Abstract
BACKGROUND: Early life exposure to fine particulate matter (PM(2.5)) is linked to child development, but limited studies have focused on the specific constituents of PM(2.5), and the potential moderating role of residential greenness remains unknown. OBJECTIVES: The aim of this study is to investigate the effects of constituent-specific PM(2.5) on child development and explore the moderating role of greenness. METHODS: This study included 8327 children aged 1-6 years from a nationwide cross-sectional survey in China. We assessed PM(2.5) and its five compositions across six exposure windows, covering the preconception, prenatal, and the year before the developmental assessment. Developmental quotients (DQ) across five domains were examined using the Children's Developmental Scale of China to assess the child development. Greenness was estimated using the Normalized Difference Vegetation Index within a 1000-m buffer (NDVI(1000m)). Multivariable linear regression models were used to evaluate the associations of PM(2.5), its constituents, and child DQ, as well as the effect modification by NDVI(1000m). RESULTS: PM(2.5) and its constituents were negatively associated with child DQ in motor, adaptability, and social skills. These effects varied by DQ domains and constituents, fine and gross motor domains showed more consistent negative associations, and stronger associations were observed for black carbon (BC), organic matter, and sulfates. Especially, PM(2.5) and all five compositions across six windows were consistently associated with lower fine motor DQ [e.g., β = - 4.66, 95% CI: - 5.45, - 3.87, for a 1-ln μg/m(3) increase in PM(2.5) in the year preceding the test]. Additionally, significant interactions were found between PM(2.5), its constituents, and greenness. For example, BC exposure during the year before the test was related to greater decrements in fine motor DQ among children with low NDVI(1000m) (β = - 5.01, 95% CI: - 6.01, - 4.00), compared to those with high NDVI(1000m) (β = - 1.74, 95% CI: - 3.12, - 0.36). CONCLUSIONS: PM(2.5) and its constituents were inversely linked to child development across motor, adaptability, social domains, with greenness potentially serving as a protective factor.