Abstract:
Diesel engines are used all over the world in many different applications. Diesel exhaust (DE) has been shown to be associated with several adverse health effects, the most notable being lung cancer. Current methods of measuring exposure to DE use elemental carbon (EC) as an exposure surrogate, but EC is also formed by biomass burning, gasoline engines, and other sources which makes accurate measurement in environmental conditions difficult. 1-Nitropyrene (1-NP) is a chemical that is specific to DE, and with new analytical methods, can be detected at much lower concentrations. The goal of this study is to determine the relationship between personal 1-NP, and personal EC exposures, and how well personal exposures can be predicted from area monitoring in a metal mine. Exposures to 1-NP and EC were measured for a cohort of workers in a metal mine for 4 work days during March 2014. 1-NP samples were collected with GS-1 respirable cyclones, and EC was collected using SKC DPM impactors. Personal monitors for both 1-NP and EC were used during the work shift as well as 4 fixed location area monitors which were placed throughout the mine and in the above ground office space. In addition to personal air monitoring, surveys were given to the miners which asked about the job tasks that the miners were performing throughout the day. The 1-NP filters were analyzed using a 2D HPLC MS/MS method and the EC filters were analyzed using evolved gas analysis (EGA) by thermal-optical analyzer. Due to the nature of the mine, area samples were not able to be used as predictors of personal exposures. A 1-NP outlier was found with an exposure of 5380pg/m3. This outlier was 10-fold higher than all other 1-NP exposures while the associated EC exposure was only 11µg/m3. The log transformed 1-NP exposures were found to be associated with log EC exposures (p<0.001, R2=0.45) even with the small sample size collected in the study. Based on these results, additional research is needed to understand outlying exposures, but 1-NP is indeed correlated with the current EC measures of DE exposure. Improved surrogates such as 1-NP provide a more specific measure of diesel exhaust, and may be useful in situations where using EC as a surrogate is not feasible. In addition, the use of 1-NP also opens up the possibility of using metabolites of 1-NP as human exposure biomarkers.