Early Life Exposure to Ambient Air Pollutants is Associated with Decreased Cognitive Development in Hispanic Infants from Southern California

BACKGROUND AND AIM: Previous research has established an association between postnatal ambient air pollution (AAP) exposure and cognitive development in preschoolers and school-aged children. However, this association has not been examined during infancy, a critical neurodevelopmental window. The purpose of this study was to explore relationships between postnatal AAP exposure and cognitive development in infants. METHODS: This study examined 118 Hispanic mother-infant pairs from the longitudinal Mother’s Milk Study in Southern California. Average individual residential exposure to AAP, including nitrogen dioxide (NO2) and particulate matter smaller than 2.5 and 10 microns in diameter (PM2.5 and PM10 respectively), in the first month of life was estimated from central site monitors. Infant cognitive outcomes at 24-months were measured using the Bailey-III Scales of Infant and Toddler Development. Multivariate linear regression was used to examine relationships between postnatal AAP exposure and age scaled cognitive scores, adjusting for socioeconomic status, breastfeeding frequency, time of delivery (early/late/on-time) as a proxy for gestational age, pre-pregnancy BMI, birthweight, and sex. Effects are reported for each standard deviation increase in exposure. RESULTS:NO2 was negatively associated with fine motor score (β=-0.55, p=0.006), motor score (β=-0.90, p =0.007), and cognitive score (β=-0.55, p=0.01). PM2.5 and PM10 were negatively associated with social emotional scores (β=-0.77, p=0.009 and β=-0.66, p=0.01 respectively). The association between NO2 and cognitive score varied by infant sex (p-interaction = 0.046), where NO2 was negatively associated with cognitive score among females (β=-0.16, p=0.0006) but not males (β=-0.01, p=0.81). CONCLUSIONS:Higher postnatal exposure to AAP in the first month of life was inversely associated with scaled motor, cognitive, and social-emotional scores at 24-months of age. Sex-specific findings for scaled cognitive score may suggest differential impacts of AAP exposure among females. These results indicate that AAP may negatively impact neurodevelopment in early life. KEYWORDS: Air Pollution, Neurodevelopmental Outcomes, Multi-pollutant, Environmental Disparities, Short-term Exposure