| Vinyl chloride monomer (CH2=CHC1, VCM) is widely used in industry,95% of them is used in polymerization to polyvinyl chloride (Polyvinyl chloride, PVC), and it is a human carcinogen that has been proven to have multi-organ and multi-system effects, necessitating research regarding the health of VCM-exposed workers. VCM concentration in the workplace air has been strictly controlled throughout the world for its toxicity, but it has reported that VCM could still have health damage under the present permissible exposure limit (PEL) of VCM in china. This indictates that more research is needed to investigate the health effect and genetic toxicity caused by VCM-exposure under this condition.This study evaluated the cumulative exposure dose based on exactly calculated cumulative exposure dose of the workers exposed to VCM. Occupational epidemiological study and molecular biologic technology were performed to investigate the relationship between DNA damage induced by VCM and the cumulative exposure dose by both cross-sectional study and cohort study, and to provide scientific evidence to the early signs of health effect and the mechanism of cancer induced by VCM. At the same time, the DNA repair capacity test based on Cytokinesis-block micronucleus (CBMN) assay was carried out to evaluate the the DNA repair capacity of VCM-exposed workers, to explore the risk of DNA damage induced by VCM, and also to provide scientific evidence to screen susceptible workers and to protect workers exposed to VCM.The VCM in workplace is under the PEL from 1990 to present in this study, but the result of cross-sectional study and cohort study show that VCM can induce DNA damage of workers whose exposure level even lower than the national occupational health standard in China, and there was a dose-response relationship between VCM-exposure and the frequency of MN. 188 VCM-exposed workers are the target population, and 68 workers who did not exposed to VCM are the control population for the cross-section study. The result shows that the frequencies of MN in the exposed group were higher than those of the control group, and there was a dose-response relationship between VCM-exposure and the frequency of MN. In additional, Based on previous prevalence study, a cohort of 43 occupational VCM-exposed workers, whose frequency of MN was normal in 2004, was established to explore the relationship between abnormal frequency of MN and the VCM exposure levels. Until 2010, we found that there are different frequencies of MN between groups of deferent VCM exposure levels. The frequency of MN for group with high VCM exposure levels is significantly higher than those of group with low VCM exposure levels, and the risk is 2.28. And 66 VCM-exposed workers were followed up for 6 years with Cytokinesis-block micronucleus (CBMN) assay in 2004,2007 and 2010 to explore the progress of genetic damage. The result shows that compared with 2004, the frequency of MN significantly increased in 2007 and 2010, and the risk are 1.11 and 1.453. and the abnormal frequency of MN of 2007 and 2010 are both higher than those of 2004, and the risk is 1.15 and 2.45, which point that DNA damage are increasing year by year, and genetic damage induced by VCM is cumulative in the workers. Among all the factors of DNA damage, sex has the effect both on the severity and progress of chromosomal damage. Women had higher MN rates and the changes of both MN rates than men. Therefore, the frequency of MN of peripheral blood lymphocyte can be used as an effective and sensitive biomarker for early DNA damage and follow-up under low-level VCM exposure.Besides, this study focus on the research of the DNA repair capacity of 80 VCM-exposed workers and 30 workers unexposed to VCM. We found that the 3AB index shows the rising tendency with the increasing exposure level, which pointed the VCM exposure can lower DNA repair capacity. Besides, this study shows that DNA repair capacity is a comprehensive indicator with great potential to detect health damage induced by VCM and damage risk of susceptible workers.And in this study, the frequency of MN of middle and high DNA repair capacity group are both lower than those of low DNA repair capacity group, the FR is 0.74 and 0.56, and there was a dose-response relationship between DNA repair capacity and the frequency of MN. It indicates that DNA repair capacity might tightly associate with chromosomal damage induced by VCM. The DNA repair capacity would be worse, and the risk of chromosomal damage induced by VCM could be higher.In conclusion, VCM can induce chromosomal damage even when the exposure level is lower than the national occupational health standard in China; DNA repair capacity might tightly associate with chromosomal damage induced by VCM.
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