Dose Estimation for Studies of Acute Respiratory Effects
To modify and expand an existing pharmacokinetic model for nasal dose as well as to develop a new model to estimate tracheobronchial dose of an active agent for each subject in a study of acute respiratory health effects.
|Study Design:||Observational Model: Natural History|
|Study Start Date:||September 1992|
|Estimated Study Completion Date:||August 1995|
Epidemiologic analysis of acute, reversible respiratory health effects is uncommonly performed, yet these are important health outcomes because acute responses by the respiratory defense system appear to represent one end of the continuum toward progressive, chronic and potentially disabling physiologic changes. Repeatable epidemiologic studies of dose-response relationships necessitate accurate measures of 'dose'. However, in occupational and environmental settings, exposure to a toxin is seldom found at identical concentrations and/or particle sizes among persons with the same activity patterns. In addition, air concentration does not account for factors such as clearance or metabolism which may alter the biologically effective tissue dose. These factors cause the target tissue dose of the toxin to vary greatly despite exposure to similar air concentrations.
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.