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

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.