The Pollution Characteristics And Health Risk Assessment Of Polycyclic Aromatic Hydrocarbons And Their Derivatives In The Plasma Of Oilfield Workers

Polycyclic aromatic hydrocarbons(PAHs)and their derivatives(MPAHs,OPAHs)are persistent organic pollutants widely existing in the environment.They are byproducts of incomplete combustion of fossil fuels or biomass,and have strong teratogenic,carcinogenic and mutagenic toxicity.At present,studies on PAHs and its derivatives at home and abroad mainly focus on environmental media.Due to the limitation of applicability of these data,they cannot reflect the real exposure level.By contrast,internal exposure is more accurate and authentic by measuring the concentration of contaminants in body fluids or tissue fluids.The study of the exposure characteristics of pa Hs in human body is helpful to evaluate the burden and potential toxic effects of these substances on human body.A total of 19 Chinese workers who worked abroad in an oilfield in Iraq were enrolled in this study.Blood samples were collected twice in pre-and post-workshift,and the physical examination information(blood routine index)of the participating workers was statistically sorted out.The concentrations of PAHs in human plasma were measured using gas chromatograph-mass spectrometer instrument(GC-MS).The mt DNA methylation levels of specific DNA fragments(COX1,COX2,COX3,ATP6,ATP8)were detected by polymerase chain reaction(PCR)and pyrosequencing.According to the exposure level and characteristics of oilfield workers,the relationship between exposure response and mitochondrial DNA methylation level(biomarkers)and blood routine indexes(physiological indexes)was explored.Furthermore,based on the pharmacokinetic model,we estimated the total estimated daily intake(TEDI)of humans by serum PAHs levels.toxic equivalence factors(TEFs)were used to calculate toxic equivalence quantities(TEQs)of PAHs in the plasma for quantifying the toxic potential of PAHs and further evaluating the cancer risk of human exposure to PAHs.Six PAHs,two MPAHs and one OPAH were detected in the plasma samples.The concentrations of PAHs,MPAH and OPAHs were 31.4ng/m L,2.7 ng/m L and 7.2ng/m L in post-workshift,and 48.6ng/m L,4.5 ng/m L and 8.7 ng/m L in post-workshift,respectively.Linear regression analysis indicated a statistically significant relationship between PAHs levels with methylation levels and blood routine indexes.The exposure reaction between PAHs and mt DNA methylation,Ant showed a significant positive correlation with COX1 methylation.Flo and Phe were positively correlated with COX3methylation.Dibf was negatively correlated with ATP6 methylation.There was also a significant negative correlation between Nap-2 and ATP8 methylation.The study on the exposure-response relationship of PAHs(include derivatives)with mt DNA methylation in the plasma of oilfield workers,we found that Ant could induce up-regulation of the mt DNA methylation of COX1,and Flo and Phe could induce up-regulation that of COX3,respectively,Dibf could induce down-regulation of the mt DNA methylation of ATP6,Nap-2 could induce down-regulation of the mt DNA methylation of ATP8.The relationship between PAHs(include derivatives)and blood routine indexes,Nap-2 could induce down-regulation of white blood cell count,Ant and Flu could induce up-regulation of white blood cell count.Dibf could induce down-regulation of erythrocyte,Ant could induce up-regulation of erythrocyte.Dibf ould induce down-regulation of hemoglobin.The results of this study were compared with those of domestic and foreign researches,indicating that there are risks of genetic changes and blood system disorders in oilfield workers.Health assessment using the cancer risk model showed the CR values were between 10^-4 and 10^-6in pre and post-workshift,indicating the potential carcinogenic risk of PAHs and its derivatives in plasma.