The prevention of silicosis and prediction of its future prevalence in China.

We studied the effects of preventive and therapeutic interventions on the 18-year cumulative incidence of silicosis of 26,603 dust-exposed workers in seven Chinese mines and industrial plants. Cumulative silicosis incidence decreased from 36.1 percent in workers employed before 1950 to 1.5 percent in workers employed after 1960. From the 1950s to 1970s, eight-year cumulative incidence of tuberculosis decreased from 54.7 percent to 16.7 percent and case fatality of silicosis patients dropped from 53.9 percent to 18.3 percent. From 1950s to 1980s, the average age at the detection of silicosis increased from 41.3 to 52.7 and the average survival time of silicosis patients prolonged from 2.0 to 12.2 years. Workers over age 40 who began exposure to dust before 1960 will be the main source of new silicosis patients in future. Most expected new cases of silicosis will occur within the next 15 years. The silicosis population will remain unchanged for the next 20 years and will decrease dramatically after 25 years. There will be few silicosis patients in 30 years and new cases of silicosis will be difficult to find in 45 years. These results show that the preventive and therapeutic actions against silicosis in China have been effective.