Project title: Measurement and Analysis of Benzene and Hydrogen Sulfide Exposures for Workers at an Oil Refinery
Completed in: 2015 | Faculty advisor: Noah S. Seixas
Petroleum refining is an industry that poses many health risks to workers, including exposure to the gases benzene and hydrogen sulfide (H2S). Although several studies have been conducted with the attempt to characterize exposures of magnitude depending on various environmental factors, it is important to focus on site-specific exposures due to the wide variation in plant design and work practices. The goal of this study was to expand the knowledge of areas where H2S and benzene exposures would likely be highest for defined workers, as well as to increase the potential for future efforts with enhanced economic focus. This study looked at the variability in benzene and H2S exposure based on job task (laboratory workers, sample station operators, comparison gauging personnel), as well as by examining the exposures based on the processing stage of the fuel components being measured (early, mid, late) for a refinery. Realtime (PID and multi-gas monitors in ppm) and full-shift (organic vapor monitors, sPMA urine samples, passive H2S tubes) monitoring was performed in attempt to characterize the exposure trends. Based on the monitoring data, benzene exposures appeared to depend on job task with comp. gauging personnel the most likely for highest exposure (n=251) [F(2,248) = 15.60, p<0.001], but the processing stage of the fuel components was not a significant predictor of exposure at the tanks [F(2, 28) = 2.87, p=0.07]. H2S exposure trends were the opposite of those observed from benzene. The highest exposures were from the times the personnel were working with fuel components in the earlier processing stages [F(2,44) = 4.58, p=0.02], and the job task exposures did not exhibit major differences when comparing the mean air concentrations of them [F(2,61) = 0.84, p=0.44]. None of the full-shift monitors produced results above their limits of detection. Since H2S appeared to have been reduced as the fuel components moved through the processes, it may be beneficial to focus on the “upstream” areas of the refinery to ensure lowest achievable exposures are reached. The comp. gauging personnel should be given separate training and knowledge of the tanks where benzene exposures would be highest and use respirators as required.