Vinyl chloride monomer (CH2=CHCl, VCM) is a certain human carcinogen and it has been proved to be a multi-organ and multi-system carcinogen. The mechanism of carcinogenesis was presumed to be related to the genetic material damage induced by electrophilic metabolites of VCM. VCM is widely used in industry, 95% of vinyl chloride was polymerized to polyvinyl chloride (PVC). China is one of the important PVC production countries, and its annual production accounts for about 10% of the global production.

This study investigated the relationship between chromosome damage (Cytokinesis-block micronucleus, CBMN) induced by VCM and the cumulative exposure dose of the VCM-exposed workers. At the same time, the DNA repair capacity test based on CBMN assay was carried out to evaluate the DNA repair capacity of the workers.

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 CBMN 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 follow up study on 43 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 was different frequency of MN between groups of different 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. Moreover, 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 and its influencing factors. The result shows that compared with 2004, the frequency of MN significantly increased in 2007 and 2010, and the risk were 1.11 and 1.45, respectively. The abnormal frequencies of MN in 2007 and 2010 are both higher than that of 2004, and the risk were 1.15 and 2.45, respectively, which pointed that the genetic damage are increasing year by year induced by VCM. Among all the influencing factors of DNA damage, gender had the prominent effect both on the severity and progress of chromosomal damage. Female workers had higher MN rates and changes of the both MN rates than male. 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.

The study also focused on the DNA repair capacity of 80 VCM-exposed workers and 30 workers unexposed to VCM, as well as 30 controls. We found that the 3AB index shows the rising tendency with the increasing exposure level, which pointed the VCM exposure can decrease DNA repair capacity, and further increase the chromosomal damage. The results showed that DNA repair capacity was a comprehensive indicator with great potential to detect health damage induced by VCM and damage risk of susceptible workers. Moreover, the frequencies of MN of middle and high DNA repair capacity group are both lower than that of low DNA repair capacity group, the FR is 0.74 and 0.56, respectively. There was a dose-response relationship between DNA repair capacity and the frequency of MN. It indicated 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, so the DNA repair capacity could provide scientific evidence about the risk of chromosomal damage induced by VCM so as to protect the susceptible workers.

In conclusion, VCM can induce chromosomal damage even when the exposure level is lower than the national occupational health standard in China and the VCM exposure can decrease DNA repair capacity. The level of DNA repair capacity may be an important step of the genetic damage induced by VCM. Therefore, the health education and health surveillance should be strengthened so as to protect susceptible workers and improve the quality of working life.

This work was partly supported by the National Natural Science Foundation of China (NSFC81072280),973 program of China (2011CB503801), the Shanghai Bureau of Public Health (grants 08GWD12). We thank physicians Mr. Jun LI, Shuli FENG for their help for physical examination of the workers and data collection of VCM exposure.


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  • Received: 07 May 2012
  • Accepted: 07 May 2012
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