The Influence Of Occupational Exposure To Low Concentration Of Btex On Health And Serum Oxidative Stress Levels Of Gas Station Workers

Objective：Benzene Series(BTEX) is one of the most important classes of organiccompounds, Largely results from human activities, it has been classified into thegroupⅠhuman carcinogen category by the international Agency for Research onCancer（IARC）for carcinogenic, teratogenic and mutagenic effects whichthreatens human health. Most studies suggested that ethyl-benzene has a targetof toxicity for the liver and kidneys, and it also be classified as a suspectedhuman carcinogen by IARC. It has been evidenced that methyl-benzene andxylene have neurotoxicity and embryotoxicity effects. Gasoline contains BTEXthat is leaking during filling fuel in cars. Therefore, it is meaningful to study thestatus and the variation of BTEX on gas station and to study the health damageof BTEX on gas station workers and the biomarkers, in order to prevent the gasstation workers from occupational damage of BTEX effectively at early stage. To detect the concentration of BTEX of human breathing zone in the gasstation, analyze the spatial distribution of the concentration of BTEX and thevariation of the concentration of BTEX one day. The sampling site are located in12gas stations in Nanning; To understand the effect of BTEX on gas stationworkers by health examination; To study influence of BTEX on the serumoxidative stress levels of gas station workers by detecting the levels of serumSOD, GSH, MDA and8-OHDG, and to study influence of BTEX on the DNAdamage of gas station workers by comet assay in peripheral blood lymphocytes；To explore the relationship among markers of oxidative stress, in order toprovide evidence for screening early and sensitive indicators for health damageof BTEX.Methods:1. Chose12gas stations from Nanning city as a research object, usedSUMMA tank collect the air of gas station’s human breathing zone, and usedpre-concentration Entech7100-Chromatography Mass Agilent7890A GC/5975N MSD combined system detect the concentration of BTEX.2. Chose gas station workers from Nanning gas station, who divided intotwo groups to the work area, one is the exposed group mainly includingoperating workers, the other one is control group mainly including stationmasters, card issuing staff, etc. Used the occupational epidemiologicalinvestigation questionnaire to collect the information including the demographicinformation, living habits, occupational history, combined the results on healthexamination of workers to evaluate the health effects of BTEX exposure.3. Chose a sample from gas station workers who participate in healthexamination, divided the sample into the exposed group and the control group.Collected the peripheral venous blood to detect the levels of serum T-SOD, GSH, MDA and8-OHDG by Spectrophotometry or ELISA, and used cometassay of peripheral lymphocyte to detect cell’s injures from BTEX.Results：1.The results of air monitoring showed the average concentration of BTEXper day in all12the gas station’s refueling and non-refueling area of humanbreathing zone, were lower than the national occupational exposure limit.Benzene, methyl-benzene, ethyl-benzene and xylene concentration per day inrefueling area of human breathing zone was60.14g/m3,316.53g/m3,41.51g/m3,211.47g/m3, the concentration per day in non-refueling area ofhuman breathing zone was13.63g/m3,63.22g/m3,9.10g/m3,41.20g/m3.The average concentrations of BTEX in refueling area were higher than innon-refueling area in all12the gas stations, and the average concentrations ofBTEX in afternoon session were higher than morning session at the samesampling point. The order of average concentrations of BTEX in gas station wasmethyl-benzene> xylene>benzene> ethyl-benzene.2. Among all the physical examination results, the abnormal rate of routineurine examination was the highest, the rate was50.9%, followed by abdominalB ultrasound, the abnormal rate was30.8%. The abnormal rates of bloodpressure, ECG and RBC were larger than10%. The abnormal rates of WBC,HGB, PLT, ALT and AST had an upward tendency for exposed group, theaverage values of WBC, RBC and HGB had a downward tendency for exposedgroup, with no significance.3. The results of the anti-oxidative ability showed that the concentration ofT-SOD in exposed group was（42.596.51）U/ml,（49.465.92）U/mlincontrol groups, the difference was statistically significant（P0.001）. Theconcentration of GSH in exposed group was （7.132.73）mg/L, （10.315.36）mg/Lin control groups, the difference was statisticallysignificant（P0.001）.4. The results of the cell’s damage showed that the concentration of MDAin exposed group was （3.251.00） mol/L,（2.320.41） mol/Lin controlgroups, the difference was statistically significan（t P0.001）. The concentrationof8-OHdG in exposed group was （29.7914.13）ng/ml,（20.6010.45）ng/mlin control groups, the difference was statistically significant（P0.001）.Peripheral blood lymphocytes in exposed group showed obvious comet images,comet cells had more long tail, as broom-like; cells and smooth edges in thecontrol group, had no significant tail or short tail, rare comets smearing. Theaverage of TM and OTM in exposed group were （0.0940.170） mand（0.1600.189） m, and the average of TM and OTM in control group were（0.0490.081） mand （0.0990.076） m. Comet tail from the exposed grouphad a growth trend along with working seniority.5. The results of the correlation analysis showed the levels of serum MDAhad a higher relationship of TM, OTM and the levels of SOD, GSH, Spearman’scoefficients were0.28,0.26,-0.21,-0.21. Scatter plot shows that MDA hadbetter discrimination in both exposure group and control group.Conclusion：1. The average concentrations of BTEX per day in gas station were lowerthan the national occupational exposure limit. The levels of BTEX in refuelingarea were higher than in the non-refueling area，it indicated that there was apotential and higher risk of BTEX exposure for operating workers than otherstaff.2. Occupational exposure to BTEX can cause different degrees of healthdamage to workers, mostly on urine, abdominal B, REC, ECG and blood pressure.3. Occupational exposure to BTEX can lead the levels of serum T-SOD,GSH decreased, weakened the anti-oxidative ability.4. Occupational exposure to BTEX can lead the levels of serum MDA,8-OHdG increased, caused the DNA oxidative damage.5. The level of serum MDA could be used as early indicators of healthdamage.