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

We analysed data from a cohort of 1966 subjects (889 men and 1,077 women) employed by an Italian asbestos (mainly textile) company in the period 1946-1984, who were followed-up to 2004. A total of 62,025 person-years of observation were recorded. We computed standardised mortality ratios (SMR) for all causes and selected cancer sites using national death rates for each 5-year calendar period and age group. There were 68 deaths from mesothelioma (25 men and 43 women, 39 pleural and 29 peritoneal) vs 1.6 expected (SMR=4,159), and 109 from lung cancer vs 35.1 expected (SMR=310). The SMRs of pleural/peritoneal cancer were 6661 for subjects exposed only before 30 years of age, 8,019 for those first exposed before 30 and still employed at 30-39 years of age and 5,786 for those first exposed before 30 and still employed at 40 or more years of age. The corresponding SMRs for lung cancer were 227, 446 and 562. The SMR of mesothelioma was strongly related to time since first exposure. The SMR of lung cancer, but not of mesothelioma, appeared to be related to subsequent exposures.