Relative risk of mesothelioma among railroad machinists exposed to chrysotile

Our plain-English summary of Relative risk of mesothelioma among railroad machinists exposed to chrysotile, by T.F. Mancuso (American Journal of Industrial Medicine, 1988).

The study

• Author: T.F. Mancuso
• Journal: American Journal of Industrial Medicine
• Published: 1988;13(6):639-57
• Cited by: 38 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. 000250).

Abstract

This study challenges the assertion of low relative risk of chrysotile in the causation of mesothelioma. Data are provided on the time period use of various types of asbestos in the United States and in insulation materials. The focus of the study is on mesothelioma among railroad machinists employed in the steam locomotive era who were exposed to chrysotile. Within a cohort of machinists alive January 1, 1945, a sub-cohort method was applied to all successive machinists hired in each of the respective years (1920-1929) followed through 1986. The total cohort was 181 and the number of deaths 156, with 14 mesotheliomas identified among 41 cancer deaths. The findings demonstrated an extremely high relative risk for machinists exposed to chrysotile for the induction of mesothelioma in the individual year of hire cohorts. A similar observation was noted for other crafts hired in the same time period. One mesothelioma occurred for every 13 machinists hired in the succeeding years (1920-1929) and constituted 34% of all cancer deaths. It is concluded that chrysotile is far more hazardous in the induction of mesotheliomas and that the asbestos cancer risk in the steam locomotive eras was much higher than had been previously estimated.

In plain English

This was a mortality study of white male railroad machinists at an unnamed company ("company A"). From a seniority list of men alive on January 1, 1945, the author followed the 181 machinists hired from 1920 to 1929 through 1986. Deaths were identified from union death claim records. The author concluded from historical sources that the boiler lagging was almost exclusively, if not solely, chrysotile. By 1986, 156 had died. Of 41 cancer deaths, 14 were mesotheliomas; 11 of the 36 identified primary cancers were lung cancers, with one man counted in both groups. Mesotheliomas occurred in every hire year except 1921 and 1928, when only 9 men and 1 man were hired. The author called this a relative risk of one mesothelioma per 13 machinists hired. Two of the 14 boilermaker helpers hired in 1925 also died of mesothelioma. The author concluded that chrysotile is far more hazardous in the induction of mesotheliomas, and that the asbestos cancer risk in the steam locomotive era was much higher than previously estimated. The author noted that men who left before 1945 were missed.

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: Mortality follow-up of a railroad seniority-list cohort, split into successive year-of-hire sub-cohorts that the author used for internal comparison
• Who was studied: 181 white male machinists at railroad company A who were hired 1920-1929 and were alive and employed in 1945, followed through 1986. The full 1945 cohort, hired before 1935, numbered 285.
• Exposure: Asbestos in the lagging insulation of steam locomotive boilers. The author inferred from historical consumption and usage data that this was almost exclusively, if not solely, chrysotile. Exposure was not measured for these workers.
• Main results:
  • Among the 156 deaths in machinists hired 1920-1929 there were 41 cancer deaths with 36 identified primary sites. 14 were mesotheliomas, which the text gives as 35% of all cancers.
  • There was one mesothelioma death for every 11 deaths, or one mesothelioma for every 13 of the 181 machinists hired. The author called this ratio the relative risk.
  • Mesothelioma occurred in each year-of-hire group from 1920 to 1929 except 1921 and 1928, when only 9 men and 1 man were hired.
  • There were 11 lung cancer deaths among the 36 primary cancer deaths, compared with 14 mesotheliomas.
  • One machinist hired in 1922 had a diagnosed pleural mesothelioma, but his death certificate listed lung cancer. He was counted in both categories.
  • 12 of the 14 machinists with mesothelioma died at age 65 or over.
  • Among other crafts, 2 of the 14 boilermaker helpers hired in 1925 died of mesothelioma.
• The authors' conclusion: The author concluded that chrysotile is far more hazardous in the induction of mesotheliomas, and that the asbestos cancer risk in the steam locomotive era was much higher than had been previously estimated.
• Limitations the authors state:
  • The 1945 seniority list is a survivor group. Machinists who left or retired before 1945 were not included.
  • Other mesotheliomas may have occurred among machinists who retired or left before 1945.
  • Some lung cancers may not have been recorded on death certificates.

Topics

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

Medical terms in this study, explained in our Lexicon: Relative Risk, Mesothelioma, Chrysotile, Causation.

Related studies

• Relative risk of mesothelioma among railroad machinists exposed to chrysotile — I. Higgins (1989)
• Mesothelioma among machinists in railroad and other industries — T.F. Mancuso (1983)
• Re: Mesothelioma in railroad machinists — A. Churg, F. Green (1990)
• Asbestos-related mesothelioma risk among railroad workers — M. Huncharek (1987)
• A case-control study of lung cancer and diesel exhaust exposure in railroad workers — E. Garshick, M.B. Schenker, et al. (1987)
• Mortality among asbestos-exposed workers in a railroad workshop — C.G. Ohlson, B. Klaesson, et al. (1984)

Browse more research in American Journal of Industrial Medicine, or return to medical research.