Factors Affecting the Association between Ambient Concentrations and Personal Exposures to Particles and Gases

摘要

Results from air pollution exposure assessment studies suggest that ambient fine particles [paniculate matter with aerodynamic diameter <= 2.5 mu g(PM_(2.5))],but not ambient gases,are strong proxies of corresponding personal exposures.For particles,the strength of the personal-ambient association can differ by particle component and level of home ventilation.For gases,however,such as ozone(O_3),nitrogen dioxide(NO_2),and sulfur dioxide(SO_2),the impact of home ventilation on personal-ambient associations is untested.We measured 24-hr personal exposures and corresponding ambient concentrations to PM_(2.5),sulfate(SO_4~(2-)),elemental carbon,O_3,NO_2,and SO_2 for 10 nonsmoking older adults in Steubenville,Ohio.We found strong associations between ambient particle concentrations and corresponding personal exposures.In contrast,although significant,most associations between ambient gases and their corresponding exposures had low slopes and R~2 values;the personal-ambient NO,association in the tall season was moderate.For both particles and gases,personal-ambient associations were highest for individuals spending most of their time in high-compared with low-ventilated environments.Cross-pollutant models indicated that ambient particle concentrations were much better surrogates for exposure to particles dun to gases.With the exception of ambient NO_2 in the fall,which showed moderate associations with personal exposures,ambient gases were poor proxies for both gas and particle exposures.In combination,our results suggest that a)ventilation may be an important modifier of the magnitude of effect in time-series health studies,and b)results from time-series health studies based on 24-hr ambient concentrations are more readily interpretable for particles than for gases.