The associations of prenatal exposure to dioxins and polychlorinated biphenyls with neurodevelopment at 6 Months of age: Multi-pollutant approaches

Abstract

Background: Prenatal exposure to persistent organic pollutants, including polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), dioxin-like polychlorinated biphenyls (DL-PCBs), and nondioxin-like PCBs (NDL-PCBs), has been hypothesized to have a detrimental impact on neurodevelopment. However, the association of prenatal exposure to a dioxin and PCB mixture with neurodevelopment remains largely inconclusive partly because these chemical levels are correlated.

Objectives: We aimed to elucidate the association of in utero exposure to a mixture of dioxins and PCBs with neurodevelopment measured at 6 months of age by applying multipollutant methods.

Methods: A total of 514 pregnant women were recruited between July 2002 and October 2005 in the Sapporo cohort, Hokkaido Study on Environment and Children's Health. The concentrations of individual dioxin and PCB isomers were assessed in maternal peripheral blood during pregnancy. The mental and psychomotor development of the study participants' infants was evaluated using the Bayley Scales of Infant Development-2nd Edition (n = 259). To determine both the joint and individual associations of prenatal exposure to a dioxin and PCB mixture with infant neurodevelopment, Bayesian kernel machine regression (BKMR) and quantile-based g-computation were employed.

Results: Suggestive inverse associations were observed between in utero exposure to a dioxin and PCB mixture and infant psychomotor development in both the BKMR and quantile g-computation models. In contrast, we found no association of a dioxin and PCB mixture with mental development. When group-specific posterior inclusion probabilities were estimated, BKMR suggested prenatal exposure to mono-ortho PCBs as the more important contributing factors to early psychomotor development compared with the other dioxin or PCB groups. No evidence of nonlinear exposure-outcome relationships or interactions among the chemical mixtures was detected.

Conclusions: Applying the two complementary statistical methods for chemical mixture analysis, we demonstrated limited evidence of inverse associations of prenatal exposure to dioxins and PCBs with infant psychomotor development.

Keywords: Bayesian kernel machine regression; Bayley scales of infant development; Birth cohort study; Chemical mixtures; Child health; Dioxins; Neurological development; Persistent organic pollutants; Polychlorinated biphenyls; Polychlorinated dibenzo-p-dioxins; Polychlorinated dibenzofurans; Prenatal exposure; Quantile g-computation.