Effects of low-level prenatal exposure to dioxins on cognitive development in Japanese children at 42 months

Background: Prenatal exposure to polychlorinated dibenzo-p-dioxins (PCDDs) or polychlorinated dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (dioxin-like compounds [DLCs]) through environmental chemicals may affect the neurodevelopment of children. In our previous study, an inverse association was observed between prenatal DLCs and neurodevelopment of infants aged 6 months in both sexes. However, studies are yet to determine how long these adverse effects last. Objective: To examine whether the effects of DLCs on cognitive development remains at 42 months. Methods: In this prospective cohort study conducted in Sapporo, Japan, pregnant mothers' blood was analyzed for the congener level of DLCs. The Kaufman Assessment of Battery for Children (K-ABC) was used to test their children's cognitive development at 42 months. A total of 141 mother-child pairs were included in the final analysis. The multiple linear regression analysis was used to examine the association between the K-ABC scores and DLC levels in the maternal blood. Results: Seven isomers (1,2,3,6,7,8-HxCDD, 2,3,4,7,8-PeCDF, 33'44'55'-HxCB(#169), 2344'5-PenCB(#114), 233'44'5-HexCB(#156), 233'44'5'-HexCB(#157), 23'44'55'-HexCB(#167), total PCDF, and TEQ-PCDD, PCDF, PCDD/DFs levels were positively associated with the achievement score (AS) of K-ABC. However, total non-ortho PCBs were negatively associated with the Mental Processing Composite Score (MPCS) of K-ABC in males. In females, increased TEQ-dl PCB and TEQ-PCDD/F/dl-PCB were also associated with increasing AS score. Conclusions: This study suggests that the negative effects of prenatal DLC exposure on children's cognitive development at 6 months were not observed in children aged 42 months. Regarding the sex-specific effects, AS and DLC swere positively correlated in females, whereas those of MPCS and DLCs were significantly negative inmales. (C) 2017 Elsevier B.V. All rights reserved.