Mortality among dust-exposed Chinese mine and pottery workers.
A cohort study of approximately 68,000 persons employed during 1972 to 1974 at metal mines and pottery factories in south central China was conducted to evaluate mortality from cancer and other diseases among workers exposed to different levels of silica and other dusts. A follow-up of subjects through December 31, 1989 revealed 6,192 deaths, a number close to that expected based on Chinese national mortality rates. There was, however, a nearly 6-fold increase in deaths from pulmonary heart disease (standard mortality ratio, 581; 95% confidence interval 538 to 626), and a 48% excess of mortality from nonmalignant respiratory diseases (standard mortality ratio, 148; 95% confidence interval, 139 to 158), primarily because of a more than 30-fold excess of pneumoconiosis. Pulmonary heart disease and noncancerous respiratory disease rates rose in proportion to dust exposure. Cancer mortality overall was not increased among the miners or pottery workers. There was no increased risk of lung cancer, except among tin miners, and trends in risk of this cancer with increasing level of dust exposure were not significant. Risks of lung cancer were 22% higher among workers with than without silicosis. The findings indicate that respiratory disease continues to be an occupational hazard among Chinese miners and pottery workers, but that cancer risks are not as yet strongly associated with work in these dusty trades.