Updated mortality study of a cohort of asbestos textile workers

Our plain-English summary of Updated mortality study of a cohort of asbestos textile workers, by E. Pira, C. Romano, F.S. Violante, et al (Cancer Medicine, 2016).

The study

• Authors: E. Pira, C. Romano, F.S. Violante, A. Farioli, G. Spatari, C. La Vecchia, P. Boffetta
• Journal: Cancer Medicine
• Published: 2016;5(9):2623-8
• Cited by: 29 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Limited information is available on risk of peritoneal mesothelioma after asbestos exposure, and in general on the risk of cancer after cessation of asbestos exposure. We updated to 2013 the follow-up of a cohort of 1083 female and 894 male textile workers with heavy asbestos exposure (up to 100 fb/mL), often for short periods. A total of 1019 deaths were observed, corresponding to a standardized mortality ratio (SMR) of 1.68 (95% confidence interval [CI]: 1.57-1.78). SMRs were 29.1 (95% CI: 21.5-38.6) for peritoneal cancer, 2.96 (95% CI: 2.50-3.49) for lung cancer, 33.7 (95% CI: 25.7-43.4) for pleural cancer, and 3.03 (95% CI: 1.69-4.99) for ovarian cancer. For pleural and peritoneal cancer, there was no consistent pattern of risk in relation to time since last exposure, whereas for lung cancer there was an indication of a decline in risk after 25 years since last exposure. The findings of this unique cohort provide novel data for peritoneal cancer, indicating that - as for pleural cancer - the excess risk does not decline up to several decades after cessation of exposure.

© 2016 The Authors. Cancer Medicine published by John Wiley & Sons Ltd.

