Mortality and mesothelioma incidence among chrysotile asbestos miners in Balangero, Italy: A cohort study

Our plain-English summary of Mortality and mesothelioma incidence among chrysotile asbestos miners in Balangero, Italy: A cohort study, by D. Ferrante, D. Mirabelli, S. Silvestri, et al (American Journal of Industrial Medicine, 2020).

The study

• Authors: D. Ferrante, D. Mirabelli, S. Silvestri, D. Azzolina, A. Giovannini, P. Tribaudino, C. Magnani
• Journal: American Journal of Industrial Medicine
• Published: 2020;63(2):135-145
• Cited by: 29 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: We studied cancer mortality and mesothelioma incidence in 974 male workers employed at least 6 months at the Balangero mine (Italy), the largest chrysotile mine in Western Europe, active from 1917 to 1985.

Methods: Vital status as of 31 May 2013, causes of deaths and mesothelioma incidence from 1990 were ascertained. Past exposure to asbestos by working area and calendar period was estimated, based on historical data of fibers concentrations. Individual cumulative exposure was assessed by applying estimates to the job history of cohort members. Standardized mortality ratios (SMRs) for selected causes and standardized incidence ratios for malignant mesothelioma (MM) were calculated based on regional reference rates. Poisson regression analysis was used to study MM and lung cancer risk by latency, duration, and cumulative exposure.

Results: Mortality was increased for all causes (SMR = 1.28; 95% confidence interval [CI] = 1.17-1.40), pleural cancer (SMR = 4.30; 95% CI = 1.58-9.37), asbestosis (SMR = 375.06; 95% CI = 262.68-519.23). An increase was also found for lung cancer (SMR = 1.14; 95% CI = 0.81-1.55) and peritoneal cancer (SMR = 3.25; 95% CI = 0.39-11.75). The risk of both pleural and peritoneal cancer mortality and of mesothelioma incidence increased with increasing cumulative exposure, duration, and latency. Poisson regression analyses showed an increase in mesothelioma risk with cumulative asbestos exposure and suggest a similar trend for lung cancer. Asbestosis mortality also increased with cumulative exposure.

Conclusions: Among Balangero chrysotile miners and millers, the occurrence of malignant and nonmalignant asbestos-related diseases was increased by exposure, with dose-response relation. The study confirms the carcinogenicity of chrysotile asbestos, in particular for pleural mesothelioma.

© 2019 Wiley Periodicals, Inc.

