Fine particulate air pollution and birthweight: Differences in associations along the birthweight distribution.

Fong KC, Kosheleva A, Kloog I, Koutrakis P, Laden F, Coull BA, Schwartz JD. (2019). Fine particulate air pollution and birthweight: Differences in associations along the birthweight distribution. Epidemiology.

Studies have documented the effects of prenatal fetal exposure to fine particulate matter (PM2.5) on birthweight, often linking PM2.5 exposure to lower newborn birthweight. Many of these studies investigate the association between PM2.5 exposure and birthweight using generalized additive models and simple linear regressions, which do provide an overall association but say nothing about how exposure to PM2.5 is associated with differences across a birthweight distribution. Harvard doctoral student, Kelvin Fong, with the guidance of Dr. Laden (CRESSH Co-Director) published a study in September to understand the association between PM2.5 exposure in utero and newborn’s birthweight along the birthweight distribution by using quantile regression. The research team collected 775,768 individual birth data from the Massachusetts Birth Registry, and split the group up into 10 equal parts (deciles) by birthweight to create a quantile. Mother’s addresses were geocoded, and PM2.5 estimates were collected using hybrid models that use both land regression and satellite remote sensing data to provide temporal and spatial PM2.5 exposure estimates on a1 x 1 km grid. After adjusting for covariates, the authors measured the association between PM2.5 and birthweight using linear regression analysis and quantile regression analysis. From the linear regression, the team found that higher exposure to PM2.5 was associated with lower birthweight, in that, on average, an interquartile range increase in PM2.5 exposure was associated with a 16g lower birthweight among newborns. The authors also found that in utero exposure to PM2.5 had more negative impacts on the newborn population’s birthweight at lower birthweight deciles, implying that PM2.5 exposure may have a larger impact among lighter newborns than heavier newborns. The authors recommend that their findings could help inspire future research to study the physiological mechanisms linking exposure to air pollution to birthweight outcomes.

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