Mortality from cancer and other causes among Italian chrysotile asbestos miners

Our plain-English summary of Mortality from cancer and other causes among Italian chrysotile asbestos miners, by E. Pira, C. Romano, F. Donato, et al (Occupational and Environmental Medicine, 2017).

The study

• Authors: E. Pira, C. Romano, F. Donato, C. Pelucchi, C. Vecchia, P. Boffetta
• Journal: Occupational and Environmental Medicine
• Published: 2017;74(8):558-563
• Cited by: 28 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objective: To investigate the long-term mortality of a cohort of Italian asbestos miners.

Methods: The cohort included 1056 men employed in a chrysotile mine between 1930 and 1990, who were followed up during 1946-2014, for a total of 37 471 person-years of observation. Expected deaths and SMRs were computed using national and local (after 1980, when available) reference.

Results: A total of 294 (27.8%) subjects were alive and at the end of follow-up, 722 (68.4%) were dead and 40 (3.8%) were lost to follow-up. The SMR for overall mortality was 1.35 (95%CI 1.25 to 1.45). The SMR for pleural cancer, based on seven observed deaths, was 5.54 (95% CI 2.22 to 11.4) and related to time since first exposure, but not to duration of employment, cumulative exposure or time since last exposure. The SMR for lung cancer was 1.16 (95% CI 0.87 to 1.52; 53 observed deaths), with no excess among workers with cumulative exposure below 100 fibre/mL-years (SMR 0.82; 95% CI 0.44 to 1.40).

Conclusions: The update of the follow-up of this cohort confirmed an increased mortality from pleural cancer mortality in miners exposed to chrysotile and a lack of significant increase in lung cancer mortality.

© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

In plain English

This study updated the death records of men who had worked at the Balangero chrysotile asbestos mine in northwestern Italy. The authors followed 1056 men employed there for at least one year between 1930 and 1989, tracked deaths from 1946 to 2014, and compared them with deaths expected from Italian national rates (Piedmont regional rates from 1981). By the end, 722 men (68.4%) had died. Overall deaths were higher than expected (SMR 1.35, 95% CI 1.25 to 1.45). Pleural cancer deaths were raised (seven deaths; SMR 5.54, 95% CI 2.22 to 11.4). All of these deaths occurred 30 or more years after first exposure, and no trend was found with duration of employment. Lung cancer deaths were not significantly raised (53 deaths; SMR 1.16, 95% CI 0.87 to 1.52). There was one peritoneal cancer death. Deaths from liver cirrhosis and from accidents and violence were raised. The authors concluded that the update confirmed increased pleural cancer mortality and no significant increase in lung cancer mortality. They noted small numbers, limited smoking data, estimated early exposure levels and reliance on death certificates.

