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Population exposure to ultrafine particles: size-resolved and real-time models for highways
Zhu, Shanjiang, Julian Marshall and David Levinson (2016) Population exposure to ultrafine particles: size-resolved and real-time models for highways. Transportation Research part D: Transport and Environment. (online first) [doi] [free until January 6, 2017]
• This study estimates individual and population exposure to ultra-fine particles in the Minneapolis – St. Paul (Twin Cities) metropolitan area, Minnesota.• We combine a model of on-highway size-resolved UFP concentrations with GPS travel patterns.• The most significant exposures were found at freeway interchanges.• Peak hour concentration is about 10 times larger than the off-peak hour concentration.• Peak hour exposure is about 100 times compared to its off-peak hour counterpart.
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, 5.5–600 nm); individual travel patterns, derived from GPS travel trajectories collected in 144 individual vehicles (123 h 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.