Mortality among asbestos-exposed workers in a railroad workshop

Our plain-English summary of Mortality among asbestos-exposed workers in a railroad workshop, by C.G. Ohlson, B. Klaesson, C. Hogstedt (Scandinavian Journal of Work, Environment & Health, 1984).

The study

• Authors: C.G. Ohlson, B. Klaesson, C. Hogstedt
• Journal: Scandinavian Journal of Work, Environment & Health
• Published: 1984;10(5):283-91
• Cited by: 36 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. 000564).

Abstract

The mortality experience of a cohort of 3 297 railroad maintenance shopworkers exposed to asbestos was investigated. The study period was 1951-1980, and the vital status was assessed for 99.6% of the men. Individual estimates of cumulative asbestos exposure were based on detailed records on work tasks and divisions. Dust measurements were scanty in earlier decades, and estimates of average fiber levels were therefore based on information on the amount and kind of asbestos used, job descriptions, and interviews with older workers. The overall mortality was lower than expected from the national death rates (standardized mortality ratio = 82). The mortality from lung cancer increased as cumulative exposure increased in consistent dose-response relationships. Employment times of less than 30 years in workplaces with moderate levels of mainly chrysotile asbestos was not associated with any apparent increase in the risk of lung cancer. A subgroup exposed for more than 30 years in workplaces repairing steam engines, where amphiboles were used as well, had a standardized mortality ratio of 192 for lung cancer. This figure may be an underestimation due to healthy worker selection and fewer smokers than normal. The "true" standardized mortality ratio was estimated to be about 300. Five cases of mesothelioma were observed.

In plain English

This Swedish cohort study examined deaths among men from a railroad maintenance workshop. Of 3,442 men hired in 1939 to 1980, 3,297 were followed for deaths in 1951 to 1980. Exposure was estimated from work records and recollections because dust measurements were scanty. Insulation contained crocidolite, chrysotile and amosite. Overall mortality was below national rates (SMR 82), while lung cancer mortality was raised (SMR 116). Lung cancer SMRs rose with cumulative exposure, from 27 to 162. For men who ever worked in steam-engine repair divisions and had at least 30 years' total employment, the lung cancer SMR was 192. Five mesotheliomas occurred, three in men with recorded amphibole exposure. Allowing for the cohort's low baseline risk, the authors estimated that the highest exposure category's true lung cancer risk may have been at least threefold that of nonexposed workers. Men employed under 30 years without the highest dust intensities had no apparent increase in lung cancer risk. Individual smoking histories were unavailable, and the authors cautioned that more cancers may appear with further follow-up.

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: Retrospective cohort mortality study comparing observed deaths with expected numbers from Swedish national death rates (standardized mortality ratios)
• Who was studied: Men hired for three weeks or longer in 1939 to 1980 at a Swedish railroad workshop that repaired and maintained engines, railcars, passenger coaches and rail switches. There were 3,442 men in total. Vital status was assessed for 99.6%, the remaining 14 were excluded, and 3,297 were analyzed. Deaths were studied over 1951 to 1980.
• Exposure: The exposure was asbestos insulation work, mainly on steam engines and passenger coaches. Crocidolite-filled insulation mattresses were used in the 1920s and 1930s, and the mattresses were filled with chrysotile during the Second World War. 'Magnesia lagging' was probably a mixture of amosite and magnesia. Passenger coaches were spray-insulated with crocidolite in 1961 to 1971, and chrysotile yarns and amosite were also used. Exposure intensity was graded on a dust score from 0 to 4, and the heaviest exposure (score 4) was estimated at 10 to 20 fibers/ml. Cumulative exposure was calculated as score multiplied by years.
• Main results:
  • Overall mortality for the whole cohort was lower than expected from national death rates: SMR 82.
  • Lung cancer mortality for the whole cohort was increased: SMR 116. Mortality from chronic obstructive lung disease was low: SMR 36.
  • Men employed 30 years or more had a lung cancer SMR of 154.
  • By cumulative exposure (score multiplied by years), the lung cancer SMR increased from 27 in the lowest category to 162 in the highest.
  • By number of years in heavily exposed work, the lung cancer SMR increased from 47 to 189 in the highest category (p = 0.05, 95% confidence interval 1.00 to 3.22).
  • Men employed before 1939 had a lung cancer SMR of 188 (p less than 0.05).
  • The highest lung cancer relative risk was in men who had been employed in divisions where steam engines were repaired and who had a total employment time of at least 30 years: SMR 192.
  • Men employed for less than 30 years and without exposure to the highest dust intensities had no apparent increase in lung cancer risk.
  • Five mesotheliomas were observed, and they were not counted among the lung cancers. Three of the five men had recorded amphibole exposure from steam engine insulation. The cases had an average age at death of 76 (range 70 to 82), an average latency of 44 years (range 30 to 57) and an average employment time of 32 years (range 26 to 37).
  • Men employed 15 to 30 years showed a weak increase in pancreas cancer deaths. This increase was not related to the degree or length of exposure, and the authors considered a causal association less likely.
• The authors' conclusion: The authors concluded that lung cancer mortality was moderately increased, with a dose-response relationship to asbestos exposure. Allowing for the cohort's low baseline risk, they estimated that the true lung cancer risk in the highest exposure category may have been at least threefold that of nonexposed workers. They also concluded that after the Second World War, employment at the workshop other than steam engine repairing was not associated with any apparent increase in lung cancer risk.
• Limitations the authors state:
  • Good health was required for employment, which together with the healthy worker effect limits the usefulness of national death rates as a comparison. No other comparison group was available.
  • Smoking habits of individual workers were not available. In a sample of workers examined at the end of the 1970s, 36% had never smoked, and low chronic obstructive lung disease mortality was used as an indirect sign of fewer smokers.
  • Dust measurements were scanty in earlier decades, so fiber levels had to be estimated indirectly.
  • The effect of different fiber types could not be studied in detail because of mixed exposures and lack of historical information.
  • Because of long latency periods, more asbestos-related cancers may appear with further follow-up, so the conclusions should be interpreted with care.

Topics

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

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, standardized mortality ratio (SMR), Lung Cancer, Cumulative Exposure, Dose-response relationship, Chrysotile, Amphibole Group, Mesothelioma.

Related studies

• A case-control study of lung cancer and diesel exhaust exposure in railroad workers — E. Garshick, M.B. Schenker, et al. (1987)
• Asbestos-related disease in railroad workers. A cross-sectional study — L.C. Oliver, E.A. Eisen, et al. (1985)
• Roentgenographic evidence of asbestos exposure in a select population of railroad workers — M.J. Sepulveda, J.A. Merchant (1983)
• Asbestos-related mesothelioma risk among railroad workers — M. Huncharek (1987)
• A retrospective cohort study of lung cancer and diesel exhaust exposure in railroad workers — E. Garshick, M.B. Schenker, et al. (1988)
• Railroad workers with pleural plaques: I. Spirometric and nitrogen washout investigation on smoking and nonsmoking asbestos-exposed workers — U. Hjortsberg, P. Orbaek, et al. (1988)

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