Prenatal dioxin exposure and neurocognitive development in Hong Kong 11-year-old children

Background and objectives: In utero exposure to dioxins and related compounds have been associated with adverse neurocognitive development in infants. It is unclear whether neurodevelopmental deficits persist to childhood. We assessed the association of prenatal dioxin exposure with neurocognitive function in 11-year-old children, and to test whether the association is modified by duration of breastfeeding. Methods: In this prospective study of 161 children born in Hong Kong in 2002, prenatal dioxin exposure was proxied by the dioxin toxicity equivalence (TEQ) in breast milk collected during the early postnatal period as determined by the Chemical-Activated LUciferase gene eXpression (CALUX) bioassay. We used multivariate linear regression analyses to assess the association of prenatal dioxin exposure with the performance on the Wechsler Intelligence Scale for Children-IV, Hong Kong, the Hong Kong List Learning Test, the Tests for Everyday Attention for Children and the Grooved Pegboard Test, adjusting for child's sex, mother's place of birth, mother's habitual seafood consumption, mother's age at delivery and socioeconomic position. Results: Measures of neurocognitive and intellectual function, including full-scale IQ, fine motor coordination, verbal and non-verbal reasoning, learning ability and attention at 11 years old did not show significant variations with prenatal dioxin exposures (proxied by CALUX-TEQ total dioxin load in early breast milk). None of these associations varied by breastfeeding duration or sex. Conclusions: Neurocongitive function, as measured with psychological tests, in 11-year-old children was not associated with prenatal dioxin exposure to background levels of dioxins in the 2000s in Hong Kong.