Study On Biomarkers Of DNA Damage For Monitoring The Genotoxic Effect Of Benzene, PM_2.5 And PAHs Exposure

The aim of this study was to assess the exposure to benzene,PM_2.5 and polycyclic aromatic hydrocarbons(PAH_S) associated with PM_2.5,and to explore the biomarkers of effect and susceptibility that could be used in monitoring the genotoxic effect of ambient air pollution.Methods1.In June 2007,Sixty-two traffic policemen and thirty-five male suburban inhabitants were selected.The information on smoking,drinking alcohol, exercising habit and so on was investigated by questionnaire.2.The exposure levels of benzene,PM_2.5 and PAHs associated with PM_2.5 were assessed by both ambient air monitoring and exposure biomonitoring.The atmospheric air samples were collected within two consecutive days in the work place of traffic policeman and in the residential area of suburban inhabitants respectively.The benzene concentrations were determined by thermal desorption-gas chromatography,while the PAHs concentrations were determined by high performance liquid chromatography(HPLC).As internal dose,the 1-hydroxylpyrene(1-OHP) of pyrene metabolite and S-phenylmercapturic acid (S-PMA) of benzene metabolite were determined by HPLC and ELISA kit respectively.3.As the candidates of genotoxic effect biomarkers,the 8-hydroxydeoxyguanosine (8-OHdG) in the urinary and DNA strand breaks(SB) of peripheral blood lymphocytes were determined by ELISA kit and single cell gel electrophoresis assay(SCGE) respectively.4.As the candidates of susceptibility biomarkers for air pollution,the genetic polymorphisms of glutathione S-transferase M1(GSTM1) and glutathione S-transferase T1(GSTT1) were identified using multiplex polymerase chain reaction(PCR).5.Multiple regression analyses were performed to control the confounding factors and investigate the effect of air pollution and genetic polymorphisms on DNA damage.Results1.The average levels of benzene,PM_2.5 and benzo(a)pyrene(BaP) in the traffic policeman group were 56±36μg/m³,96±38μg/m³,3.20±1.89ng/m³ respectively, while the corresponding values in the suburban inhabitant group were 24±17μg/m³,45±22μg/m³,1.54±0.76 ng/m³ respectively.The concentrations of urinary 1-OHP and S-PMA in traffic policeman group were 3.83±3.39μmol/mol creatinine and 0.56±0.48μmol/mol creatinine respectively,which were significant higher than the corresponding values in the suburban inhabitant group: 2.42±2.63μmol/mol creatinine and 0.33±0.28μmol/mol creatinine(P＜0.05).2.The concentrations of urinary 1-OHP and S-PMA were both significantly positive correlated with the urinary 8-OHdG.After adjusting for confound factors,the correlation between S-PMA and 8-OHdG was still significant(P＜0.01).3.No influence of air pollution and other investigated factors on the levels of DNA strand breaks was found.4.No influence of GSTM1 and GSTT1 genotype on the levels of urinary 8-OHdG or DNA strand break was found.ConelusionBoth the environmental air pollutant monitoring and internal dose measurement indicated that traffic policemen exposed to higher level of air pollutants than the control group.The urinary 8-OHdG might be an early genotoxic effect biomarker of air pollution.The DNA strand breaks were not a sensitive genotoxic effect biomarker of air pollution.Whether genetic polymorphism of GSTM1 and GSTT1 could be used as biomarkers of susceptibility for ambient air pollutants exposure still needs further study.