Exposure Assessment in a Historical Cohort of Filling Station Attendants

Abstract

A historical cohort of service station attendants is underway. It is aimed at evaluating possible excess cancer risk in relation to exposure intensity. In this paper we discuss the feasibility of a retrospective exposure assessment by evaluating the association between indicators of workload and the exposure intensity to some aromatic hydrocarbons measured in a sample of current employees. Available for the analysis were 703 personal samples from 111 filling station workers. Measured concentrations of benzene, toluene and xylenes (8-hour time weighted averages) averaged 0.55 mg/m3, 0.71 mg/m3 and 0.32 mg/m3, respectively. The number of vehicles filled, the daily sales of super premium gasoline and motorbike fuel, and the winter season were all significant predictors of the log concentration of benzene in simple regression analyses. The size of the station acted as an effect modifier. While no single variable was able to predict the benzene level in large stations, for small stations an increase of 0.0579 and of 0.0418 in the log benzene concentration per unit increase in super premium gasoline (100 I) and in motorbike fuel (10 I) dispensed, was estimated. The overall variance explained by the multivariate model, however, was only 12.3%. Therefore, a clear categorization of groups with homogeneous and significantly different exposure levels is not achievable. From the point of view of exposure assessment, workers in small stations with higher sales of super premium gasoline tend to have higher exposure levels. This group should be examined in detail when the final results of the cohort study are available.