Malignant mesothelioma: attributable risk of asbestos exposure

Our plain-English summary of Malignant mesothelioma: attributable risk of asbestos exposure, by R. Spirtas, E.F. Heineman, L. Bernstein, et al (Occupational and Environmental Medicine, 1994).

The study

• Authors: R. Spirtas, E.F. Heineman, L. Bernstein, G.W. Beebe, R.J. Keehn, A. Stark, B.L. Harlow, J. Benichou
• Journal: Occupational and Environmental Medicine
• Published: 1994;51(12):804-11
• Cited by: 241 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objectives: To evaluate a case-control study of malignant mesothelioma through patterns of exposure to asbestos based upon information from telephone interviews with next of kin.

Methods: Potential cases, identified from medical files and death certificates, included all people diagnosed with malignant mesothelioma and registered during 1975-1980 by the Los Angeles County Cancer Surveillance Program, the New York State Cancer Registry (excluding New York City), and 39 large Veterans Administration hospitals. Cases whose diagnosis was confirmed in a special pathology review as definite or probable mesothelioma (n = 208) were included in the analysis. Controls (n = 533) had died of other causes, excluding cancer, respiratory disease, suicide, or violence. Direct exposure to asbestos was determined from responses to three types of questions: specific queries as to any exposure to asbestos; occupational or non-vocational participation in any of nine specific activities thought to entail exposure to asbestos; and analysis of life-time work histories. Indirect exposures were assessed through residential histories and reported contact with family members exposed to asbestos.

Results: Among men with pleural mesothelioma the attributable risk (AR) for exposure to asbestos was 88% (95% confidence interval (95% CI) 76-95%). For men, the AR of peritoneal cancer was 58% (95% CI 20-89%). For women (both sites combined), the AR was 23% (95% CI 3-72%). The large differences in AR by sex are compatible with the explanations: a lower background incidence rate in women, lower exposure to asbestos, and greater misclassification among women.

Conclusions: Most of the pleural and peritoneal mesotheliomas in the men studied were attributable to exposure to asbestos. The situation in women was less definitive.

In plain English

This case-control study estimated how much malignant mesothelioma was attributable to asbestos. The 208 cases, diagnosed 1975-1980, were confirmed by expert pathology review as definite or probable mesothelioma. They came from Los Angeles County, New York State (excluding New York City) and 39 Veterans Administration hospitals, and were compared with 533 controls who had died of causes other than cancer, respiratory disease, suicide or violence. Next of kin were interviewed by telephone in 1982-1984. Exposure was judged from a direct asbestos question, nine activities such as insulation work and shipbuilding, a job-exposure matrix, and household and residential contact. Among men with pleural mesothelioma, 88% of cases (95% CI 76 to 95%) were attributable to asbestos. Among men with peritoneal mesothelioma the figure was 58% (95% CI 20 to 89%), and among women, both sites combined, 23% (95% CI 3 to 72%). Odds ratios for women were not statistically significant; female cases were few. The authors noted next-of-kin reports may have been biased. They concluded most mesotheliomas in the men studied were attributable to asbestos; in women the situation was less definitive.

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: Case-control study based on telephone interviews with next of kin, conducted 1982-1984
• Who was studied: 208 cases of pathologically confirmed definite or probable malignant mesothelioma, diagnosed 1975-1980 and identified from the Los Angeles County Cancer Surveillance Program, the New York State Cancer Registry (excluding New York City) and 39 large Veterans Administration hospitals. Of these, 183 (162 men, 21 women) were pleural or pleural and peritoneal, and 25 (21 men, 4 women) were peritoneal only. The comparison group was 533 controls who had died of causes other than cancer, respiratory disease, suicide or violence.
• Exposure: Asbestos; the article does not specify fiber type. Direct exposure was measured three ways: a yes/no question on ever being exposed to asbestos, nine activities thought to involve asbestos (for example brake lining work, insulation work, shipbuilding or shipyard work), and a job-exposure matrix based on the NIOSH National Occupational Hazard Survey. Indirect exposure was measured through cohabitants' exposure and residence within two miles of an asbestos mine or mill.
• Main results:
  • Among men with pleural mesothelioma, the attributable risk for asbestos exposure was 88% (95% CI 76 to 95%).
  • Among men with peritoneal mesothelioma, the attributable risk was 58% (95% CI 20 to 89%).
  • Among women (pleural and peritoneal combined), the attributable risk was 23% (95% CI 3 to 72%).
  • No known source of asbestos exposure was reported for 22 cases (11%) and 198 controls (37%).
  • None of the odds ratios among women was significantly different from 1, but there were few female cases.
  • Among men, pleural mesothelioma was more strongly associated with asbestos exposure than peritoneal mesothelioma was.
  • Of men with pleural mesothelioma, 70-80% were judged to have still been exposed in the 1950s and later, by each measure of exposure.
• The authors' conclusion: The authors concluded that nearly 90% of pleural mesothelioma among the men studied was attributable to past asbestos exposure, and perhaps 60% of peritoneal cases in men. About 20% of cases in women were attributable to asbestos, and the authors described the situation in women as less definitive.
• Limitations the authors state:
  • Next of kin of cases may have over-reported asbestos exposure on the ever-exposed question, which would make odds ratios and attributable risks artificially high.
  • The job-exposure matrix, based on 1972-74 surveys, seemed not to capture all exposures in the 1940s to 1960s.
  • Including people with little or no real exposure in the exposed groups would bias risk estimates toward the null.
  • Next of kin could not be expected to recall all of the subject's jobs and exposures.
  • The study had limited power to assess risk by age at first exposure.
  • The attributable risks are not considered directly representative of the whole US population.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma, Peritoneal mesothelioma.

Medical terms in this study, explained in our Lexicon: Malignant Mesothelioma, Attributable Risk, Asbestos Exposure, Case-Control Study, Death Certificate, Cancer Registry, Pathology Review, Mesothelioma.

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