title: The Association between Airborne PM2.5Chemical Constituents and Birth Weight-Implication of Buffer Exposure Assignment.
abstract: Several papers reported associations between airborne fine particulate matter (PM2.5) and birth weight, though findings are inconsistent across studies. Conflicting results might be due to (1) different PM2.5chemical structure across locations, and (2) various exposure assignment methods across studies even among the studies that use ambient monitors to assess exposure. We investigated associations between birth weight and PM2.5chemical constituents, considering issues arising from choice of buffer size (i.e. distance between residence and pollution monitor). We estimated the association between each pollutant and term birth weight applying buffers of 5 to 30km in Connecticut (2000-2006), in the New England region of the U.S. We also investigated the implication of the choice of buffer size in relation to population characteristics, such as socioeconomic status. Results indicate that some PM2.5chemical constituents, such as nitrate, are associated with lower birth weight and appear more harmful than other constituents. However, associations vary with buffer size and the implications of different buffer sizes may differ by pollutant. A homogeneous pollutant level within a certain distance is a common assumption in many environmental epidemiology studies, but the validity of this assumption may vary by pollutant. Furthermore, we found that areas close to monitors reflect more minority and lower socio-economic populations, which implies that different exposure approaches may result in different types of study populations. Our findings demonstrate that choosing an exposure method involves key tradeoffs of the impacts of exposure misclassification, sample size, and population characteristics.
authors.affiliation: School of Forestry and Environmental Studies, Yale University, 195 Prospect Street, New Haven, CT 06511 USA.
authors.forename: Keita
authors.initials: K
authors.lastname: Ebisu
authors.affiliation: School of Public Health, Yale University, 60 College Street, New Haven, CT 06520 USA.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Belanger
authors.affiliation: School of Forestry and Environmental Studies, Yale University, 195 Prospect Street, New Haven, CT 06511 USA.
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Bell
keywords: Air Pollution; Environmental Epidemiology; Environmental Health; Low Birth Weight; PM2.5