Cancer mortality in a cohort of asbestos textile workers

Our plain-English summary of Cancer mortality in a cohort of asbestos textile workers, by E. Pira, C. Pelucchi, L. Buffoni, et al (British Journal of Cancer, 2005).

The study

• Authors: E. Pira, C. Pelucchi, L. Buffoni, A. Palmas, M. Turbiglio, E. Negri, P.G. Piolatto, C. La Vecchia
• Journal: British Journal of Cancer
• Published: 2005;92(3):580-6
• Cited by: 78 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

A cohort of 889 men and 1077 women employed for at least 1 month between 1946 and 1984 by a former Italian leading asbestos (mainly textile) company, characterised by extremely heavy exposures often for short durations, was followed up to 1996, for a total of 53,024 person-years of observation. Employment data were obtained from factory personnel records, while vital status and causes of death were ascertained through municipality registers and local health units. We observed 222 cancer deaths compared with 116.4 expected (standardized mortality ratio, SMR=191). The highest ratios were found for pleural (SMR=4105), peritoneal (SMR=1817) and lung (SMR=282) cancers. We observed direct relationships with duration of employment for lung and peritoneal cancer, and with time since first employment for lung cancer and mesothelioma. Pleural cancer risk was independent from duration (SMR=3428 for employment <1 year, 7659 for 1-4 years, 2979 for 5-9 years and 2130 for > or =10 years). Corresponding SMRs for lung cancer were 139, 251, 233 and 531. Nonsignificantly increased ratios were found for ovarian (SMR=261), laryngeal (SMR=238) and oro-pharyngeal (SMR=226) cancers. This study confirms and further quantifies the central role of latency in pleural mesothelioma and of cumulative exposure in lung cancer.

In plain English

This cohort study followed 1,966 workers (889 men, 1,077 women) employed at least one month during 1946 to 1984 at a mainly textile asbestos company near Turin. Several asbestos types were used, including crocidolite. Deaths to the end of 1996, or age 80 if earlier, were compared with Italian national rates (standardized mortality ratio, SMR; 100 means as expected). There were 222 cancer deaths against 116.4 expected (SMR 190.7, 95% confidence interval 166 to 218). Ratios were highest for pleural (23 deaths, SMR 4105.5, interval 2603 to 6158), peritoneal (14 deaths, SMR 1817.2, interval 992 to 3053) and lung cancer (76 deaths, SMR 282.4, interval 222 to 354). Asbestosis accounted for 38 deaths. Lung cancer SMR rose with employment length, from 139.1 (under one year) to 530.9 (ten years or more). Pleural cancer SMR did not; six of its 23 deaths followed under a year's employment. Ovarian, laryngeal and oral-pharyngeal excesses were not statistically significant. The authors judged the pleural SMR probably overestimated. They concluded that time since first employment (latency) was central to mesothelioma risk, and cumulative exposure to lung cancer risk.

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 Italian national death rates (standardized mortality ratios), with multiplicative and additive models for mesothelioma
• Who was studied: 1966 workers (889 men, 1077 women) employed at least 1 month between 1946 and 1984 at an asbestos, mainly textile, company in Grugliasco near Turin, Italy. They were followed to 31 December 1996 or to age 80 if that came earlier, for 53 024 person-years. Seven of 1973 workers were excluded for missing dates.
• Exposure: Work in an asbestos textile factory where various asbestos types, including crocidolite, were used. Measured dust levels in carding reached 100 fibres per cubic centimetre in the late 1960s and 25 in the early 1970s.
• Main results:
  • Whole cohort: 222 cancer deaths observed against 116.4 expected (SMR 190.7, 95% CI 166 to 218)
  • Pleural cancer, whole cohort: 23 deaths, SMR 4105.5 (95% CI 2603 to 6158). Men: 12 deaths, SMR 2851.5. Women: 11 deaths, SMR 7891.2.
  • Peritoneal cancer, whole cohort: 14 deaths, SMR 1817.2 (95% CI 992 to 3053)
  • Lung cancer, whole cohort: 76 deaths, SMR 282.4 (95% CI 222 to 354)
  • Pleural, peritoneal and lung cancer SMRs were higher in women than in men
  • 38 deaths were attributed to asbestosis
  • Lung cancer SMR rose with duration of employment, from 139.1 for less than 1 year to 530.9 for 10 years or more
  • Pleural cancer SMR did not rise with duration of employment: 3427.7 for less than 1 year, 7659.3 for 1 to less than 5 years, 2978.6 for 5 to less than 10 years, and 2129.9 for 10 years or more
  • Six of the 23 people who died of pleural cancer had worked at the company less than 1 year, and three of them less than 4 months
  • 12 pleural cancer deaths occurred 25 years or more after first employment, against 0.3 expected
  • In models fitting time-related factors together, latency (time since first employment at the factory) was the main determinant of mesothelioma risk, with no significant trend by duration of employment
  • Ovarian cancer, women: 5 deaths, SMR 261.4 (95% CI 85 to 609). The confidence interval includes 100.
  • Laryngeal cancer: 7 deaths, all men, SMR 238.0 for the whole cohort (95% CI 95 to 490). The confidence interval includes 100.
  • Oral and pharyngeal cancer: 7 deaths, all men, SMR 225.6 for the whole cohort (95% CI 90 to 465). The confidence interval includes 100.
  • No excess of kidney cancer was found (SMR 98)
• The authors' conclusion: The authors concluded that the study adds quantitative information on mesothelioma and lung cancer risks in textile workers. In their view, latency (analysed as time since first employment at the factory) is central to mesothelioma risk, and cumulative exposure is central to lung cancer risk. They noted an over 30-fold excess of pleural cancer even in workers exposed for less than a year.
• Limitations the authors state:
  • The pleural cancer SMR is probably overestimated because national rather than local rates were used. Correcting for Turin province rates would give about 2200.
  • Only date of death, not date of diagnosis, was available
  • Time since first and time since last employment were highly correlated, so their separate effects could not be disentangled
  • Smoking and alcohol information was not available for most subjects, so higher consumption in the cohort could not be excluded as an explanation for laryngeal and oro-pharyngeal results
  • Raised intestinal cancer ratios might reflect misdiagnosed peritoneal mesothelioma
  • Three mesothelioma cases had earlier job-related asbestos exposure, so risks for a late age at first exposure may be somewhat overestimated

Topics

Medical terms in this study, explained in our Lexicon: standardized mortality ratio (SMR), Lung Cancer, Mesothelioma, Latency, Pleural Mesothelioma, Cumulative Exposure.

Related studies

• Mortality from cancer and other causes in the Balangero cohort of chrysotile asbestos miners — E. Pira, C. Pelucchi, et al. (2009)
• Updated mortality study of a cohort of asbestos textile workers — E. Pira, C. Romano, et al. (2016)
• 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)
• 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)
• Tyler asbestos workers: mortality experience in a cohort exposed to amosite — J.L. Levin, J.W. McLarty, et al. (1998)
• Mortality among workers in the geothermal power plants at Larderello, Italy — E. Pira, M. Turbiglio, et al. (1999)

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