The effect of occupational exposure and smoking on mortality——a prospective cohort study on 165 660 workers in Guangzhou,China

Abstract

Objective To study the effects of exposure to occupational hazards and smoking on mortality. Methods Based on the Guangzhou Occupational Health Surveillance Record System established in 1989～1992,165 660 factory workers and drivers(aged≥30)were included.Baseline information was retrieved from individual health records onto computer by Intelligent Character Recognition technology.Vital status and causes of death were followed up until 31 December 1998. RR (95% CI ) were calculated and survival curves for occupational exposure and smoking were developed with Cox proportional hazards models by SPSS 10.0. Results There were 165 660 subjects(129 155 men,36 505 women) in the study with mean age of (42.0±6.3)years,and 87% of them were 30～49.Of them,37.3% had been exposed to occupational hazards.In men,70.8% of factory workers and 54.8% of drivers were smokers,but only less than 2.0% of the women had ever smoked in.The mean follow up time was (7.6±1.1)years with 1 252 168 person years in total 2 437 subjects died during the time,51(2.1%) of whom had unknown cause of death.Crude death rates were 194.6 per 100 000 person year for all subjects with factory workers 241.5 per 100 000 person year,drivers 143.1 per 100 000 person year,all men 225.0 per 100 000 person year and all women 92.6 per 100 000 person year.For occupational exposure,significant adjusted RR (95% CI ) of deaths from total causes,stroke,and other causes were 1.11(1.02～1.20),1.30(1.01～1.68) and 1.27(1.06～1.51);and for smoking, RR (95% CI ) of deaths from total causes,malignant neoplasms and lung cancer were 1.23(1.11～1.35),1.34(1.16～1.54) and 2.51(1.81～3.48),respectively.Higher risks were observed in smokers with occupational exposure,showing RR (95% CI ) of 1.32(1.16～1.68) for all causes and 1.35 (1.12 ～1.62) for malignant neoplasms.Furthermore,the RR of all causes,malignant neoplasms,lung cancer and stomach cancer increased with the increasing of pack years of smoking( P 0.01). Conclusion Mortality in workers is associated with both occupational exposure and smoking,and the risk is higher for smokers.The highest risk is observed when both factors are present simultaneously.