Air pollution and newborns revisited: granular evidence from South Korea

Abstract This study examines the impact of in utero exposure to ambient particulate matter (PM) on neonatal health outcomes, utilizing comprehensive population-level birth records from South Korea for pregnancies between 2016 and 2019. To address potential endogeneity concerns, the analysis adopts wind direction as an instrumental variable for prenatal PM exposure. The findings indicate that exposure to PM during the first trimester significantly increases the likelihood of preterm birth, and this effect remains robust across a range of model specifications. Because PM2.5 and PM10 co-move, we interpret the estimates as effects of broader particulate pollution rather than PM2.5 alone. Moreover, the estimated impacts are consistent across different socioeconomic strata. These results highlight the critical importance of environmental health during early pregnancy and suggest that in low-fertility, late-childbearing societies such as South Korea, environmental protection efforts should be closely aligned with maternal health policies.