Mortality from Pleural and Lung Cancer in Railway Maintenance Workers

Our plain-English summary of Mortality from Pleural and Lung Cancer in Railway Maintenance Workers, by L. Scarso, M. Novelli, E.L. Negri, et al (Life, 2025).

The study

• Authors: L. Scarso, M. Novelli, E.L. Negri, C. Zunarelli, The Pleural Cancer Study Group, F.S. Violante
• Journal: Life
• Published: 2025;15(7)
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

(1) Background: Occupational exposure to asbestos remains a significant public health concern due to its association with pleural cancer and other cancers. This cohort study examines the incidence of asbestos-related diseases among railway carriage maintenance workers exposed to asbestos between 1960 and 1979 in Bologna, Italy. (2) Methods: A cohort of 2197 male workers was followed from 1960 onwards, with data collected on asbestos exposure, smoking habits, and mortality outcomes. The association of asbestos exposure and smoking with the risk of pleural cancer and lung cancer was assessed using Cox proportional hazards regression models. (3) Results: This study identified a substantial burden of asbestos-related pleural cancer, with an exponential increase in risk over time since the beginning of exposure. Our results suggest the lack of a multiplicative effect of asbestos exposure and smoking on lung cancer risk. The Cox models showed a significant association between smoking and lung cancer risk, with a hazard ratio of 3.26 (95% CI: 1.10-9.64, p = 0.03), less significant for asbestos exposure, with a hazard ratio of 1.42 (95% CI: 0.66-3.06). (4) Conclusions: This study provides valuable insights into the long-term health effects of occupational asbestos exposure and underscores the complex interaction between asbestos exposure and smoking in the development of lung cancer.

In plain English

This mortality cohort study followed 2,197 men employed for at least one day from 1960 to 1979 at a railway carriage maintenance company in Bologna, Italy. The asbestos was reported as mostly crocidolite, with some amosite. Workers were grouped as blue-collar (likely direct exposure) or white-collar (possibly indirect exposure), and vital status was checked on 31 December 2022. There were 103 pleural cancer deaths, a category combining older pleural cancer codes with later mesothelioma codes. The fitted pleural cancer incidence rate rose about 2.15 times per five-year interval since first exposure (95% CI 1.68 to 2.72). For blue-collar workers the pleural cancer hazard ratio was 1.86 (95% CI 0.76 to 4.58), which was not statistically significant. Of 109 lung cancer deaths, 22 had known smoking status. Current or former smokers had a hazard ratio of 3.26 (95% CI 1.10 to 9.64) compared with never-smokers. For blue-collar work the lung cancer hazard ratio was 1.42 (95% CI 0.66 to 3.06). Interaction analyses found no significant asbestos-smoking interaction, and the authors concluded that their data show a simple additive effect. They noted indirect exposure measures and incomplete smoking data.

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 mortality cohort study analysed with Cox proportional hazards regression
• Who was studied: 2,200 workers directly employed for at least one day between 1 January 1960 and 31 December 1979 at a railway carriage maintenance company in Bologna, Italy. The 3 women were excluded, leaving 2,197 men. Vital status was checked on 31 December 2022: 845 were alive, 1,303 had died and 49 had undetermined status.
• Exposure: Asbestos at the plant was reported as mostly crocidolite, with some amosite, based on 1980 measurements by phase contrast microscopy. No individual exposure measures were available, so workers were classed as blue-collar (likely direct exposure) or white-collar (possibly indirect exposure). Smoking status, recorded as smoker or past smoker versus never-smoker, came from 1990s health-check records.
• Main results:
  • There were 103 pleural cancer deaths: 98 of 1,065 (9.2%) in blue-collar workers and 5 of 114 (4.4%) in white-collar workers, a crude mortality ratio of 2.09. The first pleural cancer death was in 1979 and the first coded mesothelioma death in 1997.
  • Pleural cancer incidence was 0 in the first 10 years after first exposure and peaked at 0.40 per 1000 person-years in the 51 to 55 year interval. A power function fit showed the incidence rate increasing 2.15 times per interval (95% CI 1.68 to 2.72).
  • The mean time from start of exposure to pleural cancer was 39.5 years and the median was 40.9 years, with a range of 11.0 to 54.7 years.
  • Exposure duration was not clearly associated with pleural cancer: hazard ratio 0.97, p = 0.11.
  • For pleural cancer, blue-collar versus white-collar workers had a hazard ratio of 1.86 (95% CI 0.76 to 4.58, p = 0.18). The authors described this as an excess risk that was not statistically significant.
  • For lung cancer, the 22 deaths with smoking information gave current or former smokers a hazard ratio of 3.26 (95% CI 1.10 to 9.64, p = 0.03) compared with never-smokers. Across all 109 lung cancer deaths, blue-collar versus white-collar workers had a hazard ratio of 1.42 (95% CI 0.66 to 3.06, p = 0.37).
  • Lung cancer made up 18 of 154 deaths (11.7%) among smokers or ex-smokers and 4 of 91 deaths (4.4%) among never-smokers. It made up 102 of 1,068 deaths (9.6%) in blue-collar workers and 7 of 112 deaths (6.3%) in white-collar workers.
  • In a Monte Carlo simulation, the mean hazard ratio for the asbestos-by-smoking interaction was 1.7 and the median was 1.2 (p = 0.80; 95% CI 0.25 to 5.98). The mean RERI was 0.04 and the mean attributable proportion was 0.14, both with wide confidence intervals. The authors read these results as no significant interaction.
• The authors' conclusion: The authors concluded that their data show a simple additive effect of asbestos exposure and smoking on lung cancer risk. They also concluded that both should be considered in occupational health assessments.
• Limitations the authors state:
  • Exposure was measured only in 1980, so earlier exposure may have been higher. Job title is only an indirect estimate of exposure.
  • No information was available on workers at the plant who were employed by other employers.
  • Smoking data were missing for many workers and were filled in by multiple imputation. Only 671 workers (30.5%) provided smoking data.
  • Before 2009, some deaths coded as pleural cancer may have been pleural cancers other than mesothelioma, such as pleural metastases.
  • No standardization against an external population was done.
  • The study relied on death certificate codes, which are subject to bias, and on exposure status that was assigned retrospectively and may be imprecise.
  • Sample size was limited. The authors stated that more data or larger samples are needed for clearer conclusions on interaction.

Topics

Medical terms in this study, explained in our Lexicon: Lung Cancer, Occupational Exposure, Cohort Study, Asbestos Exposure, Habit, Hazard Ratio.

Related studies

• Mortality due to asbestos-related causes among railway carriage construction and repair workers — G. Battista, S. Belli, et al. (1999)
• Mortality among maintenance employees potentially exposed to asbestos in a refinery and petrochemical plant — S.P. Tsai, L.C. Waddell, et al. (1996)
• Asbestos exposure, smoking habits, and cancer incidence among production and maintenance workers in an electrochemical plant — B. Hilt, S. Langård, et al. (1985)
• Asbestos disease in maintenance workers of the chemical industry — R. Lilis, S. Daum, et al. (1979)
• Asbestos exposure and radiological abnormalities among maintenance and custodian workers in buildings with friable asbestos-containing materials — M. Matrat, J.C. Pairon, et al. (2004)
• Asbestos-related disease in custodial and building maintenance workers from a large municipal school district — J.R. Balmes, A. Daponte, et al. (1991)

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