Subjective Estimation of Toluene Exposures: A Calibration Study of Industrial Hygienists

Abstract

The ability of a group of industrial hygienists to predict exposures based on experience and professional judgment was evaluated. Eight-hour time-weighted average toluene exposures for a group of batch chemical process workers were measured over a three-week period. These 134 personal measurements comprised the empirical distribution of exposures. Twenty-four industrial hygienists with expertise in assessing exposures in batch chemical processing operations were randomly selected for the study after a formal nomination process. Each industrial hygienist participated in a three-hour personal interview which followed a standard protocol. During the interview, each expert reviewed chemical process information and then subjectively assessed the distribution of exposures and the average exposure among the workers. After limited historical exposure data were presented, elicitations of the subjective distribution and the average exposure were repeated. Industrial hygienists estimated the average exposure and the 90th percentile of the exposure distribution with a remarkable degree of accuracy, especially after reviewing the limited exposure data. Results for the lower percentiles of the distribution were less accurate. Results suggest that experienced hygienists may be competent at providing subjective estimates of average exposures for retrospective epidemiological studies and prospective hazard evaluation.