The quantification of exposures to diesel particulate matter (DPM) could be adversely affected by the presence of micron-sized aerosols in DPM samples containing organic and elemental carbon from other than combustion sources. Therefore, size classification plays an important role in the collection of representative DPM samples. The results of this evaluation were used to assess the potential for an improvement in the size separation of diesel and micron size aerosols by using lower cutoff-size impactors in DPM sampling cassettes. Three impactors with the cut-off diameters of 258, 466, and 716 nm were characterized in the laboratory using polystyrene divinylbenzene beads, and consequently the impactors were evaluated in the outby area of an underground coal mine incorporating diesel-powered equipment. Scanning electron microscope analysis of the field samples showed that reduction of the cut-off diameters of the impactors resulted in lower contamination of the DPM samples with micron-sized particulates, in this case primarily mineral dust. The total mass concentrations of organic and elemental carbon in the samples were found to be inversely affected by the cut-off size of the orifices, indicating some potential losses of DPM in the impactors with smaller cut-offs.
