Mortality in asbestos cement workers in Pavia, Italy: A cohort study

Our plain-English summary of Mortality in asbestos cement workers in Pavia, Italy: A cohort study, by E. Oddone, D. Ferrante, S. Tunesi, et al (American Journal of Industrial Medicine, 2017).

The study

• Authors: E. Oddone, D. Ferrante, S. Tunesi, C. Magnani
• Journal: American Journal of Industrial Medicine
• Published: 2017;60(10):852-866
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: The aim of this study was to describe the mortality of a cohort of asbestos-cement workers in the largest plant in the most industrialized Italian region (Lombardy).

Methods: A cohort study was carried out on 1818 subjects, corresponding to 47 536.1 person-years of observation. Standardized mortality ratios (SMRs) were computed for the major causes of death.

Results: Increased SMRs were observed for pleural, peritoneal and lung cancers, and for asbestosis (SMR 26.73, 95% Confidence Interval (CI) 20.99-33.55; 9.15, 95%CI 5.00-15.34; 1.48, 95%CI 1.27-1.72; and 368.05, 95%CI 214.40-589.29, respectively). No excess in mortality for laryngeal cancer was observed (SMR 0.70, 95%CI 0.30-1.39). An increased mortality for ovarian cancer (SMR 3.64, 95%CI 0.99-9.33) was observed, although it was not statistically significant. Among men, mortality for pleural malignant mesothelioma was observed to be related to the duration of exposure, though not to latency.

Conclusions: The results of this study are generally consistent with present knowledge. Conversely, our results do not support the hypothesis that pleural malignant mesothelioma risk indefinitely increases after exposure, suggesting instead that the alternative hypothesis of a risk plateau or decrease after a time since first exposure of more than 40 years is more consistent with the observed data.

© 2017 Wiley Periodicals, Inc.

In plain English

This cohort study followed 1818 workers (1663 men, 155 women) at the Fibronit asbestos-cement plant in Broni, Italy, employed on 1 January 1950 or hired by 1992; 277 started before 1940 and 257 in 1940-1949. The blend contained chrysotile, crocidolite and, as an additive, amosite. Deaths in 1970-2014 were compared with Lombardy rates. Of 1338 deaths, 74 were from pleural cancer (standardized mortality ratio, SMR, 26.73; 95% confidence interval, CI, 20.99 to 33.55). Deaths were also raised for peritoneal cancer (SMR 9.15, CI 5.00 to 15.34), lung cancer (SMR 1.48, CI 1.27 to 1.72) and asbestosis (17 deaths, all men). Laryngeal cancer deaths were not raised (SMR 0.70, CI 0.30 to 1.39); the ovarian cancer excess (four deaths; SMR 3.64, CI 0.99 to 9.33) was not statistically significant. Pleural cancer deaths rose with duration of exposure but, among men, showed no statistically significant trend with time since first exposure. The authors concluded that a plateau or decrease in pleural mesothelioma risk beyond 40 years since first exposure fit their data better than an indefinite rise. Data on jobs and individual exposure were lacking.

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 comparing observed deaths with deaths expected from regional rates (standardized mortality ratios)
• Who was studied: 1818 workers (1663 men, 155 women) of the Fibronit asbestos-cement plant in Broni (Pavia, Lombardy, Italy). They were already employed on 1 January 1950 or hired afterwards, up to 1992. In Table 1, 277 were first exposed before 1940 and 257 in 1940-1949. Follow-up ran from 1 January 1970 to 31 December 2014, giving 47 536.1 person-years. 1338 had died by the end of follow-up, 20 were lost to follow-up, and the cause of death was traced for 85.4% of those who died.
• Exposure: Work in an asbestos-cement factory making tubes, sheets, chimneys, pipes and other products. The blend was Portland cement with chrysotile and crocidolite, with amosite used only as an additive. Asbestos made up 10-15% of sheets and 30% of tubes by dry weight. Crocidolite was used until the mid-1980s, amosite until 1990 and chrysotile until 1993. No fiber monitoring data exist before 1981. Exposure was measured only as duration of employment and time since first employment.
• Main results:
  • Whole cohort: deaths were higher than expected for pleural cancer (SMR 26.73, 95% CI 20.99-33.55; 74 deaths), peritoneal cancer (SMR 9.15, 95% CI 5.00-15.34), lung cancer (SMR 1.48, 95% CI 1.27-1.72) and asbestosis (SMR 368.05, 95% CI 214.40-589.29).
  • All 17 asbestosis deaths were in men.
  • Whole cohort: deaths from laryngeal cancer were not higher than expected (SMR 0.70, 95% CI 0.30-1.39).
  • Women: four deaths from ovarian cancer (SMR 3.64, 95% CI 0.99-9.33). This increase was not statistically significant.
  • Overall mortality and mortality from all malignancies were significantly increased in both men and women.
  • Pleural cancer and peritoneal cancer deaths increased with duration of exposure. Lung cancer and asbestosis deaths seemed unrelated to duration.
  • Lung cancer and peritoneal cancer deaths increased with time since first exposure.
  • Among men, pleural cancer deaths showed no statistically significant trend with time since first exposure (P = 0.187). Among women there was an inverse trend (P = 0.011), based on only eight cases.
  • Deaths from cardiovascular diseases, and ischemic heart diseases in particular, were significantly lower than expected. Deaths from cirrhosis were significantly higher than expected.
• The authors' conclusion: The authors concluded that their results were generally consistent with existing knowledge. In their view, the results did not support the idea that pleural malignant mesothelioma risk keeps increasing indefinitely after exposure. They found a plateau or decrease after more than 40 years since first exposure more consistent with the data. They suggested this may point to clearance of asbestos from the lung, which they said deserves further study.
• Limitations the authors state:
  • There was no information on job titles or tasks, so individual exposure and cumulative dose could not be assessed. Duration of employment was the only proxy for exposure, and the authors called it a very weak indicator of exposure severity.
  • The small number of deaths among women prevented conclusions from time-related analyses in women.
  • Ovarian cancer deaths could have been misclassified peritoneal mesotheliomas. No pathology review was possible because only death certificates were available.
  • The trend results for pleural mesothelioma by time since first exposure were affected by few cases in the 20-29 year class.
  • Analyses were limited to deaths and person-years from 1970 onward, because regional reference rates were only available from then.

Topics

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

Medical terms in this study, explained in our Lexicon: Asbestos-Cement, Cohort Study, standardized mortality ratio (SMR), Lung Cancer, confidence interval, Laryngeal Cancer, Ovarian Cancer, Malignant Mesothelioma.

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)
• Cumulative asbestos exposure and mortality from asbestos related diseases in a pooled analysis of 21 asbestos cement cohorts in Italy — F. Luberto, D. Ferrante, et al. (2019)
• Mortality in a cohort of cement workers in a plant of Central Italy — F. Giordano, V. Dell'orco, et al. (2012)
• 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)
• Cancer mortality and incidence of mesothelioma in a cohort of wives of asbestos workers in Casale Monferrato, Italy — D. Ferrante, M. Bertolotti, et al. (2007)
• 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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