Cancer mortality in a cohort of asbestos textile workers

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 ¼ 191). The highest ratios were found for pleural (SMR ¼ 4105), peritoneal (SMR ¼ 1817) and lung (SMR ¼ 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 ¼ 3428 for employment o1 year, 7659 for 1 -4 years, 2979 for 5 -9 years and 2130 for X10 years). Corresponding SMRs for lung cancer were 139, 251, 233 and 531. Nonsignificantly increased ratios were found for ovarian (SMR ¼ 261), laryngeal (SMR ¼ 238) and oro-pharyngeal (SMR ¼ 226) cancers. This study confirms and further quantifies the central role of latency in pleural mesothelioma and of cumulative exposure in lung cancer.

First and subsequent asbestos exposures in relation to mesothelioma and lung cancer mortality

“…For lung cancer, the SMR only changed modestly from 282 to 310 over the last 8 years considered. The appreciable fall in asbestos exposures since the early 1970s in the factory (Pira et al, 2005) and the cessation of exposure in 1984 may have contributed to this levelling of lung cancer risk, and further supports the view that time-related factors involved in mesotheliomas and lung cancers differ. When we stratified our data according to the period at first employment, direct trends emerged with latency.…”

“…As compared to the 1996 follow-up (Pira et al, 2005), in this updated analysis there were 31 additional deaths from pleural and peritoneal mesothelioma (total 68), and 29 additional deaths from lung cancer (total 109), allowing examination of the role of first and subsequent asbestos exposures in this factory on mesothelioma and lung cancer risk. The SMR of pleural/peritoneal mesothelioma continued to use in the years 1996 -2004, the total number of such deaths having almost doubled.…”

“…Included in the cohort were 1966 subjects (889 males and 1077 females) who had worked in a major asbestos textile factory for at least 1 month in the period from 1946 to 1984, when production ceased (Pira et al, 2005). Various types of asbestos were used in the factory, including crocidolite.…”

“…Models of asbestos-related mesothelioma carcinogenesis also include a direct relation with average exposure to asbestos fibres, and a term for type of asbestos, with risk apparently higher for amphiboles than chrysotile (Boffetta, 1998). The influence of other time-related aspects such as age at first exposure and duration of exposure is largely or totally explained by latency (Peto et al, 1982;Pira et al, 2005), but the role of early and later occupational exposures to asbestos requires further investigation. Recently, fewer deaths from mesothelioma have been reported than predicted on the basis of models of carcinogenesis (Berry et al, 2004;Pelucchi et al, 2004), raising the possibility of a gradual elimination of asbestos from the lungs (Berry et al, 2004).…”

“…We previously examined follow-up data to the end of 1996 from a cohort of nearly 2000 subjects (including more than 1000 women) formerly employed in an Italian asbestos factory (Pira et al, 2005). We have now extended the follow-up to the end of 2004, with 9000 additional person-years of observation allowing us to consider the role of latency, and attempt separation of first from subsequent exposures, in relation to mesothelioma and lung cancer risks.…”