A prospective cohort study on comparison of risk of death of respiratory system diseases between occupational dust exposure and smoking

OBJECTIVE: To compare the effects of dust exposure and smoking on mortality of respiratory system diseases (RSD). METHODS: Based on the Guangzhou Occupational Health Surveillance Record System established between 1989 and 1992, 80,987 factory workers, aged 30 years old or older, occupationally exposed or not exposed to dusts, were included in a prospective cohort study. RESULTS: (1) The mean age of the cohort was 43.5. Most subjects were workers, had secondary education, and almost all were married. The dust exposure rate was 16.3%, the smoking rate 43.7% and the alcohol-drinking rate 33.5%. (2) The cohort was followed up for 8 years on average, but 35 people (0.04%) were lost for follow up. Among the 1593 deaths, 219 and 90 people died of lung cancer and non-cancer respiratory system diseases (NCRSD) respectively. (3) The adjusted relative risk (RR) of death of lung cancer for smokers, 3.32, was 2.2 times of that for dust exposed workers, 1.53, and the RR of death of NCRSD for dust exposed workers, 2.41, 1.28 times of that for smokers, 1.89, especially for silica dust-exposed workers, 5.72, 3.03 times of that for smokers. Dust exposure combined with smoking caused significantly higher RR of death of RSD. (4) In male, the death risks of RSD were increased with the amount of smoking per day and years of smoking. CONCLUSION: Occupational dust exposure and smoking may cause excessive lung cancer and NCRSD death with synergistic effects. Smoking has higher RR of Lung cancer death than dust exposure. However, the dust exposure contributes to higher RR of NCRSD death. There is a significant dose-effect relationship between smoking and the death risk of RSD.