Ambient air pollution and pregnancy outcomes—a study of functional form and policy implications
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We utilize a new data set on ambient air pollution and births from the Salt Lake Valley to study how intensive and cumulative exposure to PM2.5 in the first trimester affect two important pregnancy outcomes—gestational age at birth and the risk of preterm birth. For identification, we use variation in cumulative exposure for siblings from the same mother in subsequent pregnancies, which can be substantial due to the large seasonal and annual variations in the valley. Controlling for other air pollutants and individual confounders, we find strong evidence of reduced gestational age and increased probability of preterm birth resulting from PM2.5 exposure and estimate that the marginal effects are larger as cumulative exposure increases. We find weak evidence of an increased marginal effect of intensive exposure vs. total exposure. As cumulative exposure plays a larger role than intensive exposure, this indicates that policies which decrease average pollution levels can be more effective than policies targeted at peak pollution from a pregnancy perspective.
KeywordsPM2.5 Preterm birth Environmental policy Prenatal exposure
We would like to thank Gabriel Lozada, Sara Simonsen, and Norman Waitzman for their insightful comments and support. This project was possible thanks to the data support received from Mylitta Barrett at the Salt Lake City Health Department and Kenneth Symons at the Utah Department of Air Quality. We thank Jessica Sanders, Adrienne Cachelin, Chris Pounds, and Susanna Cohen for their conceptual and contextual contributions. This study was approved by the University of Utah IRB, number 00070638. This paper has emerged from Hackmann’s master thesis Associations between the Wasatch Front air pollution (winter inversion) during the first trimester of pregnancy, preterm birth, and the economic costs to the health care system.
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