In plain English

This cohort study followed 974 men employed at least 6 months at Italy's Balangero chrysotile asbestos mine. They were working there on 1 January 1946 or hired later, and follow-up ran to 31 May 2013. The Turin Public Prosecutor requested the study. The authors described the chrysotile as tremolite-free and estimated each worker's cumulative exposure. Compared with the Piedmont population, all-cause deaths were higher (SMR 1.28; 95% CI 1.17 to 1.40). So were deaths from pleural cancer (6 vs 1.4 expected; SMR 4.30, 95% CI 1.58 to 9.37) and from asbestosis (36 vs 0.1 expected). Lung cancer (40 vs 35.1) and peritoneal cancer (2 vs 0.6) deaths were raised, but not statistically significantly. Six pleural mesothelioma cases diagnosed 1990 to 2012 gave a standardized incidence ratio of 6.3 (95% CI 2.3 to 13.7). A regression combined these six cases with four pleural or peritoneal cancer deaths before 1990. Risk rose across cumulative exposure groups, with wide confidence intervals and a borderline trend. The authors concluded that asbestos-related diseases rose with exposure, with a dose-response relation, confirming chrysotile's carcinogenicity, particularly for pleural mesothelioma. They lacked smoking and alcohol 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: Cohort study (mortality and mesothelioma incidence) of mine workers, conducted at the request of the Public Prosecutor of the Turin Court
• Who was studied: 974 male workers employed for at least 6 months at the Balangero mine, Italy, who were active on 1 January 1946 or hired afterwards until the mine stopped. Vital status was followed to 31 May 2013. Mortality comparisons covered 1965 to 2013, and mesothelioma incidence covered 1990 to 2012.
• Exposure: Chrysotile asbestos from mining and milling. The ore was described as tremolite-free, with traces of balangeroite (a nonasbestos fibrous mineral). Individual cumulative exposure was estimated in fiber per milliliter × years, from area and year fiber concentration estimates applied to each worker's job history.
• Main results:
  • Overall mortality in the cohort was increased compared with the Piedmont population: SMR 1.28 (95% CI 1.17 to 1.40), or about 100 excess deaths over 389 expected.
  • Pleural cancer mortality was increased: 6 deaths observed vs 1.4 expected, SMR 4.30 (95% CI 1.58 to 9.37).
  • Asbestosis mortality was greatly increased: 36 deaths observed vs 0.1 expected, SMR 375.06 (95% CI 262.68 to 519.23).
  • Lung cancer deaths (40 observed vs 35.1 expected; SMR 1.14, 95% CI 0.81 to 1.55) and peritoneal cancer deaths (2 observed vs 0.6 expected; SMR 3.25, 95% CI 0.39 to 11.75) were increased but not statistically significant.
  • Six incident cases of pleural mesothelioma occurred from 1990 to 2012, giving a standardized incidence ratio of 6.3 (95% CI 2.3 to 13.7). No incident peritoneal mesothelioma cases were observed.
  • The Poisson regression of mesothelial malignancies included 10 subjects: six incident pleural mesothelioma cases diagnosed since 1990, plus four workers who died before 1990, two from pleural and two from peritoneal cancer.
  • In that regression, adjusted for latency, relative risk compared with under 27 f/mL-y was 5.6 (95% CI 0.5 to 57.6) for 27 to 345 f/mL-y. It was 12.6 (95% CI 0.9 to 171.0) for 346 or more f/mL-y. The trend test was borderline (p = 0.06). Per 100 f/mL-y, RR was 1.019 (95% CI 0.900 to 1.154).
  • For lung cancer, the latency-adjusted relative risk was 2.1 in the second and 2.2 in the third cumulative exposure tertile. The trend was not statistically significant.
  • Asbestosis mortality increased with cumulative exposure: RR 1.079 (95% CI 1.034 to 1.125) per 100 f/mL-y.
  • Deaths from cirrhosis and other chronic liver diseases were increased: 33 deaths, SMR 2.28.
• The authors' conclusion: The authors concluded that among Balangero chrysotile miners and millers, malignant and nonmalignant asbestos-related diseases increased with exposure, with a dose-response relation. They concluded that the study confirms the carcinogenicity of chrysotile asbestos, in particular for pleural mesothelioma.
• Limitations the authors state:
  • No information on smoking or alcohol use, which limits the lung and larynx cancer results and prevents analysis of asbestos-smoking interaction.
  • No information on other occupational or nonoccupational exposures.
  • Few mesothelioma cases, so confidence intervals were wide.
  • Exposure for past decades had to be reconstructed experimentally, because no measurements existed.
  • Collinearity limited the inclusion of several time-related variables in the regression models.
  • With only two deaths, no trend could be assessed for peritoneal cancer.

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelioma, Chrysotile, Cohort Study, Balangero Mine, Cumulative Exposure, standardized mortality ratio (SMR), Standardized Incidence Ratio (SIR), Malignant Mesothelioma.

Related studies

• Re Ferrante et al (2020). Mortality and mesothelioma incidence among chrysotile asbestos miners in Balangero, Italy: A cohort study — J. Schüz, H. Kromhout (2020)
• An update of cancer mortality among chrysotile asbestos miners in Balangero, northern Italy — G. Piolatto, E. Negri, et al. (1990)
• Mortality from cancer and other causes in the Balangero cohort of chrysotile asbestos miners — E. Pira, C. Pelucchi, et al. (2009)
• An update of cancer mortality among chrysotile asbestos miners in Balangero, northern Italy — R. Calisti, P. De Giuli, et al. (1992)
• 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)
• 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)

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