Lung cancer in asbestos workers with special reference to type of asbestos and preexisting asbestos

2000 Fiscal Year Final Research Report Summary

• Project/Area Number: 11695091
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Public health/Health science
• Research Institution: Teikyo University
• Principal Investigator: NONAKA Koichi Teikyo University School of Medicine Assistant Professor, 医学部, 講師 (80142446)
• Co-Investigator(Kenkyū-buntansha): YANO Eiji Teikyo University School of Medicine Professor, 医学部, 教授 (50114690)
• Project Period (FY): 1999 – 2000
• Keywords: asbestos / chrysotile / lung cancer / mesothelioma / China / Cox proportional hazard model / cohort study / epidemiology

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.