Gasoline Vapor Exposures. Part I. Characterization of Workplace Exposures

Abstract

Monitoring surveys of gasoline vapor exposures were conducted on truck drivers and terminal operators from five terminal loading facilities, on dockmen and seamen at two tanker/barge loading facilities, and on attendants at a single expressway service plaza. Results revealed wide variations in total hydrocarbon exposures for each location, with overall 8-hr time-weighted averaged (TWA®) geometric means of 5.7 mg/m3 (1.4 ppm) for the terminals, and 4.0 mg/m3 (1.0 ppm) for the service plaza, respectively. The exposures ranged from 0.8 to 120.8 mg/m3 (0.2–30.1 ppm) for the terminals, and from 1.1 to 130.3 mg/m3 (0.3–32.5 ppm) for the service plaza. For the terminals, exposures were not significantly different regardless of loading method or the presence or absence of vapor recovery systems. Comprehensive chemical analyses of terminal employee exposure samples revealed that the C4 and C5 hydrocarbon components constituted 74.8 ± 9.2% of the total exposure sample on a µg/sample basis. The C6, C7, and components constituted 13.0 ± 1.9, 6.2 ± 3.0, and 5.9 ± 7.2% of the total samples, respectively. Comprehensive analyses of the marine employee exposure samples resulted in a similar distribution of components; that is, 66.6 ± 7.9, 17.5 ± 4.7, 9.2 ± 3.1, and 6.4 ± 1.9% for the C4/C5, C6, C7, and components, respectively. The composition of the exposures, however, was weighted more toward the C5, C6 and C7 components when compared to the bulk terminal employee exposures. The analyses for both the terminal and marine loading exposures also revealed that four C4/C5 components — namely, n-butane, isobutane, n-pentane, and isopentane — comprised 90 to 92% of all the C4/C5 vapor components and approximately 61 to 67% of the total gasoline vapor samples. The composition of hydrocarbon constituents and their relative proportion in gasoline vapors appeared to remain fairly constant regardless of differences in gasoline blends, monitoring conditions, or magnitude or length of exposure. The geometric mean exposure to benzene through gasoline vapors was 0.8 mg/m3 (0.3 ppm) for the terminal employees, 0.5 mg/m3 (0.2 ppm) for the marine loading employees, and 0.7 mg/m3 (0.2 ppm) for the service station attendants oh an 8-hr TWA basis.