Mortality due to asbestos-related causes among railway carriage construction and repair workers

Our plain-English summary of Mortality due to asbestos-related causes among railway carriage construction and repair workers, by G. Battista, S. Belli, P. Comba, et al (Occupational Medicine, 1999).

The study

• Authors: G. Battista, S. Belli, P. Comba, C. Fiumalbi, M. Grignoli, F. Loi, D. Orsi, I. Paredes
• Journal: Occupational Medicine
• Published: 1999;49(8):536-9
• Cited by: 20 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The objective of this study was to further clarify the cancer risk associated with asbestos exposure in railway carriage construction and repair. The cohort included 734 subjects employed between 1 January 1945 and 31 December 1969. Vital status was ascertained at 31 December 1997. Mortality was investigated in the time span 1970-97. Forty-two subjects (6%) were lost to follow-up and eight causes of death (4%) could not be ascertained. The overall mortality was not above the expected value. Among neoplastic diseases, excesses were observed for lung ştandardized mortality ratio (SMR) = 124; 90% confidence interval (CI) = 87-172; 26 obs), pleura (SMR = 1,327; CI = 523-2,790; 5 obs), larynx (SMR = 240; CI = 95-505; 5 obs), liver (SMR = 241; CI = 126-420; 9 obs), pancreas (SMR = 224; CI = 98-443; 6 obs) and multiple myeloma (SMR = 429; CI = 117-1,109; 3 obs). The observed excess of lung and pleural neoplasms can be causally related to asbestos exposure in the manufacture of railway carriages. A causal role of asbestos exposure in the raised SMRs from laryngeal and pancreatic neoplasms and multiple myeloma cannot be conclusively proven.

In plain English

The authors followed 734 men hired in 1945-1969 at a railway carriage construction and repair plant, studying their deaths in 1970-1997. Carriages were insulated with chrysotile boards from the 1940s and with sprayed crocidolite-containing mixtures from the 1950s. No fibre measurements exist. Deaths were compared with expected numbers from Tuscany Region rates. Overall mortality was not above expected (199 deaths observed, 199.37 expected). Pleural cancer deaths were raised: 5 observed, standardized mortality ratio (SMR) 1,327 (90% confidence interval 523 to 2,790). Four were confirmed mesotheliomas, and two living workers also had mesothelioma. Lung cancer had an SMR of 124 (87 to 172; 26 deaths). SMRs were also raised for laryngeal cancer (240; 95 to 505; 5 deaths), liver cancer (241; 126 to 420; 9 deaths), pancreatic cancer (224; 98 to 443; 6 deaths) and multiple myeloma (429; 117 to 1,109; 3 deaths). The authors concluded that the lung and pleural excesses can be causally related to asbestos exposure. They said a causal role in the laryngeal, pancreatic and multiple myeloma excesses could not be conclusively proven. They thought the liver excess probably reflected spread of lung cancer.

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 (historical) cohort mortality study comparing observed deaths with deaths expected from regional rates, supplemented by a review of available clinical and pathological records ('best evidence' approach)
• Who was studied: 734 male workers hired between 1 January 1945 and 31 December 1969 at a plant building and repairing railway carriages. Vital status was checked at 31 December 1997 and mortality was analysed for 1970-97, using Tuscany Region rates for comparison. 449 were alive and 243 had died; 44 deaths before 1970 were excluded, leaving 199 deaths in the analysis.
• Exposure: Asbestos insulation of railway carriages: chrysotile boards in specific parts (e.g. around heating) from the 1940s, and crocidolite-containing mixtures sprayed on the entire internal surface of carriages from the 1950s. Exposure came from the work itself and from contaminated air. Workers other than the insulators had no protective equipment. No fibre concentration measurements were available.
• Main results:
  • In the whole cohort, overall mortality was not above the expected value: 199 deaths observed versus 199.37 expected, SMR 100, 90% CI 89-112.
  • Pleural cancer in the cohort: SMR 1,327, 90% CI 523-2,790, 5 observed deaths (0.38 expected).
  • Four of the five pleural cancer deaths were confirmed mesotheliomas, three with histological diagnoses and one from clinical records only. Two further mesothelioma cases, a welder and an electrician, were alive at the end of the study.
  • Lung cancer in the cohort: SMR 124, 90% CI 87-172, 26 observed deaths (20.99 expected).
  • Laryngeal cancer in the cohort: SMR 240, 90% CI 95-505, 5 observed deaths.
  • Liver cancer: SMR 241, 90% CI 126-420, 9 observed deaths. Pancreatic cancer: SMR 224, 90% CI 98-443, 6 observed deaths.
  • Multiple myeloma in the cohort: SMR 429, 90% CI 117-1,109, 3 observed deaths.
  • The authors suggested the liver cancer excess could be disregarded as probably reflecting lung cancer that had spread to the liver.
  • The excess of respiratory tract cancers was evenly distributed between workers 21-30 years and over 31 years since first exposure.
• The authors' conclusion: The authors concluded that the excess of lung and pleural cancers can be causally related to asbestos exposure in railway carriage manufacture. They stated that a causal role of asbestos in the raised SMRs for laryngeal and pancreatic cancers and multiple myeloma cannot be conclusively proven.
• Limitations the authors state:
  • No measurements of asbestos fibre concentrations were available.
  • 42 subjects (6%) were lost to follow-up, and 8 causes of death (4%) could not be ascertained.
  • Misclassification on death certificates may have led to some underestimation of lung and pleural cancer deaths.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, confidence interval, Pleura, Myeloma, Neoplasm.

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