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: Cohort mortality study (an update of earlier follow-ups of the same workforce) comparing observed deaths with expected deaths (SMRs), using national male death rates before 1981 and Piedmont regional rates from 1981 onwards
• Who was studied: 1056 men employed for at least 1 year between 1930 and 1989 at the Balangero mine in Northwestern Italy (contract workers excluded), followed for deaths from 1946 to 2014, for a total of 37 471 person-years
• Exposure: Chrysotile asbestos mining and milling. Jobs were grouped as mining, crushing, waste dumping, screening and fibre separation, bagging and storage, and maintenance. Cumulative exposure was estimated in fibre/mL-years, with exposure levels before 1969 reconstructed by simulation.
• Main results:
  • At the end of follow-up, 294 of the 1056 men (27.8%) were alive, 722 (68.4%) had died and 40 (3.8%) had emigrated or were lost to follow-up.
  • Overall mortality in the cohort was higher than expected: 722 observed versus 533.4 expected deaths (SMR 1.35, 95% CI 1.25 to 1.45).
  • Mortality from all cancers combined was close to expectation: 176 observed versus 165.3 expected deaths (SMR 1.07, 95% CI 0.91 to 1.23).
  • Pleural cancer mortality in the cohort was raised: SMR 5.54 (95% CI 2.22 to 11.4), based on seven observed deaths.
  • All seven pleural cancer deaths occurred 30 or more years after first exposure, five of them 40 or more years after first exposure.
  • No trend in pleural cancer SMRs was found by duration of employment, cumulative exposure or any other exposure measure considered.
  • Pleural cancer mortality remained elevated 30 or more years after exposure stopped.
  • Among workers with cumulative exposure below 100 fibre/mL-years, the SMR for pleural cancer was 5.84 (95% CI 1.20 to 17.1).
  • Lung cancer mortality in the whole cohort was not significantly raised: SMR 1.16 (95% CI 0.87 to 1.52), 53 observed versus 45.5 expected deaths.
  • Among workers with cumulative exposure below 100 fibre/mL-years, the SMR for lung cancer was 0.82 (95% CI 0.44 to 1.40).
  • Among workers with cumulative exposure below 25 fibre/mL-years, the lung cancer SMR was 2.40 (95% CI 0.49 to 7.01), based on three deaths.
  • An internal (Poisson regression) analysis of lung cancer found no significant trend for any of the exposure variables considered.
  • Only one peritoneal cancer death occurred: SMR 1.09 (95% CI 0.03 to 6.08).
  • SMRs for upper aerodigestive tract cancers were increased but not statistically significant: oral cavity and pharynx 1.35 (95% CI 0.54 to 2.77), oesophagus 1.23 (95% CI 0.40 to 2.87), larynx 1.58 (95% CI 0.68 to 3.11).
  • Liver cirrhosis caused 62 deaths against 21.2 expected (SMR 2.92, 95% CI 2.24 to 3.74).
  • Accidents and violence caused 58 deaths against 33.1 expected (SMR 1.75, 95% CI 1.33 to 2.26).
  • The authors listed asbestosis (24 deaths) and tuberculosis (16 deaths) among other causes of death with increased mortality. No SMRs were given for these causes.
• The authors' conclusion: The authors concluded that the extended follow-up of this cohort of asbestos (primarily chrysotile) miners confirmed an increased mortality from pleural cancer and a lack of significantly increased mortality from lung cancer.
• Limitations the authors state:
  • Smoking data were available for only 14.5% of cohort members, and the authors noted possible confounding by smoking, alcohol and job exposures outside the mine.
  • Occupational exposure to asbestos in other jobs might have contributed to the excess pleural cancer mortality.
  • Fibre measurements were available only from 1969, so exposure levels for earlier years were simulated. The authors said these values have considerable limitations.
  • Relying on death certificates could give low sensitivity and specificity for diagnosing mesothelioma, possibly biasing the SMR in either direction.
  • The small numbers of pleural and peritoneal cancer deaths limited statistical power.
  • Statistical power for lung cancer among workers with less than 25 fibre/mL-years was low.
  • The authors said other explanations for the lung cancer finding could not be excluded, such as exclusion of highly exposed contract workers, competing deaths from other lung diseases and asbestosis, and differences in smoking habits.

Topics

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

Medical terms in this study, explained in our Lexicon: Chrysotile, Cumulative Exposure, Lung Cancer.

Related studies

• Mortality from cancer and other causes in the Balangero cohort of chrysotile asbestos miners — E. Pira, C. Pelucchi, et al. (2009)
• The 1891-1920 birth cohort of Quebec chrysotile miners and millers: development from 1904 and mortality to 1992 — F.D. Liddell, A.D. McDonald, et al. (1997)
• An update of cancer mortality among chrysotile asbestos miners in Balangero, northern Italy — G. Piolatto, E. Negri, et al. (1990)
• Mortality of Talc Miners and Millers From Val Chisone, Northern Italy: An Updated Cohort Study — E. Pira, M. Coggiola, et al. (2017)
• Mortality in a Chinese chrysotile miner cohort — X. Wang, S. Lin, et al. (2012)
• The 1891-1920 birth cohort of Quebec chrysotile miners and millers: mortality 1976-88 — J.C. McDonald, F.D. Liddell, et al. (1993)

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