Mediation effect of air pollution and temperature on the association between greenness and infant’s neurodevelopment: to identify critical windows

Abstract

BACKGROUND AND AIM: Green spaces can have a beneficial effect on health, but little is known about how they affect the neurodevelopment of infants. We investigated to identify mediation effect of TRAPs and temperature mixtures between greenness and infant’s neurodevelopment during windows of susceptibility. METHODS: 418 mother-infant pairs from the mothers and children environmental health (MOCEH) study were analyzed. Daily TRAPs concentrations including PM10 and NO2 were estimated by land-use regression and daily temperature levels obtained from the Korea Meteorological Administration were averaged over each period from pregnancy to 24 months of age. Infant’s neurodevelopment was evaluated based on mental development index (MDI) and physical development index (PDI) at 6 months, 12 months, and 24 months of age assessed by the Korean Bayley Scale of Infant Development II. Bayesian kernel machine regression was used to estimate the mixture index of TRAPs and temperature on infant’s MDI and PDI. Then, causal mediation approach was used to estimate the mediation effect of the mixture index on the association between greenness and infant’s MDI and PDI after adjusting for potential confounders. RESULTS:The total effect of greenness during the entire pregnancy and 6 months from birth on MDI at 6-month-old infants was 1.25 [95% confidence interval: 0.39, 2.39] and 1.09 (0.12, 2.09), respectively. And the indirect effect of the mixture index of TRAPs and temperature during the entire pregnancy and 6 months from birth was each 0.59 (0.19, 1.00) and 0.53(0.04, 1.09). Further, the total effect and the indirect effect of greenness during the entire pregnancy on PDI at 6-month-old infants was 1.45 (0.40, 2.72) and 0.47 (0.12, 0.99). No significant association was observed in other periods. CONCLUSIONS:Our finding suggested that the residential green space has a beneficial effect on infant’s neurodevelopment by reducing overall effect of TRAPs and temperature during pregnancy and early childhood. KEYWORDS: Neurodevelopmental outcomes, Green space, Multi-pollutant, Causal inference