Analysis of mortality in chrysotile asbestos miners in China

In order to investigate the mortality of a cohort of chrysotile asbestos miners in China and evaluate its association with exposure to chrysotile, a fixed cohort of 1932 workers in chrysotile asbestos mine was established in 1981 and followed till June 1, 2010. Information on vital status, cause of death and smoking habits was collected. The workers were divided into two groups according to their exposure status. The exposed group was composed of frontline workers who worked directly on mining or processing asbestos products. The control group consisted of those who were not directly exposed to asbestos in their work. Standardized mortality ratio (SMR) was calculated according to Chinese national death rates. Cox proportional hazards model was applied to estimate the adjusted relative risks of deaths from major causes in exposed and control groups. The results of this study showed that main causes of mortality were malignant neoplasm, cardiovascular disease, cerebrovascular disease and respiratory disease for chrysotile miners. The mortality rate was 939.20 per 100 000 person-years for workers. The SMR for all causes of death was 1.46 in the cohort. Statistically significant mortality excesses were found for lung cancer (SMR=1.51), pulmonary heart disease (SMR=2.70), respiratory disease (SMR=1.93), asbestosis (SMR=9.62), and accident (SMR=1.59). The mortalities from malignant neoplasm, lung cancer, cerebrovascular disease and digestive disease in the exposed group were significantly higher than those in the control group. The findings indicate that chrysotile exposure is a risk factor for lung cancer, respiratory disease, cerebrovascular disease and digestive disease.