258 An evaluation of respirable and submicron elemental carbon measured using the NIOSH analytical method 5040 in low concentration diesel environments

Airborne particles containing diesel particulate matter (DPM) continue to be a focus of scientific and regulatory interest. Assessing the effectiveness of sampling devices for respirable and submicron DPM in low-concentration environments (e.g., < 20 µg/m3) is essential as authoritative standards and guidance organizations begin to develop occupational exposure limits (OELs) for DPM. Much of the current research and method development is focused on sampling DPM in underground mines due to their limited ventilation and restricted space. In the present study, the National Institute of Occupational Safety and Health Method 5040 (modified for respirable and submicron) elemental carbon (EC) was used to determine if EC would be detectable in low-concentration environments using currently available sampling equipment. Sixty-three samples were collected in locomotive mechanical shops and a truck stop using 3 different side-by-side samplers to simultaneously collect total, respirable and submicron fractions of EC. A standard 37-mm cassette was used for the total fraction of EC (TEC), a 25-mm cassette equipped with a respirable dust cyclone (GK 2.69) was used for the respirable fraction of EC (REC), and a SKC diesel particulate cassette (SKC P225317) was used to collect the submicron fraction of EC (SMEC). The geometric mean (GM) for the TEC samples was 1.75 µg/m3. The geometric mean (GM) for the REC samples was 0.2 µg/m3. The GM for the SMEC samples could not be calculated because 100% of the samples were below the limit of detection (LOD). Results demonstrate the need for a better sampling device that can achieve a detectable level of submicron DPM in low concentration environments.