needed. This diverged from the session papers.
• The authors' conclusion: The author concluded that, taken together, the three cleavage-fragment reviews indicated that non-asbestiform amphiboles are not associated with the same level of health risk as asbestiform amphiboles, and are an unlikely cause of asbestos-related cancer.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Mesothelioma, Tremolite.

Medical terms in this study, explained in our Lexicon: Non-Asbestiform, Amphibole Group.

Related studies

• Rapporteur's Report Session 4: grunerite asbestos (amosite) and tremolite-ferroactinolite asbestos: risk of environmental mesothelioma — J.F. Gamble (2008)
• Risk of gastrointestinal cancers from inhalation and ingestion of asbestos — J. Gamble (2008)
• A review of carcinogenicity studies of asbestos and non-asbestos tremolite and other amphiboles — J. Addison, E.E. McConnell (2008)
• Rapporteur's Report Session 6: risk assessment of asbestos and other fibrous mineral particulates — R.P. Nolan, A.M. Langer (2008)
• Assessment of the pathogenic potential of asbestiform vs. nonasbestiform particulates (cleavage fragments) in in vitro (cell or organ culture) models and bioassays — B.T. Mossman (2008)
• An evaluation of the risks of lung cancer and mesothelioma from exposure to amphibole cleavage fragments — J.F. Gamble, G.W. Gibbs (2008)

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