Validation of personal exposure models for sulfate and aerosol strong acidity.

Personal exposure models for sulfates (SO4 =) and aerosol strong acidity (H+) were previously developed using concentration and activity pattern data collected from a personal monitoring study conducted in Uniontown, Pennsylvania, during the summer of 1990. Models were constructed based on time-weighted micro-environmental exposures. For SO4 =, the "best-fit" model included a correction factor, while for H+, it included both a correction factor and a neutralization term. In this paper, we present the validation of these models using data collected in a personal monitoring study conducted in State College, Pennsylvania, during the summer of 1991. Indoor and outdoor concentration and activity pattern data collected in this study were used as inputs for the "best-fit" models for SO4 = and H+. Predicted personal exposures subsequently were compared to the measured personal exposures from State College to determine their accuracy and precision. Predicted personal exposures for both SO4 = and H+ were in excellent agreement with measured personal exposures from State College. The models explained 91 and 62 percent of the variability in personal SO4 = and H+ exposures, respectively, and were able to estimate personal exposures substantially better than outdoor concentrations alone. Validation results suggest that the models' correction and neutralization factors are not site specific and support the models' future application as a technique to assess the personal acid aerosol exposures of children living in similar rural and semi-rural communities.