Exposure assessment of benzene in the Swedish refinary industry

Introduction
Refinery workers are exposed to a mixture of hydrocarbons, including the human carcinogen benzene (IARC group 1). The aim of this study was to make a retrospective exposure assessment for different job titles in three refineries (1-3), located on the west coast of Sweden, as a part of a cohort cancer study.

Methods
Measurement reports from the three refineries together with published articles regarding benzene exposure in the European refineries (Concawe 1984-85, 1986-92, 1993-98) have been collected and evaluated for different job categories. An expert group was formed including occupational hygienists and knowledgeable personnel (safety engineers with long experience) from the three refineries. Discussions were held within the expert group regarding the collected material and how different technical innovations and improvements throughout the years had affected the benzene exposure in different job categories. A retrospective exposure assessment was performed for operators, laboratory personnel and maintenance workers on the refineries.

Results
In refinery 1-3, the operators’ mean benzene exposure was assessed to be about 7 mg/m3 prior to 1975, 3.5 mg/m3 between1975-88, 1 mg/m3 1989-90, 0.2 mg/m3 1991-2000 and 0.1 mg/m3 after 2001 until 2005. The benzene exposure of maintenance workers was assessed to be 50 % of the exposure of an operator in all of the three refineries. At refinery 1 and 2 the mean benzene exposure for laboratory personnel was assessed to be 0.05 mg/m3 from the beginning until 2005. In refinery 3 the exposure was higher; 3.5 mg/m3 between 1965-75, 0.5 mg/m3 1976-80, 0.1 mg/m3 1981-85, and similar to the others after 1986, 0.05 mg/m3. Recent personal measurements have shown much lower benzene exposure for all categories.

Discussion
The occupational benzene exposure of operators, laboratory personnel and maintenance workers at refineries has decreased over the years due to technical innovations and improvements, measurement programs and increased awareness.