Population exposure to ultrafine particles: size-resolved and real-time models for highways

Abstract

Prior research on ultrafine particles (UFP) emphasizes that concentrations are especially high on-highway, and that time on highways contribute disproportionately to total daily exposures. This study estimates individual and population exposure to ultra-fine particles in the Minneapolis – St. Paul (Twin Cities) metropolitan area, Minnesota. Our approach combines a real-time model of on-highway size-resolved UFP concentrations (32 bins, 5.5 to 600 nm); individual travel patterns, derived from GPS travel trajectories collected in 144 individual vehicles (123 hours at locations with UFP estimates among 624 vehicle-hours of travel); and, loop-detector data, indicating real- time traffic conditions throughout the study area. The results provide size-resolved spatial and temporal patterns of exposure to UFP among freeway users. On-highway exposures demonstrate significant variability among users, with highest concentrations during commuting peaks and near highway interchanges. Findings from this paper could inform future epidemiological studies in on- road exposure to UFP by linking personal exposures to traffic conditions.