Loren Kaehn, CSP
Project title: An Occupational Exposure Assessment at a Petroleum Refinery
Completed in: 2008
Petroleum refining is a complex process that may present numerous occupational health hazards. Risks include exposure to chronic and acute hazards, such as benzene and hydrogen sulfide. This study assessed occupational exposures of airborne chemical and noise hazards at a small petrochemical refinery. Refinery operators, maintenance, laboratory and support staff exposures were monitored during full shift, partial shift and short term periods, as workers conducted daily and non-routine tasks. Active and passive sampling techniques were used in accord with NIOSH and OSHA methods. The survey completed assessments of benzene(n=138; operator full shift 95th percentile = 0.03 ppm, 92.2% censored; maintenance full shift 95th percentile = 0.11 ppm, 86.2% censored; short term 95th percentile = 0.57 ppm, 84.5% censored), naphthalene (n=117, 100% censored) and total hydrocarbon (n=32; maintenance full shift 95th percentile = 306 ppm, 76.9% censored; short term exposure 95th percentile = 153 ppm, 46.9% censored) exposures. Hydrogen sulfide (n=281; operator full shift 95th percentile = 100% censored; maintenance full shift 95th percentile = 0.01 ppm, 92.9$ censored; short term 95th percentile = 0.02 ppm, 79.4% censored; and peak 95th percentile = 1.20 ppm, 76.23% censored) and sulfur dioxide (n=64; operator full shift 95th percentile = 0.03 ppm, 84.6% censored; maintenance full shift 95th percentile = 0.01 ppm, 85.7% censored; short term 95th percentile = 2.59 ppm, 31.8% censored; and peak 95th percentile = 15.9 ppm, 9.1% censored) personal direct reading instruments were used for gas exposures. The investigation evaluated mercury vapor exposures (n=126; operator full shift 95th percentile = 1 ug/m3, 94.7% censored; maintenance full shift 95th percentile = 3 ug/m3, 85.4% censored; partial shift 95th percentile = 9 ug/m3, 78.9% censored), as the facility periodically processed mercury-containing crude oils. Hexavalent chromium exposures were monitored during welding and cutting tasks (n=14; full shift TIG welding 95th percentile = 1.2 ug/m3 and full shift arc welding 95th percentile = 8.9 ug/m3). The evaluation monitored noise exposures of refinery staff (n=31; operator full shift Leq 95th percentile = 91.2 dBA; maintenance full shift Leq 95th eprcentile = 98.1 dBA). Additionally, samples were collected for acetone, aluminum, ammonia, arsenic, asbestos, cobalt, machining oils, methanolamine, silica, tetrachloroethylene and welding fumes. Worker exposures were compared to relevant occupational exposure limits and stratified according to the urgency for follow-up. Hexavalent chromium, sulfur dioxide and noise exposures necessitated additional control methods or follow-up. Site control methods, including ventilation modifications, equipment substitution, procedural changes and personal protective equipment were recommended to facility management and staff.