Relative risk of mesothelioma associated with different levels of exposure to asbestos

Our plain-English summary of Relative risk of mesothelioma associated with different levels of exposure to asbestos, by T. Tuomi, M.S. Huuskonen, M. Virtamo, et al (Scandinavian Journal of Work, Environment & Health, 1991).

The study

• Authors: T. Tuomi, M.S. Huuskonen, M. Virtamo, A. Tossavainen, L. Tammilehto, K. Mattson, A. Lahdensuo, J. Mattila, P. Karhunen, K. Liippo
• Journal: Scandinavian Journal of Work, Environment & Health
• Published: 1991;17(6):404-8
• Cited by: 64 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 004449).

Abstract

The relative risk of mesothelioma associated with different levels of exposure to asbestos was evaluated. The exposure was assessed from work histories of 51 mesothelioma cases and 51 sarcoidosis referents. The lung fiber concentration of the mesothelioma patients was compared with that of two reference groups (13 random autopsy cases and 43 male lung cancer patients). When the categories definite and probable were used as an estimated probability of occupational exposure, an odds ratio of 17.7 [90% confidence interval (90% CI) 3.4-253] and 3.0 (90% CI 0.9-10.6), respectively, was obtained. A lung fiber concentration of greater than 1 million fibers/g of dry tissue as an indicator of accumulated exposure gave an odds ratio of 14.4 (90% CI 2.5-178) for the men in comparison with the autopsy cases and 3.1 (90% CI, 1.3-7.5) in comparison with the lung cancer patients. Elevated risk of mesothelioma was shown to be associated with a lung fiber concentration of greater than 1 million fibers/g of dry tissue.

In plain English

This Finnish study estimated mesothelioma risk from occupational asbestos exposure. It included 57 mesothelioma patients (43 men, 14 women) from three university hospitals in 1985–1988. Work histories of 51 patients were compared with 51 age- and gender-matched sarcoidosis patients; a panel rated exposure probability. Lung fiber counts from 31 men with mesothelioma were compared with 13 men autopsied in 1984 and 43 male lung cancer patients. Nine mesothelioma patients (18%) and no referents had definite exposure. Odds ratios were 17.7 (90% confidence interval 3.4 to 253) for definite and 3.0 (0.9 to 10.6, not statistically significant) for probable exposure. For men, more than 1 million fibers per gram of dry lung tissue gave an odds ratio of 14.4 (2.5 to 178) against autopsy cases and 3.1 (1.3 to 7.5) against lung cancer patients. Lung analysis classed 22 of 36 analyzed patients (61%) as exposed; work histories showed at least probable exposure in 19 of 51 (37%). The authors concluded that lung fiber burden better predicts risk and that the results did not support a threshold.

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-referent (case-control) study using work-history interviews, with mesothelioma cases matched to sarcoidosis referents. It was combined with a comparison of lung tissue fiber concentrations against other reference groups.
• Who was studied: 57 patients with confirmed mesothelioma (43 men, 14 women; 3 of the tumors peritoneal) from the Departments of Pulmonary Medicine at the university central hospitals of Helsinki (43), Tampere (8) and Turku (6), Finland, 1985–1988. Of these, 51 were interviewed and matched to 51 sarcoidosis referents by gender and age. Lung tissue was analyzed for 36 patients (31 men, 5 women): 30 of the interviewed patients plus 6 without interview data. The lung fiber reference groups were 13 men autopsied in 1984 and 43 male lung cancer patients.
• Exposure: Occupational asbestos exposure was assessed in two ways. First, from work histories, which a blinded panel classified as definite, probable, possible or unlikely, with one month as the minimum exposure time. Second, from lung fiber concentrations measured by scanning and transmission electron microscopy, using more than 1 million and more than 10 million fibers per gram of dry tissue as indicators. The article does not report results by fiber type.
• Main results:
  • Nine mesothelioma patients (18%) and none of the sarcoidosis referents had worked in occupations with definite asbestos exposure.
  • Of the 51 interviewed patients, 37% of the mesothelioma patients (51% of the men) and 20% of the sarcoidosis patients (27% of the men) had worked in occupations with at least probable exposure.
  • Compared with the sarcoidosis referents, the odds ratio for definite exposure was 17.7 (90% CI 3.4 to 253) and was statistically significant. For probable exposure it was 3.0 (90% CI 0.9 to 10.6), which was elevated but not statistically significant.
  • No evidence of elevated risk was found for the possible-exposure class (odds ratio 1.0).
  • Of the 36 mesothelioma patients with lung tissue analyzed, 61% (22 patients) had more than 1 million fibers per gram of dry tissue and 42% had more than 10 million.
  • All five women analyzed had below 1 million fibers per gram of dry tissue by scanning electron microscopy. Two of them had between 3 and 5 million by transmission electron microscopy.
  • For men, a lung fiber concentration above 1 million fibers per gram of dry tissue gave an odds ratio of 14.4 (90% CI 2.5 to 178) compared with the autopsy cases. Compared with the male lung cancer patients, the odds ratio was 3.1 (90% CI 1.3 to 7.5).
  • Compared with the male lung cancer patients, the odds ratio roughly doubled (to 7.2) when more than 10 million fibers per gram of dry tissue was used as the indicator.
  • The groups differed in size. Lung tissue analysis classed 61% of the 36 analyzed mesothelioma patients as exposed. Work histories of the 51 interviewed patients showed at least probable exposure for 37% in the results section; the discussion gives this figure as 38%.
  • For the 28 mesothelioma patients with at least possible exposure, the mean time from the start of asbestos-exposed work to diagnosis was 35 years (range 21 to 55).
  • Only one of the 14 female mesothelioma patients and one female sarcoidosis patient were assessed as having had possible exposure. For the rest, exposure was unlikely.
• The authors' conclusion: The authors concluded that lung fiber analysis usually gives a better and more reliable estimate of past asbestos exposure than a work history, even a thorough one, and that lung fiber burden is a better predictor of risk. They also stated that the results do not support the existence of a threshold concentration or exposure to asbestos in causing mesothelioma.
• Limitations the authors state:
  • The authors did not try to measure the intensity of exposure from work histories. They estimated only the probability of exposure lasting more than one month.
  • Assessing exposure, especially in construction work, was often difficult because work histories lacked reliable information.
  • No lung fiber data were available for the sarcoidosis referents, so other groups were used as references for the fiber comparisons.
  • The numbers of referents in the lung fiber comparisons were small.

Topics

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

Medical terms in this study, explained in our Lexicon: Relative Risk, Mesothelioma, Autopsy, Lung Cancer, Occupational Exposure, Odds Ratio, confidence interval.

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