Study on the exposure of polychlorinated biphenyl contamination and DNA methylation in male employees in an e-waste dismantling area in Tianjin

Abstract

Objective: To study on the exposure of polychlorinated biphenyl (PCB) contamination and DNA methylation in male employees in an e-waste dismantling area in Tianjin. Methods: In 2016, an e-waste dismantling area in Tianjin and an area 50 km away from the e-waste dismantling area (no e-waste or other chemical, industrial and agricultural pollution nearby) were selected as the study area and the reference area. Male residents of the study area and male farmers who planted vegetables, fruits, and crops in the reference area were selected as the exposed and reference group by using the convenient sampling method. A total of 60 subjects (30 in each of the exposed group and the reference group) were included. The peripheral blood (5 ml) of the study subject was collected, and the PCB concentration was detected. Eight independent subjects in the exposed group and the reference group were randomly selected by random number table method to detect the methylation level of the promoter region of all gene loci, and the mRNA transcript levels. Results: The PCB concentration in peripheral blood of the exposed group was higher than that of the reference group, and the difference was statistically significant (allP values <0.001). The methylation levels of the promoter region of the exposed group and the reference group showed obvious clustering, and 994 gene loci had different degrees of methylation. Compared with the reference group, there were 391 hypomethylation sites and 553 hypermethylation sites in the exposed group. The proportion of methylation sites in the high CpG-rich region was 59.2% and 48.1%, respectively. The mRNA level of the hypomethylated gene in the exposed group was higher (FAM131A, HBM), and the transcription level of the hypermethylated gene was lower (CAPN15, NFIC, SHISA5, FGF13, GRAMD1A, CLEC3B, LILRB2, DCAF7). The mRNA transcription levels of 10 genes above in the exposed group and the reference group were statistically significant (all P values <0.001). Conclusion: The PCB concentration of peripheral blood in the exposed population of e-waste is high. PCB exposure changes the methylation level of specific genes and affects the mRNA transcription level of some genes.