Student Research: Emily Carpenter

, Occupational & Environmental Exposure Sciences (OEES), 2015
Faculty Advisor: Christopher D. Simpson

Evaluation of 1-Nitropyrene as a Surrogate Measure for Diesel Exhaust: Assessment of Personal Air Monitoring Data from an Underground Mine


Abstract

Objectives: We will investigate the hypothesis that 1-Nitropyrene (1-NP) concentration in air is a viable surrogate measure of diesel exhaust exposure, as compared with industry-standard elemental carbon (EC) and total carbon (TC) measurements. 1-NP content in personal air samples was measured for a cohort of underground miners and compared with measures of Elemental Carbon (EC), Organic Carbon (OC), and Total Carbon (TC) in the same samples.

Methods: Personal exposure data were collected on a cohort of 20 employees at a large underground metal mine during 4 different sample campaigns. Full-shift personal sampling was conducted using both an MSHA compliant SKC DPM impactor downstream of a GS-1 cyclone pre-filter, and a PTFE filter downstream of a GS-3 cyclone. Each DPM filter element was analyzed for EC and OC using NIOSH method 5040. Each PTFE filter was extracted with methylene chloride and analyzed for 1-NP using an LC/MS/MS method. Additionally, after EC and OC analysis each DPM filter was extracted with methylene chloride and analyzed for 1-NP using the LC/MS/MS method.

Results: 1-NP analysis of data from nine cascade impactors indicates that the smallest size fraction of particles, <0.25 µm, contains a majority of 1-NP mass (90% average). Regression analysis of 1-NP vs. EC yields an 8.7% increase in geometric mean (GM) 1-NP for each 10% increase in GM EC (p<0.001), and a 10.9% and 13.3% increase in GM 1-NP per 10% increase in GM OC and TC (p=0.007 & p<0.001, respectively).

Conclusions: 1-NP is found primarily in the respirable particles <0.25 µm, consistent with the known size distribution of diesel exhaust particles. The MSHA compliant SKC DPM impactor has a cut-point of 0.8 µm, and is expected to capture the majority of 1-NP-containing particles present in the mine. Additionally, 1-NP was found to be associated with EC, OC, and TC in personal air samples.