In plain English

This study updated death records, to November 2013, for 1083 women and 894 men who worked at an asbestos textile factory in Northern Italy between 1946 and 1984. The factory mainly used chrysotile, but crocidolite was also present. Average exposure levels as high as 100 fb/mL were measured in the late 1960s. 1019 workers had died; the standardized mortality ratio (SMR) for all causes was 1.68 (95% CI 1.57–1.78). SMRs were 29.1 (95% CI 21.5–38.6) for peritoneal cancer (48 deaths), 33.7 (25.7–43.4) for pleural cancer (60 deaths), 2.96 (2.50–3.49) for lung cancer (143 deaths) and 3.03 (1.69–4.99) for ovarian cancer (15 deaths). Time since last exposure was approximated by time since last factory employment. On that measure pleural and peritoneal cancer showed no consistent pattern and no sign of a decrease, while for lung cancer the SMR declined after 25 years. The authors concluded that, as for pleural cancer, the excess peritoneal cancer risk does not decline up to several decades after exposure stops. They noted they lacked individual exposure data and smoking information, and relied 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 (updated follow-up of a previously reported cohort), comparing observed deaths with expected deaths (standardized mortality ratios) and using Poisson regression for time-related exposure variables
• Who was studied: 1083 women and 894 men who worked at an asbestos textile factory in Northern Italy between 1946 and 1984. They were followed to November 30, 2013, and censored at age 85. The analysis covered 74,126 person-years.
• Exposure: Work in an asbestos textile factory. The main fiber was chrysotile, and crocidolite was also present in unknown proportions over time. Average levels as high as 100 fb/mL were measured in the opening and carding departments in the late 1960s, 5–25 fb/mL in the early 1970s, and 2 fb/mL or less in the late 1970s. Exposure was often for short periods.
• Main results:
  • 1019 of the 1977 workers had died. The SMR for all causes, both sexes combined, was 1.68 (95% CI: 1.57–1.78).
  • Peritoneal cancer, both sexes: 48 deaths, SMR 29.1 (95% CI: 21.5–38.6). Women: 36 deaths, SMR 41.8 (29.3–57.9). Men: 12 deaths, SMR 15.3 (7.88–27.0).
  • Pleural cancer, both sexes: 60 deaths, SMR 33.7 (95% CI: 25.7–43.4). Women: 36 deaths, SMR 60.8 (42.6–84.2). Men: 24 deaths, SMR 20.2 (13.0–30.1).
  • Lung cancer, both sexes: 143 deaths, SMR 2.96 (95% CI: 2.50–3.49). Women: SMR 5.29. Men: SMR 2.51.
  • Ovarian cancer (women): 15 deaths, SMR 3.03 (95% CI: 1.69–4.99).
  • Time since last exposure was approximated by time since last employment. On that measure, there was no consistent pattern of SMRs, and no evidence of a decrease, for pleural and peritoneal cancer.
  • Using time since last employment, the lung cancer SMR was 2.08 (95% CI: 1.36–3.05) at 35 or more years. In the categories from 3 to 34 years it ranged from 3.29 to 3.67.
  • In regression models adjusted for sex and age, duration of employment had the strongest association with lung cancer. For 10 or more years of employment versus less than 1 year, the mortality rate ratio was 2.95 (1.88–4.62), with a trend p-value less than 0.001. For pleural cancer there was no association with duration of employment (trend p-value 0.4).
  • Pleural cancer was associated with time since last employment. Compared with less than 15 years, the mortality rate ratio was 3.56 (1.53–8.31) at 15–29 years and 3.10 (1.26–7.67) at 30 or more years.
  • Among workers employed for less than 1 year, there were 10 deaths from peritoneal cancer, 31 from lung cancer and 16 from pleural cancer.
  • Excluding the 120 workers with asbestos exposure before being hired did not materially change the results. The SMRs were then 29.5 for peritoneal cancer (46 deaths), 2.97 for lung cancer (134 deaths) and 32.3 for pleural cancer (54 deaths).
  • Esophageal cancer was increased in women (4 deaths, SMR 6.45, 1.76–16.5) but not in men. The authors said this inconsistency between the sexes detracts from a causal interpretation.
• The authors' conclusion: The authors concluded that the cohort provides new evidence for peritoneal cancer: as for pleural cancer, the excess risk does not decline up to several decades after exposure stops. They also said the peritoneal mesothelioma results are more difficult to interpret until death-certificate diagnoses are validated.
• Limitations the authors state:
  • No individual exposure data.
  • Reliance on death certificates for cause of death, which can be particularly problematic for pleural and peritoneal cancer.
  • No information on confounders such as tobacco smoking for lung cancer, or alcohol drinking for oral and pharyngeal cancer.
  • Incomplete information on work in other industries with asbestos exposure. This may misclassify time-related variables such as time since last exposure.
  • Mortality data refer to pleural and peritoneal cancer, so mesothelioma diagnoses may be misclassified. In women, peritoneal cancer may also be misclassified as ovarian cancer.
  • Regional reference rates may have underestimated asbestos-related risk, because much of the reference population was also exposed to asbestos.
  • The decline in lung cancer risk may partly reflect competing deaths from mesothelioma.

Topics

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

Medical terms in this study, explained in our Lexicon: Peritoneal Mesothelioma, Asbestos Exposure, standardized mortality ratio (SMR), confidence interval, Lung Cancer, Ovarian Cancer.

Related studies

• Mortality of Talc Miners and Millers From Val Chisone, Northern Italy: An Updated Cohort Study — E. Pira, M. Coggiola, et al. (2017)
• Cancer mortality in a cohort of asbestos textile workers — E. Pira, C. Pelucchi, et al. (2005)
• Temporal Patterns of Exposure to Asbestos and Risk of Asbestosis: An Analysis of a Cohort of Asbestos Textile Workers — A. Farioli, F.S. Violante, et al. (2018)
• Validation of the diagnosis of mesothelioma and BAP1 protein expression in a cohort of asbestos textile workers from Northern Italy — P. Boffetta, L. Righi, et al. (2018)
• Relationship of mortality to measures of environmental asbestos pollution in an asbestos textile factory — J. Peto, R. Doll, et al. (1985)
• Occupational cancer of the urinary bladder in dyestuffs operatives and of the lung in asbestos textile workers and iron-ore miners — G.M. Bonser, J.S. Faulds, et al. (1955)

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