Ambient Fine Particulate Matter, Nitrogen Dioxide, and Term Birth Weight in New York City

Abstract

Background The growing volume of studies addressing the association between air pollution and pregnancy outcomes remains inconclusive due to methodologic limitations. Using a unique community air pollution survey in New York City, we addressed this question with improved exposure assessment, a large number of births, freedom from confounding by socioeconomic status, and refined analytic methods. Aims We assessed the relationship between exposure to ambient pollutants, fine particulate matter (PM2.5) and nitrogen dioxide (NO2), and a term birth weight, considering trimester-specific and aggregate pregnancy exposure. Methods We included 252,967 singleton, term births to non-smokers, without congenital malformations, with known address, with birth dates in the years 2008-2010 restricted to avoid fixed cohort bias. Data from the New York City Community Air Survey were used to estimate exposure for all two week periods at all residences based on a network of 150 monitors. We examined term birth weight (37-42 weeks’ gestation), adjusting for maternal age, ethnicity, education, parity, insurance status, neighborhood socioeconomic indices, week of gestation, and calendar year using linear mixed models. Results An interquartile shift in PM2.5 in the three trimesters and over the entire pregnancy was associated with predicted birthweight decrements of 6.1, 3.3, 8.5, and 11.9 grams, respectively. For NO2, an interquartile shift in exposure for the three trimesters and total pregnancy predicted greater birthweight decrements of 11.3, 12.6, 13.6, and 11.2 grams, respectively. Conclusions Intra-urban and temporal sources of variation in PM2.5 and NO2 show a clear statistical association with a reduction in birth weight, adding to evidence from other studies that exposure to combustion pollutants may adversely affect fetal growth. The estimated effect, while modest at the individual level, would have important implications for population health if causal.