Effects of prenatal exposures to air sulfur dioxide/nitrogen dioxide on toddler neurodevelopment and effect modification by ambient temperature

Emerging evidence suggests that prenatal exposure to ambient SO₂ or NO₂ induces fetal brain-damage. However, effects of prenatal exposure to SO₂ or NO₂ on toddler neurodevelopment and the effect-modification by ambient temperature remain unclear. Therefore, a prospective birth-cohort study was conducted from 2010 to 2012 in Shanghai, and 225 mother-child pairs were followed-up from mid-to-late pregnancy until 24-36 months postpartum. During the whole pregnancy, daily SO₂/NO₂ and temperature levels were obtained for each woman. Gesell-Development-Schedule was used to assess toddler neurodevelopment in the domains of gross-motor, fine-motor, adaptive-behavior, language and social-behavior. Distributed-lag-nonlinear-models simultaneously accounting for exposure-response and lag-response associations were applied to assess the impacts of prenatal SO₂/NO₂ exposure on neurodevelopment. Each 10-μg/m³ increase in weekly average SO₂ concentrations had adverse associations with gross-motor in gestational-weeks 1-6, with adaptive-behavior in weeks 26-30, and with language in weeks 30-36 (developmental-quotient changes: - 1.17% to - 0.12%, P-values < 0.05). Each 10-μg/m³ increase in weekly average NO₂ concentrations had adverse associations with gross-motor in gestational-weeks 33-36, with fine-motor in weeks 26-36 and with social-behavior in weeks 31-36 (developmental-quotient changes: - 0.91% to - 0.20%, P-values < 0.05). The cumulative effects for the whole pregnancy showed that each 10-μg/m³ increase in SO₂ induced significant deficits in gross-motor and adaptive-behavior (developmental-quotient changes: - 4.71% and - 4.06%, respectively, P < 0.05). We found prenatal cumulative SO₂ exposure induced more deficits in low temperature in language and adaptive-behavior than in high/moderate temperature. Thus, prenatal ambient SO₂/NO₂ exposure in specific time-windows (1st and 3rd trimesters for SO₂; 3rd trimester for NO₂) could impair toddler neurodevelopment and low temperature may aggravate the SO₂-induced neurotoxicity.