Assessment of Inter-individual Geographic and Seasonal Variability in Estimated Human Exposure to PM_(2.5)

摘要

Scenario-based exposure modeling was used to estimate inter-individual variability, geographic differences, and seasonal differences in the ratios of ambient exposure to ambient concentrations (E_a/C) for PM_(2.5). The model was applied to two example geographic areas that differ with respect housing types and population demographics. Substantial inter-individual variability in E_a/C was estimated for both areas and seasons. The average E_a/C varied from 0.51 to 0.64 depending on the location and season. The results indicate that the average exposure to ambient PM2.5 is substantially less than the ambient concentration. In turn, this implies that concentration-response functions developed in epidemiological studies are biased when compared to exposure concentrations. Regional or seasonal differences in the average E_a/C ratio may confound or help explain variations in concentration-response functions between cities. Furthermore, the E_a/C ratio differs by a factor of approximately 10 among individuals, indicating that some people are very highly exposed compared to others because of factors other than ambient concentration. These findings indicate that exposure, and not just concentration, should be considered in developing risk management strategies.