The effect of ambient air pollution on birth outcomes in Norway

Ambient air pollution is harmful to the fetus even in countries with relatively low levels of pollution. In this paper, I examine the effects of ambient air pollution on birth outcomes in Norway. I find that prenatal exposure to ambient nitric oxide in the last trimester causes significant birth weight and birth length loss under the same sub-postcode fixed effects and calendar month fixed effects, whereas other ambient air pollutants such as nitrogen dioxide and sulfur dioxide appear to be at safe levels for the fetus in Norway. In addition, the marginal adverse effect of ambient nitric oxide is larger for newborns with disadvantaged parents. Both average concentrations of nitric oxide and occasional high concentration events can adversely affect birth outcomes. The contributions of my work include: first, my finding that prenatal exposure to environmental nitric oxide has an adverse effect on birth outcomes fills a long-standing knowledge gap. Second, with the large sample size and geographic division of sub-postal codes in Norway, I can control for a rich set of spatio-temporal fixed effects to overcome most of the endogeneity problems caused by the choice of residential area and date of delivery. In addition, I study ambient air pollution in a low-pollution setting, which provides new evidence on the health effects of low ambient air pollution.