Association of low-dose exposure to persistent organic pollutants with global DNA hypomethylation in healthy Koreans

BACKGROUND: Global DNA methylation levels have been reported to be inversely associated with blood levels of persistent organic pollutants (POPs), xenobiotics that accumulate in adipose tissue. Whether these associations extend to a population with much lower concentrations of POPs is not known. OBJECTIVES: This study was performed to examine whether low-dose exposure to POPs was associated with global DNA hypomethylation in Koreans. METHODS: The amount of global DNA hypomethylation was estimated by the percent 5-methylcytosine (%5-mC) in Alu and LINE-1 assays in 86 apparently healthy Koreans. Among various POPs, organochlorine (OC) pesticides, polychlorinated biphenyls (PCBs), and polybrominated diphenylethers (PBDEs) were measured. RESULTS: Most OC pesticides were inversely and significantly associated with %5-mC in the Alu assay, with correlation coefficients in the range -0.2 to -0.3 after adjusting for age, sex, body mass index, smoking, and alcohol. The strongest OC pesticide associations with %5-mC in the Alu assay were observed with oxychlordane, trans-nonachlor, and p,ṕ- dichlorodiphenyldichloroethylene. The correlation coefficient of age with %5-mC in the Alu assay was -0.24, similar to correlations of OC pesticides with %5-mC in the Alu assay. Most PCBs and PBDEs showed nonsignificant inverse trends with %5-mC in the Alu assay, but for some PCBs the U-shaped association was significant. On the other hand, POPs were not associated with %5-mC in the LINE-1 assay. CONCLUSIONS: We found that low-dose exposure to POPs, in particular OC pesticides, was associated with global DNA hypomethylation in apparently healthy Koreans.