The causal impact of fetal exposure to PM2.5 on birth outcomes: Evidence from rural China

This paper investigates the causal impact of fetal exposure to PM2.5 on birth outcomes, including birth weight, the incidence of low birth weight (LBW), and small for gestational age (SGA), based on a nationally representative birth record dataset in a developing country setting. We employed thermal inversion as the instrument variable (IV) for PM2.5 and leveraged the distinctive characteristics of rural China in the 1990 s to address identification challenges. Our IV estimates indicate that higher fetal PM2.5 exposure leads to lower birth weight and elevated probabilities of LBW and SGA. Due to the mortality selection in utero, weak male fetuses were more likely to be screened out by PM2.5 exposure, resulting in a comparatively lower vulnerability among the surviving male infants. Furthermore, infants born to less educated mothers exhibited increased susceptibility, a phenomenon not entirely explained by the sorting behaviors associated with the preference for cleaner air based on socioeconomic status.