Contribution of environmental fibers to respiratory cancer

Our plain-English summary of Contribution of environmental fibers to respiratory cancer, by G.S. Omenn, J. Merchant, E. Boatman, et al (Environmental Health Perspectives, 1986).

The study

• Authors: G.S. Omenn, J. Merchant, E. Boatman, J.M. Dement, M. Kuschner, W. Nicholson, J. Peto, L. Rosenstock
• Journal: Environmental Health Perspectives
• Published: 1986;70:51-6
• Cited by: 34 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. 000428).

Abstract

This article reviews studies of the carcinogenicity of mineral fibers, notably asbestos, and presents seven major recommendations for further research. Mineral fibers represent the greatest cause--after cigarette smoke--of respiratory cancer due to air pollutants. Past asbestos exposure may currently account for 2000 mesothelioma deaths per year and 4000 to 6000 lung cancer deaths per year. All major commercial types of asbestos (crocidolite, amosite, and chrysotile) can cause each of the major asbestos-related respiratory diseases. Lung cancers in asbestos-exposed individuals probably do not have a different distribution of histological types from that of non-asbestos-related lung cancers. Nonoccupational exposures are likely to be associated with malignant disease outcomes qualitatively similar to those associated with occupational exposures. Further investigations of fibers are needed to characterize the relationships among physicochemical properties, patterns of migration and clearance, dose, and adverse health effects. Transmission electron microscopy has been found to be the preferred method of analysis of environmental fibers. Relations among time factors (e.g., age at first exposure), dose, and risk for adverse health effects require analyses of existing and new epidemiologic studies of exposed cohorts. Concomitant exposure, behavioral factors, and host factors affecting susceptibility to asbestos should be identified.

In plain English

This article was a review, not a new study. The authors summarized government reports and other studies on cancer from mineral fibers, mainly asbestos, and made seven research recommendations. Citing an earlier estimate, they wrote that past asbestos exposure may account for about 2000 mesothelioma deaths and 4000 to 6000 lung cancer deaths per year. They reported the reviewed conclusion that crocidolite, amosite and chrysotile can all cause each major asbestos-related respiratory disease. Chrysotile may be less likely to cause pleural mesothelioma and seems not to be associated with peritoneal mesothelioma. From 11 studies of textile, product manufacturing and insulation workers, the authors reported an average lung cancer risk value, called KL, of 0.01. KL is the fractional increase in lung cancer per fiber per millilitre-year of cumulative exposure. Data from chrysotile mining suggested a value about one-tenth as large. Using a KL of 0.01, the authors estimated fewer than 100 lung cancers and 100 mesotheliomas per year in the general population from past ambient exposures. They noted great uncertainty in these estimates. They recommended more epidemiologic studies, animal and laboratory tests, and transmission electron microscopy for measuring environmental fibers.

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 of published reports and studies, with seven research recommendations; no new study population
• Who was studied: No study population of its own. The authors drew on recent major reports to the governments of the United States, Great Britain and Canada, and on studies of asbestos-exposed worker cohorts.
• Exposure: Mineral fibers, notably asbestos (crocidolite, amosite, chrysotile), and other natural and man-made fibers. Settings covered were occupational, nonoccupational, ambient air and buildings.
• Main results:
  • Citing an earlier publication (reference 1), the authors stated that past asbestos exposures may currently account for approximately 2000 mesothelioma deaths per year and 4000 to 6000 lung cancer deaths per year.
  • A key conclusion from the reviewed reports: crocidolite, amosite and chrysotile all can cause each of the major asbestos-related respiratory diseases.
  • Chrysotile may be less likely than the other types to cause pleural mesothelioma and seems not to be associated with peritoneal mesothelioma.
  • Lung cancers in asbestos-exposed individuals probably do not have a different distribution of histological types from non-asbestos-related lung cancers.
  • Nonoccupational asbestos exposures are likely to be associated with malignant disease outcomes qualitatively similar to those from occupational exposures.
  • There are no recorded cases of asbestosis from low-level nonoccupational exposure. The authors said this would be consistent with a threshold below which fibrosis may not occur.
  • KL is the fractional increase in lung cancer per fiber per millilitre-year of exposure.
  • Evaluation of 11 studies of workers in textile production, asbestos product manufacturing and insulation application suggested an average KL of 0.01. The figures summarizing these data are credited to unpublished data of W. J. Nicholson.
  • Dose-response data in chrysotile mining suggested a significantly lower KL, one-tenth of that value.
  • Mesothelioma was described by an absolute risk model. In this model, risk of death per person-year increases as about the fourth power of time from onset of exposure.
  • The ratio of pleural mesothelioma risk to excess lung cancer risk may be two to three times greater in pure crocidolite exposures.
  • In animal injection and implantation studies, fiber length and diameter appeared to be the most important factors in carcinogenic potency, rather than surface chemistry or mineral structure.
  • A 1983 U.S. EPA study covered 25 schools (116 samples). It found that airborne asbestos levels in school buildings with asbestos (about 0.009 fiber per cm3) were significantly higher than outdoor ambient levels (about 0.0003 fiber per cm3).
  • Using the lung cancer model with KL of 0.01, the authors suggested that fewer than 100 lung cancers and 100 mesotheliomas per year develop in the general population from past ambient exposures.
• The authors' conclusion: The authors made seven recommendations: (1) more epidemiologic studies; (2) priority for preventing respiratory cancer in high-risk asbestos-exposed cohorts; (3) continued animal instillation and inhalation studies; (4) development of in vitro predictive tests; (5) transmission electron microscopy as the preferred method for environmental fibers; (6) a standardized TEM method; and (7) a systematic survey of airborne asbestos in schools and other buildings.
• Limitations the authors state:
  • The authors stated there is great uncertainty in KL estimates. Causes include uncertain exposure estimates, limited numbers of deaths, and biases in the studies.
  • Mesothelioma risk estimates, especially at low exposures and over long periods, are more uncertain than those for lung cancer.
  • The contribution of building exposures to lung cancer could not be estimated without more data.
  • Economic, legal and social issues of causation and attributable risk were outside the article's scope.

Topics

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

Medical terms in this study, explained in our Lexicon: Mineral Fiber, Asbestos Exposure, Mesothelioma, Lung Cancer, Crocidolite, Amosite, Chrysotile, Occupational Exposure.

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• Host and environmental factors enhancing carcinogenesis in the respiratory tract — P. Nettesheim, D.C. Topping, et al. (1981)
• Mesothelioma associated with use of drywall joint compound: a case series and review of literature — J. Dahlgren, T. Peckham (2012)
• Man-made vitreous fibers and risk of respiratory system cancer: a review of the epidemiologic evidence — I.M. Lee, C.H. Hennekens, et al. (1995)
• Systematic review and meta-analysis of epidemiological literature evaluating the association between exposure to man-made vitreous fibers and respiratory tract cancers — N. Suder Egnot, S.M. Benson, et al. (2020)
• Respiratory cancer incidence in Swedish construction workers exposed to man-made mineral fibres and asbestos — G. Engholm, A. Englund, et al. (1987)

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