Ambient air pollution and low birth weight in Connecticut and Massachusetts

Abstract

Background: Several studies have examined whether air pollution affects birth weight; however results vary and many studies were focused on Southern California or were conducted outside of the United States. Objectives: We investigated maternal exposure to particulate matter with aerodynamic diameter < 10, < 2.5 μm (PM10, PM2.5), sulfur dioxide, nitrogen dioxide, and carbon monoxide and birth weight for 358,504 birth in Massachusetts and Connecticut from 1999 to 2002. Methods: Analysis included logistic models for low birth weight (< 2,500 g) and linear models with birth weight as a continuous variable. Exposure was assigned as the average county-level concentration over gestation and each trismester based on mother's residence. We adjusted for gestational lenght, prenatal care, type of delivery, child's sex, birth order, weather, year, and mother's race, education, marital status, age, and tobacco use. Results: An interquartile increase in gestational exposure to NO2, CO, PM10, and PM2.5 lowered birth weigth by 8.9 g (95% confidence interval (CI), 7.0-10.8), 16.2 g (95% CI, 12.6-19.7), 8.2 g (95% CI, 5.3-11.1), and 14.7 g (95% CI, 12.3-17.1) respectively. Lower birth weight was associated with exposure in the third trimester for PM10, the first and third trimester for CO, the first trimester for NO2, and SO2, and the second and third trimester for PM2.5. Effect estimates for PM2.5 were higher for infants of the black mothers than those of white mothers. Conclusions: Results indicate that exposure to air pollution, even at low levels, may increase risk of love birth weight, particularly for some segments of the population.