Mortality from occupational exposure to relatively pure chrysotile: a 39-year study.

BACKGROUND: Asbestos exposure is related to serious adverse health effects. However, there is disagreement about the relationship between chrysotile exposure and mesothelioma or lung cancer.

OBJECTIVES: Our aim was to investigate the mortality rate among workers exposed to relatively pure chrysotile in an asbestos cement factory.

PATIENTS AND METHODS: In an asbestos cement plant opened in 1968, we prospectively studied all 317 workers. A quantity of 2,000 tons of chrysotile, with minimal amphibole contamination, was used annually until 1 January 2005. Asbestos fiber concentration was measured regularly. Date and cause of death were recorded among active and retired workers.

RESULTS: Asbestos fiber concentration was always below permissible levels. Fifty-two workers died during the study. The cause was cancer in 28 subjects; lung cancer was diagnosed in 16 of them. No case of mesothelioma was reported. Death was attributed to cardiovascular diseases in 23 subjects and to liver cirrhosis in 1. Overall mortality rate was significantly lower than that of the Greek general population, standardized mortality ratio (SMR) was 0.71 (95% CI 0.53-0.93). Mortality due to cancer was increased (SMR 1.15, 95% CI 0.77-1.67), mainly due to lung cancer mortality (SMR 1.71, 95% CI 0.98-2.78), but not significantly.

CONCLUSIONS: Occupational exposure to relatively pure chrysotile within permissible levels was not associated with a significant increase in lung cancer or with mesothelioma. Decreased overall mortality of workers indicates a healthy worker effect, which--together with the relatively small cohort size--could have prevented small risks to be detected.