Prenatal exposure to PM2.5 and infant health: Evidence from Quebec

We examine the effects of prenatal exposure to fine particulate matter (PM_2.5) on birth outcomes in a low-pollution setting. We combine administrative birth records in Quebec between 2008 and 2015 with air quality monitoring data and linked tax records in h neighborhood-by-quarter fixed effects models. While we find little evidence that prenatal PM_2.5 exposure substantially affects birth outcomes on average at the population level, we unmask important heterogeneity. Constructing a cumulative socioeconomic vulnerability index, we find that in most vulnerable families a 1μg/m³ increase in average PM_2.5 exposure is associated with a reduction of approximately 6.6 grams in birth weight. Focusing on a sample of births admitted to one of the province's neonatal care unit, we also find important effects of in utero PM_2.5 exposure on biologically vulnerable newborns, both in terms of prematurity and of birth weight. We also find that days exceeding the Canadian 24-hour PM_2.5 standard have disproportionately large effects among vulnerable families, such that peaks in exposure matter beyond average exposure itself.