ABSTRACT
This study examines the determinants of susceptibility to the irritant effects of sodium borate in 18 responsive workers identified through repeated self-reports of nasal irritation. For each worker, susceptibility was characterized by two features; reactivity and sensitivity, as estimated from the slope and intercept parameters from their individual exposure-response regression model. Individual estimates of reactivity and sensitivity were then examined to evaluate the importance of personal and environmental characteristics in determining susceptibility. The use of nasal sprays, current smoking and allergies were associated with lower reactivity, while high exposures to borate dust were associated with higher sensitivity. To examine possible biologic mechanisms for the irritant response, a toxicokinetic dose model was used to calculate nasal osmolarity during symptom intervals. The estimated levels suggest that osmolar activation of mast cells to release histamine and other mediators is a plausible mechanism by which these workers may experience nasal irritation.
