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

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 6months 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 42months.

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 42months. 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 6months were not observed in children aged 42months. Regarding the sex-specific effects, AS and DLCs were positively correlated in females, whereas those of MPCS and DLCs were significantly negative in males.