Document Type

Working Paper

Date of this Version



This paper is part of the project "Prenatal Air Pollution Exposures and Early Childhood Outcomes," which is supported by a grant from the Penn China Research and Engagement Fund (PIs: Behrman and Hannum) and by National Science Foundation Grant 1756738 (PI: Hannum). The authors also gratefully acknowledge support from the University of Houston Research Fund and, for coverage of Wang’s time, Scholar Grant GS040-A-18 from the Chiang Ching-Kuo Foundation.


This paper investigates whether associations between birth weight and prenatal ambient environmental conditions—pollution and extreme temperatures—differ by 1) maternal education; 2) children’s innate health; and 3) interactions between these two. We link birth records from Guangzhou, China, during a period of high pollution, to ambient air pollution (PM10 and a composite measure) and extreme temperature data. We first use mean regressions to test whether, overall, maternal education is an “effect modifier” in the relationships between ambient air pollution, extreme temperature, and birth weight. We then use conditional quantile regressions to test for effect heterogeneity according to the unobserved innate vulnerability of babies after conditioning on other confounders. Results show that 1) the negative association between ambient exposures and birth weight is twice as large at lower conditional quantiles of birth weights as at the median; 2) the protection associated with college-educated mothers with respect to pollution and extreme heat is heterogeneous and potentially substantial: between 0.02 and 0.34 standard deviations of birth weights, depending on the conditional quantiles; 3) this protection is amplified under more extreme ambient conditions and for infants with greater unobserved innate vulnerabilities.


This working paper was published in a journal:

Liu, Xiaoying, Jere Behrman, Emily Hannum, Fan Wang, and Qingguo Zhao. 2021. "Same Environment, Stratified Impacts? Air Pollution, Extreme Temperatures, and Birth Weight in South China." Social Science Research:102691.


air pollution, birth weight, maternal education, extreme temperatures, China



Date Posted: 06 January 2021