title: Variability in the fraction of ambient fine particulate matter found indoors and observed heterogeneity in health effect estimates.
abstract: Exposure to ambient (outdoor-generated) fine particulate matter (PM(2.5)) occurs predominantly indoors. The variable efficiency with which ambient PM(2.5) penetrates and persists indoors is a source of exposure error in air pollution epidemiology and could contribute to observed temporal and spatial heterogeneity in health effect estimates. We used a mass balance approach to model F for several scenarios across which heterogeneity in effect estimates has been observed: with geographic location of residence, residential roadway proximity, socioeconomic status, and central air-conditioning use. We found F is higher in close proximity to primary combustion sources (e.g. proximity to traffic) and for lower income homes. F is lower when PM(2.5) is enriched in nitrate and with central air-conditioning use. As a result, exposure error resulting from variability in F will be greatest when these factors have high temporal and/or spatial variability. The circumstances for which F is lower in our calculations correspond to circumstances for which lower effect estimates have been observed in epidemiological studies and higher F values correspond to higher effect estimates. Our results suggest that variability in exposure misclassification resulting from variability in F is a possible contributor to heterogeneity in PM-mediated health effect estimates.
authors.affiliation: Department of Environmental Sciences, Rutgers University, New Brunswick, New Jersey 08901, USA.
authors.forename: Natasha
authors.initials: N
authors.lastname: Hodas
authors.forename: Qingyu
authors.initials: Q
authors.lastname: Meng
authors.forename: Melissa M
authors.initials: MM
authors.lastname: Lunden
authors.forename: David Q
authors.initials: DQ
authors.lastname: Rich
authors.forename: Halûk
authors.initials: H
authors.lastname: Ozkaynak
authors.forename: Lisa K
authors.initials: LK
authors.lastname: Baxter
authors.forename: Qi
authors.initials: Q
authors.lastname: Zhang
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: Turpin
mesh_terms: D000389:Air Conditioning; D016902:Air Pollution, Indoor / Q000009:adverse effects / Q000706:statistics & numerical data*; D004781:Environmental Exposure / Q000009:adverse effects / Q000706:statistics & numerical data; D006801:Humans; D008962:Models, Theoretical; D052638:Particulate Matter / Q000009:adverse effects / Q000032:analysis*; D012111:Residence Characteristics; D012959:Socioeconomic Factors
chemical_list: D052638:Particulate Matter