Employee exposure to diesel exhaust in the electric utility industry

The purpose of this study was to assess diesel exhaust exposures in the electric utility industry and to compare these findings with worker exposures reported in other industries and to proposed and established occupational exposure limits. Two sampling approaches were used: particulates were analyzed for elemental (EC) and organic (OC) carbon via the thermal-optical method; and gaseous components (NO2, SO2, NO, and CO) were determined using a direct reading instrument, the Metrosonics pm-7400. Concentrations of the gases were all well within established occupational exposure levels. The EC percentage of the total carbon was generally lower than results reported from other studies resulting in OC levels representing a higher percentage of the total carbon concentrations. Smokers had higher average OC exposure (79 micrograms/m3) than nonsmokers (57 micrograms/m3), but cigarette smoke did not contribute to EC levels in this study (smokers and nonsmokers = 3 micrograms/m3). Two of 120 individual personal exposure levels were found to exceed the proposed threshold limit value of 150 micrograms/m3 for total particulate, but geometric mean levels were found to be significantly less than the proposed value. Questions are raised concerning the use of EC as the sole surrogate for estimating diesel content for comparison with an exposure standard.