Cumulative asbestos exposure and mortality from asbestos related diseases in a pooled analysis of 21 asbestos cement cohorts in Italy

Our plain-English summary of Cumulative asbestos exposure and mortality from asbestos related diseases in a pooled analysis of 21 asbestos cement cohorts in Italy, by F. Luberto, D. Ferrante, S. Silvestri, et al (Environmental Health, 2019).

The study

• Authors: F. Luberto, D. Ferrante, S. Silvestri, A. Angelini, F. Cuccaro, A.M. Nannavecchia, E. Oddone, M. Vicentini, F. Barone-Adesi, T. Cena, D. Mirabelli, L. Mangone, F. Roncaglia, O. Sala, S. Menegozzo, R. Pirastu, D. Azzolina, S. Tunesi, E. Chellini, L. Miligi, P. Perticaroli, A. Pettinari, V. Bressan, E. Merler, P. Girardi, L. Bisceglia, A. Marinaccio, S. Massari, C. Magnani, working group
• Journal: Environmental Health
• Published: 2019;18(1):71
• Cited by: 44 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Despite the available information on cancer risk, asbestos is used in large areas in the world, mostly in the production of asbestos cement. Moreover, questions are raised regarding the shape of the dose response relation, the relation with time since exposure and the association with neoplasms in various organs. We conducted a study on the relationship between cumulative asbestos exposure and mortality from asbestos related diseases in a large Italian pool of 21 cohorts of asbestos-cement workers with protracted exposure to both chrysotile and amphibole asbestos.

Methods: The cohort included 13,076 workers, 81.9% men and 18.1% women, working in 21 Italian asbestos-cement factories, with over 40 years of observation. Exposure was estimated by plant and period, and weighted for the type of asbestos used. Data were analysed with consideration of cause of death, cumulative exposure and time since first exposure (TSFE), and by gender. SMRs were computed using reference rates by region, gender and calendar time. Poisson regression models including cubic splines were used to analyse the effect of cumulative exposure to asbestos and TSFE on mortality for asbestos-related diseases. 95% Confidence Intervals (CI) were computed according to the Poisson distribution.

Results: Mortality was significantly increased for 'All Causes' and 'All Malignant Neoplasm (MN)', in both genders. Considering asbestos related diseases (ARDs), statistically significant excesses were observed for MN of peritoneum (SMR: men 14.19; women 15.14), pleura (SMR: 22.35 and 48.10), lung (SMR: 1.67 and 1.67), ovary (in the highest exposure class SMR 2.45), and asbestosis (SMR: 507 and 1023). Mortality for ARDs, in particular pleural and peritoneal malignancies, lung cancer, ovarian cancer and asbestosis increased monotonically with cumulative exposure. Pleural MN mortality increased progressively in the first 40 years of TSFE, then reached a plateau, while peritoneal MN showed a continuous increase. The trend of lung cancer SMRs also showed a flattening after 40 years of TSFE. Attributable proportions for pleural, peritoneal, and lung MN were respectively 96, 93 and 40%.

Conclusions: Mortality for ARDs was associated with cumulative exposure to asbestos. Risk of death from pleural MN did not increase indefinitely with TSFE but eventually reached a plateau, consistently with reports from other recent studies.

In plain English

This study pooled 21 cohorts of Italian asbestos cement workers. It followed 12,578 workers (10,275 men, 2,303 women) for over 40 years, counting deaths from 1970. Exposure, mostly to chrysotile with some crocidolite and amosite, was estimated by plant and year and weighted by fiber type. Compared with regional rates, pleural cancer deaths were 22.35 times expected in men (95% confidence interval 19.91 to 25.00) and 48.10 times in women (38.63 to 59.19). Figures for men and women were 14.19 (11.57 to 17.23) and 15.14 (10.29 to 21.50) for peritoneal cancer, 1.67 (1.56 to 1.79) and 1.67 (1.18 to 2.29) for lung cancer, and 507.22 (455.32 to 563.41) and 1023.34 (761.95 to 1345.52) for asbestosis. The authors attributed women's higher figures to lower female death rates generally. Ovarian cancer mortality was not significantly raised overall but was in some subgroups, including women with the highest cumulative exposure. Pleural cancer mortality leveled off about 40 years after first exposure, while peritoneal cancer mortality kept rising. The authors concluded these deaths were associated with cumulative exposure.

