The results of these toxicokinetic models were individual measures of tissue dose used in a 2-stage epidemiologic analysis which placed special emphasis on the definition of individual dose-response curves for exposure to an irritant dust, sodium borate, and the reversible effects of peak expiratory flow and irritant symptoms. A primary advantage of the two stage epidemiologic approach was that it permitted particular attention to be focused on the factors which determined the sensitivity (threshold) and reactivity (slope) for an individual. The use of tissue dose estimates were also compared to simple exposure measurements in the epidemiologic analysis to evaluate the efficacy of using dosimetric methods in epidemiologic studies.