Persistent organic pollutants such as polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and organochlorine pesticides (OCPs) are of global concern because of their widespread contamination and adverse health effects. Potential endocrine disruption, especially of thyroid status by PCBs has been repeatedly suggested in both experimental and epidemiological studies. However the associations with PBDEs or OCPs have been arguable especially in human populations. We investigated the associations between major groups of POPs and thyroid hormone balances among pregnant women. One hundred thirty eight pregnant women at delivery were recruited from four cities of Korea in 2011. Blood samples were collected within a day before delivery. Serum was then analyzed for 19 PCBs, 19 PBDEs, and 19 OCPs, along with five thyroid hormones (free and total T3 and T4, and TSH). Several PCBs such as PCB28,118,138, or 153 showed either negative associations with T3 or T4, or positive associations with TSH. BDE47 and total PBDEs showed negative associations with T3 or T4, or positive associations with TSH, even when the effects of PCBs were adjusted. For OCPs, while the associations were rather inconsistent and insignificant, chlordanes (CHDs) and hexachlorobenzene (HCB) were generally associated with reduction of T3 or T4, or increase of TSH. Although the thyroid hormone levels of all the subjects were within the reference range, exposure to PCBs and PBDEs were clearly related with potential for disrupting thyroid hormone balance among pregnant women, at the current level of exposure. Although subtle, the changes in thyroid hormones should be seen with caution because even minor changes within pregnant women may have significant consequences especially on sensitive population like fetus.
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