Abstract
Occupational exposure to diesel exhaust aerosols in mining and other industries was reviewed. The review described current diesel emissions standards and currently used techniques for measuring diesel exhaust aerosols and discussed the results of studies evaluating industrial exposures to diesel exhausts. Diesel exhaust is a complex chemical mixture. Permissible exposure limits (PELs) were established for a few constituents such as carbon-dioxide (124389), carbon-monoxide (630080), formaldehyde (50000), nitrogen oxides, and sulfur-dioxide (7446095). There was no specific United States PEL for diesel particulate matter (DPM). Some PELs also existed for polycyclic aromatic hydrocarbons, which are closely associated with DPM. Diesel exhaust exposures are measured primarily using three analytical techniques. Measuring the quantity of respirable combustible dust by a gravimetric technique following combustion at 500 degrees was used to measure DPM concentrations in Canadian coal mines. Size selective sampling in combination with gravimetric analysis was used to determine DPM in aerosols having particles with aerodynamic diameters smaller than 0.8 micrometer. This technique has been widely used to determine the concentrations of respirable dusts and DPM in mine atmospheres and to evaluate the performance of emission control devices. Elemental carbon because it constitutes a significant fraction, on the order of 40 to 60%, of DPM emissions is a useful surrogate for DPM. Elemental carbon is determined by a temperature based thermal optical method. The occupational surveys have investigated diesel exhaust exposures in mine workers, forklift operators, firefighters, and truck drivers. The level of DPM exposures measured in the surveys varied from 0.004 to 1.74mg/m3. The highest exposures were found in confined spaces such as in mines where heavy diesel equipment was used and fresh air was supplied by forced ventilation. Across all workplaces, the occupational exposures to DPM were generally much higher that outdoor ambient exposures.
