| Budget Amount *help |
¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 2000: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1999: ¥1,700,000 (Direct Cost: ¥1,700,000)
|
|---|
| Research Abstract |
The issue as to whether exposure to chrysotile asbestos alone, without amphibole asbestos contamination, causes lung cancer and mesothelioma was investigated a 25 years longitudinal study undertaken in Chongqin, China between January 1, 1972 and December 31, 1996. The study cohort comprised 515 male workers exposed to chrysotile only and the control cohort 650 non-dust exposed workers. The results of analysis by proportional hazard model indicate that mortality due to all causes, total cancer, and lung cancer were related to asbestos exposure. The relative risks (RR) adjusted for age and smoking were 2.9, 4.3, and 6.6, respectively. Fiber concentration in the raw material section was 7.6 fiber per milliliter (f/ml) and that in the textile section was 4.5 f/ml. Because of differences between study and control plants, comparisons were also made between various sections within the asbestos plant with different dust exposure. Adjusted RR for lung cancer of high exposed workers compared to low exposed workers was 8.1. Two cases of malignant mesothelioma, one pleural and the other peritoneal with latency peiods of 13.8 years and 21.8 years repectively, were found in the asbestos cohort. These results suggest that heavy exposure to pure chrysotile asbestos alone, with negligible amphibole contamination, can cause lung cancer and malignant mesothelioma in exposed workers. Studies to confirm the above findings has been planned using other groups of asbestos exposed population in China and in Vietnam. Preliminary study in Vietnam has been started.
|
