Diesel exhaust is a known carcinogen and has been linked to several negative health outcomes, yet it is commonly used in industrial settings such as underground mining. Alternative fuels such as GDiesel® (GD), a natural gas/diesel blend, have the potential to reduce health exposures and associated health effects. Mirroring a previous study in which use of GD in a 2005 Wagner load-haul-dump (LHD) vehicle with oxidation catalyst demonstrated significant reductions in diesel exhaust exposures, operator-location and area exposure samples were collected in an underground mining laboratory with diesel (D) and then GD fuel while operating a JCI LHD. Analytes of interest included total and respirable diesel particulate matter (tDPM and rDPM, respectively), total and respirable elemental and organic carbon (tEC, rEC, tOC, rOC, respectively), as well as formaldehyde (CH2O), nitric oxide (NO), and nitrogen dioxide (NO2). Use of GD resulted in non-significant reductions in median rOC, tDPM, tOC, and NO2 concentrations, non-significant increases in rDPM, rEC, tEC, and NO, and identical median CH2O concentrations. A significant decrease in NO2 exposure concentrations (p=0.012) and increase tEC and rEC exposure concentrations (p=0.023 and p=0.024, respectively) were observed. After controlling for environmental confounders there was no difference observed in analyte concentrations between the two fuels. Further research is needed to determine whether GD alone can significantly reduce human exposures across vehicles and pollution configuration types.

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.

Diesel equipment exhaust is a primary source of carbon-rich submicron particles in the underground mine atmosphere. In this study, the characterization of the morphological and physical properties of particles was used for identification of emission source and understanding the effect of diesel particulate matter (DPM) controll strategies on DPM characteristics. The size distributions and other physical properties of diesel aerosol were investigated on size-segregated samples collected in an underground mining operation. Scanning transmission electron microscopy (STEM) and fast mobility particle sizer were used concurrently to investigate size distribution based on particle projected area and electrical mobility. Other morphological attributes, such as fractal dimension, carbon net counts, and primary particle dimensions were examined for light and heavy-duty equipment powered by for various engine sizes. The results of STEM analysis showed presence of three types of chain-like agglomerates as well as volatile carbon particles. The results showed that when used concurrently, real-time and microscopic techniques can provide a wealth of information on characteristics of aerosols in underground atmosphere. 

The introduction of diesel particulate filters (DPF) technology has been an important step towards controlling diesel emission from heavy-duty diesel -powered underground mining vehicles. The Johnson Matthey CRT® (Continuously Regenerating Trap) technology that combines a diesel oxidation catalyst (DOC) with a DPF has be extensively used to trap harmful diesel aerosols, CO and hydrocarbons from on-road vehicles. In order to address concerns over adverse effects of CRT® system on NO₂ emissions and allow for use of these systems in underground mining environments, Johnson Matthey (JM) developed, the Mining CRT® system which integrates CRT® technology with NO₂ abatement components. The effects of the system on particulate and gaseous emissions were evaluated in the engine dynamometer laboratory. The evaluation was done using Caterpillar C11, Tier 3 engine operated over the ISO 8178, 8-mode test cycles. The engine was fueled with an ultra–low-sulfur diesel fuel. The system was found to effectively reduce total particulate mass and number, total hydrocarbon, and CO emissions. The novel fuel injection and NO₂ decomposition catalyst were found to be effective in preventing NO₂ slip out of the system.