Cancer risk after cessation of asbestos exposure: a cohort study of Italian asbestos cement workers

Our plain-English summary of Cancer risk after cessation of asbestos exposure: a cohort study of Italian asbestos cement workers, by C. Magnani, D. Ferrante, F. Barone-Adesi, et al (Occupational and Environmental Medicine, 2008).

The study

• Authors: C. Magnani, D. Ferrante, F. Barone-Adesi, M. Bertolotti, A. Todesco, D. Mirabelli, B. Terracini
• Journal: Occupational and Environmental Medicine
• Published: 2008;65(3):164-70
• Cited by: 95 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: We aimed to study mortality for asbestos related diseases and the incidence of mesothelioma in a cohort of Italian asbestos cement workers after cessation of asbestos exposure.

Methods: The Eternit factory operated from 1907 to 1986. The cohort included 3434 subjects active in 1950 or hired in 1950-86, ascertained from company records, without selections. Local reference rates were used for both mortality and mesothelioma incidence.

Results: Mortality was increased in both sexes for all causes (overall 1809 observed (obs) vs 1312.3 expected (exp); p<0.01), pleural (135 obs vs 3.6 exp; p<0.01) and peritoneal (52 vs 1.9; p<0.01) malignancies and lung cancer (249 vs 103.1; p<0.01). In women, ovarian (9 vs 4.0; p<0.05) and uterine (15 vs 5.8; p<0.01) malignancies were also in excess. No statistically significant increase was found for laryngeal cancer (16 obs vs 12.2 exp). In Poisson regression analyses, the RR of death from pleural neoplasm linearly increased with duration of exposure, while it showed a curvilinear increase with latency and time since cessation of exposure. RR for peritoneal neoplasm continued to increase by latency, duration and time since cessation of exposure. RR for lung cancer showed a reduction after 15 years since cessation of exposure and levelled off after 40 years of latency.

Conclusion: This study of a cohort of asbestos exposed workers with very long follow-up confirmed the reduction in risk of death from lung cancer after the end of exposure. It also suggested a reduction in risk for pleural mesothelioma with over 40 years of latency, while risk for peritoneal mesothelioma showed a continuing increase.

In plain English

This cohort study followed 3434 blue-collar workers of the Eternit asbestos cement plant in Casale Monferrato, Italy. The plant used chrysotile and crocidolite and closed in 1986. Deaths in 1965–2003 were compared with Piedmont regional rates. More deaths than expected occurred from all causes (1809 observed vs 1312.3 expected), pleural malignancies (135 vs 3.6), peritoneal malignancies (52 vs 1.9) and lung cancer (249 vs 103.1). Women had more ovarian (9 vs 4.0) and uterine (15 vs 5.8) cancer deaths than expected. The increase for laryngeal cancer (16 vs 12.2) was not statistically significant. Comparing workers within the cohort, lung cancer risk was lower more than 15 years after exposure ended. Even so, among men more than 30 years after exposure ended, lung cancer deaths still exceeded expectations (21 vs 9.6). Pleural cancer risk rose with years of exposure (relative risk 1.05 per year, 95% CI 1.01 to 1.08). Peritoneal cancer risk kept rising with time since first exposure. The authors concluded that lung cancer risk fell after exposure ended and that pleural and peritoneal mesothelioma showed distinct patterns. No individual smoking data were available.

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 of mortality (1965–2003, compared with regional rates) and mesothelioma incidence (compared with regional mesothelioma registry rates), with Poisson regression for comparisons within the cohort
• Who was studied: 3434 blue-collar workers (2657 men and 777 women) at the Eternit asbestos cement plant in Casale Monferrato, Piedmont, Italy, who were active on 1 January 1950 or hired between 1950 and 1986
• Exposure: Asbestos cement production (plain and corrugated sheets, chimney tubes, high-pressure pipes) using chrysotile and crocidolite; duration of employment in the factory was used as the measure of exposure
• Main results:
  • Whole cohort (men and women): deaths from all causes were higher than expected, 1809 observed vs 1312.3 expected
  • Whole cohort: pleural malignancy deaths 135 observed vs 3.6 expected; peritoneal malignancy deaths 52 vs 1.9 (both p less than 0.01)
  • Whole cohort: lung cancer deaths 249 observed vs 103.1 expected
  • Lung cancer standardised mortality ratio was 242.5 among men and 220.5 among women
  • Women: ovarian cancer deaths 9 observed vs 4.0 expected; uterine cancer deaths 15 vs 5.8
  • Whole cohort: laryngeal cancer deaths 16 observed vs 12.2 expected, not a statistically significant increase
  • Asbestosis was the underlying cause of death for 162 men and 24 women
  • Pleural malignant mesothelioma incidence: standardised incidence ratio 3447 in men (37 observed vs 1.07 expected) and 5952 in women (12 observed vs 0.20 expected)
  • Peritoneal malignant mesothelioma incidence: standardised incidence ratio 17 805 in men (18 observed vs 0.10 expected) and 18 592 in women (5 observed vs 0.03 expected)
  • Pleural neoplasm, within-cohort Poisson regression: relative risk 1.05 (95% CI 1.01 to 1.08) per year of exposure
  • Pleural neoplasm: the latency pattern suggested a reduction in relative risk after 50 years of latency, with wide confidence intervals
  • Pleural neoplasm: a trend toward lower risk more than 15 years after exposure ended was not statistically significant
  • Peritoneal neoplasm: the trend with latency was steeper than for pleural mesothelioma, with no sign of lower risk after long latency or long time since last exposure
  • Peritoneal neoplasm: relative risk 11.54 (95% CI 2.80 to 47.64) at 50 or more years of latency, compared with 20–29 years
  • Lung cancer, within-cohort Poisson regression: compared with 3–15 years after exposure ended, risk was lower at 15–30 years (RR 0.70, 95% CI 0.52 to 0.95) and at more than 30 years (RR 0.56, 95% CI 0.35 to 0.92)
  • Men: lung cancer standardised mortality ratio more than 30 years after the end of exposure was still 217.8 (21 observed vs 9.6 expected)
  • Lung cancer relative risk was about eightfold higher in men than in women (RR 8.34, 95% CI 4.63 to 15.11), which the authors considered likely to reflect smoking
• The authors' conclusion: The authors concluded that their analyses indicate a reduction in lung cancer risk after exposure ends and confirm the role of duration of exposure in pleural mesothelioma. They also concluded that pleural and peritoneal mesothelioma show distinct risk patterns after long latency, with risk increasing for peritoneal but not for pleural mesothelioma.
• Limitations the authors state:
  • No individual smoking information was available
  • The separate roles of chrysotile and crocidolite could not be distinguished
  • There were not enough measurement data to estimate individual cumulative doses; duration of employment was used instead
  • Poisson regression relative risks compare workers within the cohort, all of whom were exposed, not with unexposed people
  • Asbestos exposure in other jobs could not be excluded
  • No clinical record was available to review the diagnosis in 5 of the 15 uterine cancer cases

Topics

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

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Cohort Study, Asbestos-Cement, Mesothelioma, Eternit, Lung Cancer, Laryngeal Cancer, Neoplasm.

Related studies

• Cohort study of workers employed in an Italian tire manufacturing plant, 1962-2004 — D. Mirabelli, A.M. Cacciatore, 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)
• 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)
• Mortality in asbestos cement workers in Pavia, Italy: A cohort study — E. Oddone, D. Ferrante, et al. (2017)
• Absence of radiographic asbestosis and the risk of lung cancer among asbestos-cement workers: Extended follow-up of a cohort — M.M. Finkelstein (2010)

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