STI scientists developed the Regional Human Exposure Model (REHEX) to estimate population exposure to and dosage from air pollutants. The REHEX model uses an approach that accounts for the amount of time people spend in various microenvironments and for their levels of physical activity. It employs an indoor air quality mass-balance model to estimate indoor concentrations as a function of the source strengths, air exchange rates, building volumes, and deposition rates. The REHEX model has been applied to examine population exposure to ozone, nitrogen dioxide, PM10, benzene, and other airborne toxic compounds. STI scientists have applied the REHEX model to estimate general population exposures in Los Angeles, San Francisco, and Houston. We developed a version of the model for use in cohort studies where subject-specific housing, school, and time-activity data are available.
This model has been applied using Monte Carlo simulations of children's exposure in Southern California (for the Children's Health Study sponsored by the California Air Resources Board).