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: Pooled analysis of 21 asbestos cement worker mortality cohorts. Deaths were compared with regional reference rates (SMRs), and Poisson regression, including cubic splines, was used for cumulative exposure and time since first exposure.
• Who was studied: 12,578 workers (10,275 men, 2,303 women) from 21 Italian asbestos cement factories, all hired before 1993. Follow-up ran to December 31, 2010 (three Tuscany cohorts and one Lazio cohort) or to December 31, 2012 or later (the other 17). Analyses were restricted to deaths and person-years from January 1, 1970.
• Exposure: Asbestos cement manufacture by the Hatschek process. The factories used mostly chrysotile (from Italy, Canada and the former Soviet Union), plus amphiboles (mostly crocidolite, a small percentage of amosite). Reported levels were 0.2 to 45 fibres/cc before 1980, 0.2 to 11 in 1980 to 1989, and below 0.1 to 0.3 after 1989. Cumulative exposure was estimated by plant and year and weighted by fiber type using potency factors of 1:14:71 for chrysotile, amosite and crocidolite. The tertile cut points were 54.0 and 620.0 f/ml-years.
• Main results:
  • Pleural cancer deaths: 305 in men (SMR 22.35, 95% CI 19.91 to 25.00) and 89 in women (SMR 48.10, 95% CI 38.63 to 59.19). Peritoneal cancer deaths: 102 in men (SMR 14.19, 95% CI 11.57 to 17.23) and 31 in women (SMR 15.14, 95% CI 10.29 to 21.50). Lung cancer deaths: 820 in men (SMR 1.67, 95% CI 1.56 to 1.79) and 38 in women (SMR 1.67, 95% CI 1.18 to 2.29). All were statistically significant.
  • Asbestosis deaths: 348 in men (SMR 507.22, 95% CI 455.32 to 563.41) and 51 in women (SMR 1023.34, 95% CI 761.95 to 1345.52).
  • The authors stated that the higher SMRs in women for pleural and peritoneal cancer reflect lower female reference death rates, not a higher risk or greater sensitivity to asbestos.
  • Ovarian cancer: 19 deaths overall (SMR 1.50, 95% CI 0.90 to 2.34), not statistically significant. In the highest tertile of cumulative exposure there were 13 deaths (SMR 2.40, 95% CI 1.28 to 4.10). The authors also reported significant increases in women who started employment before 1950, were employed more than 30 years, or were more than 50 years past first exposure.
  • Mortality from pleural and peritoneal cancer, lung cancer, ovarian cancer and asbestosis increased with cumulative exposure. For men, pleural cancer SMRs by tertile were 11.27, 20.77 and 29.97. The lung cancer trend was statistically significant in men but irregular in women.
  • Pleural cancer mortality rose over roughly the first 40 years after first exposure and then plateaued, while peritoneal cancer mortality showed a continuous increase. Lung cancer mortality also flattened after 40 years.
  • Attributable proportions were 96% for pleural cancer, 93% for peritoneal cancer and 40% for lung cancer.
  • Mortality from cancers of the larynx, pharynx, stomach, colon and rectum was not significantly higher than expected; for men, the larynx SMR was 1.20 (95% CI 0.89 to 1.58).
  • In men, deaths from cardiovascular diseases (SMR 0.87, 95% CI 0.83 to 0.92) and neurological diseases were significantly lower than expected. The authors interpreted this as a healthy worker effect.
• The authors' conclusion: The authors concluded that mortality from asbestos-related diseases was associated with cumulative asbestos exposure. They also concluded that the risk of death from pleural cancer did not increase indefinitely with time since first exposure but eventually reached a plateau, while peritoneal cancer mortality kept increasing.
• Limitations the authors state:
  • Individual tasks and jobs were unknown, so exposure was based on plant-and-period averages applied to all workers in a cohort.
  • Reliance on death certificates could have misclassified mesothelioma as other cancers, such as metastases or lung cancer, in either direction.
  • Asbestosis deaths were counted from the underlying cause of death only, so SMRs may be underestimated.
  • Mortality data are not very sensitive for cancers with long survival, such as laryngeal cancer.
  • There was no individual smoking information, and the combined effect of smoking and asbestos could not be assessed.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis.

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Meta-Analysis, Asbestos-Cement, Neoplasm, Chrysotile, Amphibole Asbestos, Cumulative Exposure, confidence interval.

Related studies

• Mortality for Mesothelioma and Lung Cancer in a Cohort of Asbestos Cement Workers in BARI (Italy): Time Related Aspects of Exposure — F. Cuccaro, A.M. Nannavecchia, et al. (2019)
• Mortality in asbestos cement workers in Pavia, Italy: A cohort study — E. Oddone, D. Ferrante, et al. (2017)
• A cohort study on mortality among wives of workers in the asbestos cement industry in Casale Monferrato, Italy — C. Magnani, B. Terracini, et al. (1993)
• Mortality in a cohort of cement workers in a plant of Central Italy — F. Giordano, V. Dell'orco, et al. (2012)
• Cholangiocarcinoma and Occupational Exposure to Asbestos: Insights From the Italian Pooled Cohort Study — S. Curti, M. Gallo, et al. (2024)
• Cancer risk after cessation of asbestos exposure: a cohort study of Italian asbestos cement workers — C. Magnani, D. Ferrante, et al. (2008)

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