Is chrysotile a significant risk factor for mesothelioma?

Our plain-English summary of Is chrysotile a significant risk factor for mesothelioma?, by C.G. Ohlson (American Journal of Industrial Medicine, 1989).

The study

• Author: C.G. Ohlson
• Journal: American Journal of Industrial Medicine
• Published: 1989;15(3):351-6
• Type of article: Comment
• Cited by: 4 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. 000140).

Summary of the article

In this letter to the editor, the author challenged the conclusion of a 1988 paper by Mancuso that chrysotile is far more hazardous in causing mesothelioma than previously estimated. Mancuso's conclusion was based on a cohort of 181 railroad machinists hired between 1920 and 1929, among whom 14 mesotheliomas were identified through 1986. The author made two comments. First, he questioned the statement that the machinists were exposed almost exclusively to chrysotile. He noted that an earlier paper by Mancuso (1983) reported fiber analysis identifying amosite in four of six samples from old locomotives. He also described a Swedish railroad maintenance shop where padded insulation containing crocidolite was used on steam boiler funnels, and where magnesia lagging containing chrysotile, and probably amosite, was also used. In that Swedish cohort of 3,297 male workers, studied from 1951 to 1980, only five mesotheliomas were observed. The author argued that even small amounts of amphiboles could explain the mesotheliomas, because amphiboles are highly durable in the lungs and chrysotile is not. Second, he noted that the machinists were still employed two decades after 1920-29 and may have had further decades of exposure. The average latent period was 48 years (33-64) for the mesotheliomas and 40 years (27-51) for lung cancers, which he considered longer than generally agreed. He concluded that Mancuso's data did not support the claim that chrysotile poses a considerable mesothelioma risk.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.

In plain English

This was a letter to the editor, not a new study. The author responded to a 1988 paper by Mancuso. That paper had concluded that chrysotile is far more hazardous in causing mesothelioma than previously estimated, based on 14 mesotheliomas found through 1986 among 181 railroad machinists hired between 1920 and 1929. The author questioned the claim that the machinists were exposed almost only to chrysotile. An earlier Mancuso paper had reported amosite in four of six samples from old locomotives. A Swedish railroad shop, studied earlier by the author and colleagues, used insulation containing crocidolite, and in that study five mesotheliomas were seen among 3,297 male workers whose deaths were followed up to 1980. The author argued that small amounts of amphiboles could explain the mesotheliomas. The machinists may also have had decades of further exposure after the 1920s. Their average mesothelioma latent period of 48 years (range 33 to 64) was much longer than generally agreed. The author concluded that Mancuso's data did not support the statement that chrysotile poses a considerable mesothelioma risk.

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: Letter to the editor commenting on another author's published study (Mancuso, 1988); no new data were collected
• Who was studied: No study population of its own. The letter discussed Mancuso's cohort of 181 railroad machinists hired between 1920 and 1929. It also cited the author's own earlier study (Ohlson et al., 1984) of the mortality of 3,297 male workers at a Swedish railroad maintenance shop, over a period ending in 1980. The start year is garbled in the scanned text.
• Exposure: Asbestos exposure of railroad machinists. Mancuso described it as almost entirely chrysotile. The author argued that it included amphiboles (amosite) and continued for decades after 1920-1929, mainly chrysotile but apparently amphiboles as well.
• Main results:
  • As reported in the Mancuso study under discussion, 14 mesotheliomas were identified through 1986 among the 181 machinists.
  • The author pointed out that an earlier Mancuso paper (1983) reported a fiber analysis that found amosite in four of six samples from old locomotives.
  • In the author's earlier Swedish study, padded insulation containing crocidolite was used in the railroad shop. Only five mesotheliomas were observed among the 3,297 male workers.
  • The author argued that even small amounts of amphiboles would have been enough to explain the mesotheliomas, because amphiboles are highly durable in the lungs and chrysotile is not.
  • In Mancuso's cohort, the average latent period (first exposure to death) was 48 years (range 33-64) for the 14 mesothelioma cases and 40 years (27-51) for the lung cancer cases. The author said these were much longer than generally agreed latent periods.
  • The author noted that the machinists were still employed two decades after 1920-1929 and could have had several decades of further high asbestos exposure.
• The authors' conclusion: In the author's view, the data in Mancuso's paper did not support the statement that chrysotile poses a considerable risk for mesothelioma.
• Limitations the authors state:
  • The author acknowledged that work practices in US and Swedish railroad maintenance shops may have differed somewhat, though the author still considered the Swedish cohort relevant.

Topics

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

Medical terms in this study, explained in our Lexicon: Chrysotile, Mesothelioma, Amosite, Crocidolite, Amphibole Group, Lung Cancer.

Related studies

• Relative risk of mesothelioma among railroad machinists exposed to chrysotile — I. Higgins (1989)
• Relative risk of mesothelioma among railroad machinists exposed to chrysotile — T.F. Mancuso (1988)
• Asbestos-related mesothelioma risk among railroad workers — M. Huncharek (1987)
• Re: Mesothelioma in railroad machinists — A. Churg, F. Green (1990)
• Mesotheliomas due to asbestos used in railroads in Italy — C. Maltoni, C. Pinto, et al. (1991)
• Mesotheliomas following exposure to asbestos used in railroads: the Italian cases — C. Maltoni, C. Pinto, et al. (1991)

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