A study on lymphocyte DNA damage in traffic policemen in Guangzhou

OBJECTIVE: To study the effect of occupational exposure to traffic exhaust and smoking on DNA damage in traffic policemen. METHODS: 812 traffic policemen (741 men and 71 women, 130 of office-work and 682 of outside work) from 8 districts in Guangzhou were investigated. Blood samples were taken by venipuncture and lymphocytes were collected by using lymphocyte separation medium and centrifugation. The comet assay was used to measure DNA damage. RESULTS: The office-work policemen [(37.7 +/- 9.5) years] were older than the outside-work ones [(32.3 +/- 8.1) years, P < 0.001]. No significant difference was observed in sex (P = 0.08) and age (P = 0.45). Comet assay showed that occupational exposure to traffic exhaust significantly increased tail length [4.20 micro m, 95% CI: (3.98 - 4.42) micro m vs 3.23 micro m, 95% CI: (2.82 - 3.7) micro m, P < 0.001]. Smokers had longer tail length [4.66 micro m, 95% CI: (4.37 - 4.97) micro m] than ex-smokers [3.28 micro m, 95% CI: (2.57 - 4.17) micro m] and nonsmokers [3.47 micro m, 95% CI: (3.21 - 3.75) micro m, P < 0.001]. In nonsmokers, significant increase in tail length was observed by passive smoking at home (P = 0.004) but not at work (P = 0.22). When out-door nonsmokers were excluded, passive smoking at work also significantly increased tail length (P = 0.007). Analysis of covariance showed that occupational exposure to traffic exhaust, tobacco smoking, and female had independent effect on lymphocyte DNA damage (P < 0.001) after these factors were adjusted. Passive smoking and age had no effect on lymphocyte DNA damage. CONCLUSIONS: Occupational exposure to traffic exhaust and tobacco smoking respectively increase lymphocyte DNA damage. Female traffic policemen may have more severe DNA damage than male.