Ambient Air Pollution and Birth Weight in Full-Term Infants in Atlanta, 1994-2004

Abstract

ISEE-0430 Background and Objective: An emerging body of evidence suggests ambient levels of air pollution during pregnancy are associated with fetal growth. Methods: We used vital records data to construct a retrospective cohort of 406,627 full-term births occurring between 1994 and 2004 in five central counties of metropolitan Atlanta, USA. We examined the relationship between birth weight and temporal variation in ambient levels of carbon monoxide (CO), nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), PM10 (particulate matter <10 μm in diameter), PM2.5 (particulate matter <2.5 μm in diameter) and speciated PM2.5 measurements. Daily pollutant levels in five-county Atlanta were characterized using a population-weighted spatial average of air quality monitors in the study area. Daily concentrations were then averaged over the time period corresponding to each infant's third trimester. We also conducted capture-area analyses limited to mothers residing within four miles (6.4 km) of each air quality monitoring station. Linear regression models included control for seasonal and long-term time trends, gestational week, maternal education, maternal marital status, maternal age, maternal tobacco use, race and ethnicity, and parity. Results: In the five-county analysis, ambient levels of NO2, SO2, PM2.5 elemental carbon and PM2.5 water-soluble metals were significantly associated with small reductions in birth weight in full-term infants (−4 to −16 grams per interquartile range [IQR] increase in pollutant concentrations). The capture-area analyses provided little evidence of harmful effects of air pollution, but confidence intervals were wide. Conclusion: Results provide limited support for an effect of ambient air pollution in the third trimester on birth weight in full-term infants.