Evaluation and Enhancement of the Performance of Benzene Solubles Methods for Asphalt Fume Assessment

Abstract

A laboratory study was conducted to determine which benzene soluble fraction (BSF) analytical method—National Institute for Occupational Safety and Health (NIOSH) Method 5023 or Occupational Safety and Health Administration (OSHA) Method 58—provides the best accuracy and precision at their lower limits of detection (LODs) for measuring asphalt fume exposures. In addition, the total hydrocarbon components of asphalt fume were determined in conjunction with NIOSH Method 5023 by introducing a large charcoal tube after the filter cassette. During an asphalt industry cross-sectional exposure assessment study [Appl. Occup. Environ. Hyg. 10(10):840-848 (1995)], it was determined that the NIOSH method lacked accuracy at very low airborne concentrations. It became evident that there were background problems at the LOD when BSF results were greater than the total dust results. Laboratory static and dynamic tests were conducted to determine if BSF background contamination occurs from the benzene used for extraction, from the extraction systems, or from the filters. Once the sources of background contamination were identified, a comparison of the two analytical methods was performed. The effect of storage on the different medium types (PTFE and glass fiber) was examined, and extraction efficiencies using mineral oil spikes and laboratory-generated fumes were determined. It was concluded that NIOSH Method 5023 with modifications to reduce the BSF background provided better accuracy and precision at the LOD than OSHA Method 58 at the concentration range from 0.2 to 5.0 mg/m³. In addition, the large charcoal tube in line with NIOSH Method 5023 successfully measured the volatile components of the fume for a complete assessment of the potential hazards.