Relation between ambient air pollution and low birth weight in the northeastern United States

We evaluated the relation between term low birth weight (LBW) and ambient a ir levels of carbon monoxide (CO), particulate matter up to 10 mum in diame ter (PM10), and sulfur dioxide (SO2). The study population consisted of sin gleton, term live births (37-44 weeks of gestation) born between 1 January 1994 and 31 December 1996 in six northeastern cities of the United States: Boston, Massachusetts; Hartford, Connecticut; Philadelphia, Pennsylvania; P ittsburgh, Pennsylvania; Springfield, Massachusetts; and Washington, DC. Bi rth data were obtained from National Center for Health Statistics Natality Data Sets. Infants with a birth weight < 2,500 g were classified as LBW. Ai r monitoring data obtained from the U.S. Environmental Protection Agency we re used to estimate average trimester exposures to ambient CO, PM10, and SO 2. Our results suggest that exposures to ambient CO and SO2 increase the ri sk for term LBW. This risk increased by a unit increase in CO third trimest er average concentration [adjusted odds ratio (AOR) 1.31; 95% confidence in terval (CI) 1.06,1.62]. Infants with SO2 second trimester exposures falling within the 25 and < 50th (AOR 1.21; CI 1.07,1.37), the 50 to < 75th (AOR 1 .20; CI 1.08,1.35), and the 75 to < 95th (AOR 1.21; CI 1.03,1.43) percentil es were also at increased risk for term LBW when compared to those in the r eference category (< 25th percentile). There was no indication of a positiv e association between prenatal exposures to PM10 and term LBW. Increased am bient levels of air pollution may be associated with an increased risk for LBW.