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.

Respiratory symptoms and lung function in jute processing workers: a primary investigation.

This paper presents the results of an investigation of respiratory symptoms and lung function of 404 workers who had been exposed to jute dust in a jute mill. Measurement of total dust concentration and analysis of dust composition were also conducted. Most workers in the jute mill were exposed to jute dusts containing less than 5% silica, whereas a few workers were exposed to dusts containing approximately 10-15% silica. Male smokers and nonsmokers in the dust-exposed group had a higher prevalence of cough and chest tightness compared with those in the control group. Among dust-exposed workers, female nonsmokers had a significantly higher prevalence of cough, chronic bronchitis, chest tightness, and dyspnea than those in the control group. Lung function tests showed that dust-exposed workers had a greater incidence of abnormal lung function than did control workers, as measured by percentage of predicted forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1.0), and FEV1.0/FVC. Dust exposure was the main cause of respiratory symptoms and abnormal values of FEV1.0, but both cigarette smoking and dust exposure contributed to the abnormal values reported for FEV1.0.