Effects Of Trichloroethylene On The Genotoxicity, Oxidative Stress And Health Of Occupationally Exposed Workers

BACKGROUNDTrichloroethylene (TCE) is a voIatiIe organic soIvent which is extensivelyused as a metal degreaser and in many other industriaI processes. Because ofits broad application and potential carcinogenesis, the metabolism and toxicityof TCE have been investigated int6nsively in animals. But, up to now, the datafrom studies on its carcinogenicity and mutagenicity to occupationaIIy exposedworkers have stilI been both very limited and equivocal. Moreover, manyoccupational poisoning events unexpected have already happened infGuangdong province in recent years. So, the studies of the heaIth effects ofTCE exposure and the exploration of reIated preventive measures are an urgentneed.OBJECTlVEThe objectives of the present study is to investigate the effects of TCE onthe heaIth of workers exposed to it, to study the dose-response andtime-response correIations among the exposure IeveI and duration, theexposure indexes (including TCE concentration in the air of workshop,environmental noise Ievel, the leveI of trichloroactic acid (TCA) in urine fromthe workers having been exposed to TCE), and the indexes of earIy biologicaIeffeCt (including the lipid peroxide 1eveI and antioxidase aCtivities in bIood andserum, the frequencies of micronuclei(MN) in the conventionaI nucleated ceIlsand cytochalasin B-blocked binucleated cells, sisterchromatid exchanges(SCE), DNA damage in peripheraI bIood lymphocytes(PBLs), pure tOnehearing threshoIds, and the IeveI of a1-microgIobullin in urine), to explore theeff6Ct of combined exposure Of TCE and noise on pure tone hearingthresholds, to further explore the early sensitive biomarkers and biologicalmonitoring indicators fOr occupationaI injury induced by TCE, and to providescientific basis for working out preventive measurements and revising earlydiagnostic criteria of occupationaI poisoning of TCE.METHODSBased on the labor hygienic investigation and the anaIysis of heaIthstatus of the workers direCtly exposed to TCE in three factories in Zhuhai, theconcentrations of TCE in the air of the workpIace was monitored with gasfchromatography and,the levels of TCA in the workers' urine were det6rminedwith pyridine spectrophotometry. 65 workers exposed to both noise and TCE,and 33 workers exposed to onIy noise, were examined by pure eIectric toneaudiometry (0.5-8 kHz), and noise met6r was used to measure the noise Ievelsof the workshops. 207 workers having been directly and occupationalIy exposedto TCE fOr at least three months were selected as the exposure group, whiIe66 workers who had never been exposed to TCE or other chemical toxicantswere taken as the contro[ group. ln the tWo groups indexes such as sexproportion, age, and smoking habit, etc, were simiIar to each other. 207TCE-exposed workers were divided into three groups based on their exposureIeveIs and years of exposure duration. CAT in peripheral bIood erythrocyte,serum aCtivities of SOD and GSH-Px and MDA, were measured individuaIlywith test boxes. The frequenCy of MN in the conventionaI and cytochalasinB-bIocked binucleated ceIls, fSCE in human peripheral blood lymphocytes(PBLs), and the IeveI of a1-MG in urine were measured. DNA damage wasmeasured by single-ceIl gel electrophoresis (SCGE). The degree of DNAdamage was indexed by the percentage Of lymphocytes with comet-like tail.Hearing damage were assessed by audiometry.RESULTS(1) The averagd concentration of TCE in the workplace in air was 90.4mglm' (ranged 50.3-230.8), higher than the maximum allowable concentrationof national standard (30mglm'). The average levet of urine TCA in the workersexposed to TCE after shiff was 60.74mglL (ranged 5.03-227.5), and 47% ofthem,at levels,were higher than the national Iimit values for occupationaIexposure (50mglL or 0.3mmoIlL).(2) Compared with workers in the control, the activitiy of CAT inerythrocyte, Total-SOD and GSH-Px aCtivities in serum, and serum MDA leve...