The estimation of personal exposures to air pollutants for a community-based study of health effects in asthmatics--exposure model.

Abstract

Estimates of individual personal exposure to ozone, nitrogen dioxide, pollen, temperature, and relative humidity for a group of asthmatics participating in a health effects study were obtained by means of a modelling approach utilizing fixed site monitoring data, regression relationships between fixed site and indoor and outdoor microenvironment concentrations, study subject activity patterns and study household characteristics. A considerable improvement in the accuracy of exposure assessment using the exposure model instead of fixed site measurements alone was demonstrated for ozone. This large refinement of zone exposure estimates was achieved using a simplified approach which emphasized the large differences between indoor and outdoor microenvironmental concentrations, and assumed relatively little heterogeneity in exposure within either of these two broad microenvironmental categories. Major sources of error in the exposure model for ozone include: failure to include indoor microenvironments with no air conditioning in the development of the model, inability to accurately apportion within-hour time spent in different microenvironments, and misclassification of hour-specific personal location by study subjects.