Occupational Exposure to Benzene at the ExxonMobil Refinery at Baton Rouge, Louisiana (1977–2005)

Abstract

Because crude oil contains up to 3% benzene and there is an association between high chronic exposure to appreciable concentrations of benzene and acute myelogenous leukemia, exposure of refinery workers has been studied for many years. To date, no extensive industrial hygiene exposure analyses for historical benzene exposure have been performed, and none have focused on the airborne concentrations in the workplace at specific refineries or for specific tasks. In this study, the authors evaluated the airborne concentrations of benzene and their variability over time at the ExxonMobil refinery in Baton Rouge between 1977 and 2005. Refinery workers were categorized into 117 worker groups using company job descriptions. These 117 groups were further collapsed into 25 job categories based on similarity of measured exposure results. Results of 5289 personal air samples are included in this analysis; 3403 were considered nontask (≥ 180 min) personal samples, and 830 were considered task-related (< 180 min) personal samples; the remainder did not fit in either category. In general, nontask personal air samples indicated that exposures of the past 30 years were generally below the occupational exposure limit of 1 ppm, but there was only a small, decreasing temporal trend in the concentrations. The job sampled most frequently during routine operations was process technician and, as broken down by area, resulted in the following mean benzene concentrations: analyzers (mean = 0.12 ppm), coker (mean = 0.013 ppm), hydrofiner (mean = 0.0054 ppm), lube blending and storage (mean = 0.010 ppm), waste treatment (mean = 0.092 ppm), and all other areas (mean = 0.055 ppm). Task-based samples indicated that the highest exposures resulted from the sampling tasks, specifically from those performed on process materials; in general, though, even these tasks had concentrations well below the STEL of 5 ppm. The most frequently sampled task was gauging (mean = 0.12 ppm). Task-related exposures were also similar across job categories for a given task, with a few exceptions. This study thus provides a task-focused analysis for occupational exposure to benzene during refinery operations, which can be insightful for understanding exposures at this refinery and perhaps others operated since about 1975.

Keywords:

• benzene
• exposure assessment
• industrial hygiene
• refineries

ACKNOWLEDGMENTS

The authors thank Paul Scott of ChemRisk for his assistance with the statistical analysis, and Annabelle Javier for her assistance in assembling and organizing the electronic data. This work was funded by ExxonMobil, a company that has been involved in the study of benzene for several decades and is involved in litigation involving benzene. At least two of the authors have served or are likely to serve as expert witnesses for ExxonMobil on matters relating to industrial hygiene, exposure assessment, risk assessment, or toxicological issues related to benzene.

[Supplemental materials are available for this article. Go to the publisher's online edition of Journal of Occupational and Environmental Hygiene for the following free supplemental resource: tables documenting a description of areas and job titles in the database as well as a description of task bins and summary statistics for the task and nontask dataset.]

Notes

^A Six sample results above 1 ppm were collected in 1977 at the catalytic cracker, reformer (2), gas blending, pipestills and light ends unit areas.

^B Thirteen sample results above 1 ppm were collected in 1977 and 1984 at the fuels and analytical quality assurance laboratories

^C Maximum sample result collected in 1989 while blinds were removed from an undrained line containing gasoline.

^D Maximum sample result collected in 1978 at the pipestill.

^E Maximum sample result collected in 1977 at the waste water treatment plant.

^F Maximum sample result collected in 1980; no additional information was available

^G Maximum sample result collected in 1983 during inspection of exchanger shell.

^H Maximum sample result collected in 1992 during tank cleaning and liquid removal.

^I Maximum sample result collected in 1988; no additional information was available.

^J Twelve sample results above 1 ppm were collected between 1992 and 1995 in the tank farm area during cleaning tasks or where a worker was near the manway.

^K Maximum sample result collected in 1996 during cleaning out sludge from desalter.

^L Maximum result collected in 1996 during welding where there was a leak in the tower where work was occurring.

^M Two sample results above 1 ppm were collected in 1993 and 1995 during equipment draining at the catalytic cracker and pipestill units, respectively.

^N Includes 16 samples with unspecified job title.

^A Total does not include 55 samples where routine work was performed or there was insufficient data to assign a task bin.