title: Assessment of inter-individual, geographic, and seasonal variability in estimated human exposure to fine particles.
abstract: Health effects associated with ambient fine particle (PM(2.5)) exposure are typically estimated based on concentration-response (C-R) functions using area-wide concentration as an exposure surrogate. Persons 65 and older are particularly susceptible to adverse effects from PM(2.5) exposure. Using a stochastic microenvironmental simulation model, distributions of daily PM(2.5) exposures were estimated based on ambient concentration, air exchange rate, penetration factor, deposition rate, indoor emission sources, census data, and activity diary data, and compared for selected regions and seasons. Even though the selected subpopulation spends an average of over 20 h per day indoors, the ratio of daily average estimated exposure to ambient concentration (E(a)/C) is approximately 0.5. The daily average E(a)/C ratio varies by a factor of 4-5 over a 95% frequency range among individuals, primarily from variability in air exchange rates. The mean E(a)/C varies by 6-36% among selected NC, TX, and NYC domains, and 15-34% among four seasons, as a result of regional differences in housing stock and seasonal differences in air exchange rates. Variability in E(a)/C is a key factor that may help explain heterogeneity in C-R functions across cities and seasons. Priorities for improving exposure estimates are discussed.
authors.affiliation: Department of Civil, Construction and Environmental Engineering, North Carolina State University, Campus Box 7908, Raleigh, North Carolina 27695-7908, USA.
authors.forename: Wan
authors.initials: W
authors.lastname: Jiao
authors.forename: H Christopher
authors.initials: HC
authors.lastname: Frey
authors.forename: Ye
authors.initials: Y
authors.lastname: Cao
mesh_terms: D000368:Aged; D000393:Air Pollutants / Q000032:analysis*; D002947:Cities; D003198:Computer Simulation; D004784:Environmental Monitoring / Q000379:methods*; D005260:Female; D006801:Humans; D019570:Inhalation Exposure; D008297:Male; D008962:Models, Theoretical; D009519:New York City; D009657:North Carolina; D010316:Particle Size; D052638:Particulate Matter / Q000032:analysis*; D012621:Seasons; D013781:Texas
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter