Particles Surface Area and Mass Concentration as Exposure Metrics for Diesel Particulate Matter Aerosol in US Underground Mines

EMANUELE CAUDA, Arthur Miller

US Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Office of Mine Safety and Health Research, 626 Cochrans Mill Road, Pittsburgh, PA 15236, USA.

     Abstract Number: 687
     Last modified: May 14, 2010

Abstract
Diesel Particulate Matter (DPM) exposure limits in United States metal/non metal mines are based on the measurement of size-specific mass concentration of total carbon (TC) and elemental carbon (EC). Several strategies are employed to reduce DPM concentration including adoption of exhaust aftertreatment control strategies, and the use of biodiesel blends. These strategies have been found effective in reducing the mass concentration of TC and EC, but their impact on the particle number concentration is more controversial. Moreover, how these control strategies affect the emission of DPM nanoparticles is another issue under current investigation.
For these reasons, the DPM emitted by diesel engines in underground mines is a ”new” DPM, with reduced mass concentrations, changing size distributions and evolving physical and chemical characteristics. The current metric might be not capable of completely assessing the exposure to this “new” DPM. This study explored the adoption of total surface area (TSA) of the particles as an additional metric to assess the exposure to DPM in underground mines. The total surface area of the DPM particles has been tested against the current metric used in underground mines based on mass concentration measurement. The study was carried out in a controlled environment exposure chamber connected to the exhaust of a diesel engine. Real time TSA levels were measured by using two diffusion charger monitors, while EC and TC mass concentrations were obtained via thermo optical analysis of collected DPM samples (NIOSH 5040). The results of this study have been used to define the range of applicability and the detection limits of the metric with regards to the DPM currently present in underground mines. This is the first attempt to adopt the TSA as an exposure metric in an occupational setting.