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Workplace air samples analyzed for benzene at four US refineries from 1976 to 2007 were pooled into a single dataset to characterize similarities and differences between job titles, tasks and refineries, and to provide a robust dataset for exposure reconstruction. Approximately 12,000 non-task (>180 min) personal samples associated with 50 job titles and 4000 task (<180 min) samples characterizing 24 tasks were evaluated. Personal air sample data from four individual refineries were pooled based on a number of factors including (1) the consistent sampling approach used by refinery industrial hygienists over time, (2) the use of similar exposure controls, (3) the comparability of benzene content of process streams and end products, (4) the ability to assign uniform job titles and task codes across all four refineries, and (5) our analysis of variance (ANOVA) of the distribution of benzene air concentrations for select jobs/tasks across all four refineries. The jobs and tasks most frequently sampled included those with highest potential contact with refinery product streams containing benzene, which reflected the targeted sampling approach utilized by the facility industrial hygienists. Task and non-task data were analyzed to identify and account for significant differences within job-area, task-job, and task-area categories. This analysis demonstrated that in general, areas with benzene containing process streams were associated with greater benzene air concentrations compared to areas with process streams containing little to no benzene. For several job titles and tasks analyzed, there was a statistically significant decrease in benzene air concentration after 1990. This study provides a job and task-focused analysis of occupational exposure to benzene during refinery operations, and it should be useful for reconstructing refinery workers' exposures to benzene over the past 30 years.

While petroleum industry studies have indicated low benzene exposure potential for refinery workers, most provide limited data for assessing job or task-related benzene exposures. This study characterizes job and task-specific airborne benzene concentrations and variability over time for the ExxonMobil refinery in Joliet, Illinois from 1977 to 2006. A database of 2289 industrial hygiene air samples, including 1145 non-task (≥180 min) personal samples and 480 task-related (<180 min) personal samples, were analyzed. Samples were grouped by operational status, job, and task. Benzene concentrations were determined for each job category and task bin, with additional analyses conducted to determine whether benzene concentrations changed over time. The results indicate that the benzene concentrations for non-task and task samples were relatively low. For all non-task samples, the arithmetic mean benzene concentration was 0.12 part per million (ppm). The most frequently sampled workers (process technicians during routine operations) had an arithmetic mean benzene concentration of 0.038 ppm. The most frequently sampled task bin (blinding and breaking) had an arithmetic mean benzene concentration of 1.0 ppm. This study provides benzene air concentration data that can be used in combination with job histories to reconstruct historical benzene exposures for workers at the Joliet Refinery over the past 30 years.