Justin P. Miller-Schulze

Evaluation of urinary metabolites of 1-nitropyrene as biomarkers for exposure to diesel exhaust in taxi drivers of Shenyang, China.

Diesel exhaust (DE) is a significant contributor to the toxicity associated with particulate matter (PM). 1-Nitropyrene (1-NP) has been used as a molecular marker for DE, and the urinary metabolites of 1-NP have been proposed as biomarkers for exposure to DE. In this study, several urinary 1-NP metabolites were evaluated for their utility as markers of short-term exposures to DE. The study population was a cohort of 24 taxi drivers from Shenyang, China, who submitted urine samples collected before, after, and the next morning following their workshifts. The urinary metabolites studied were isomers of hydroxy-1-nitropyrene (3-, 6-, 8- OHNPs) and hydroxy-N-acetyl-1-aminopyrene (3-,6-, 8-OHNAAPs). Exposure to DE was estimated based on exposure to 1-NP in air samples collected during and after the drivers workshift; 6- and 8-OHNP, and 8-OHNAAP were consistently detected in the drivers’ urine. Concentrations of the metabolites in the taxi drivers’ urine were greater than metabolite levels previously reported in non-occupationally exposed subjects; however no associations were observed between subject-specific exposures to 1-NP and urinary metabolites measured at the end of the workshift or in the next morning void. Significant autocorrelation was observed in metabolite levels in successive urine samples, from which half-lives for urinary elimination of ∼10–12 h were estimated. These observations suggest that, in an occupational setting, urinary 1-NP metabolites may be more suitable as markers of ongoing exposure (timescales of several days) rather than indicators of acute exposure associated with single workshifts.

Evaluating Contaminants of Emerging Concern as tracers of wastewater from septic systems.

Bacterial and nutrient contamination from anthropogenic sources impacts fresh and marine waters, reducing water quality and restricting recreational and commercial activities. In many cases the source of this contamination is ambiguous, and a tracer or set of tracers linking contamination to source would be valuable. In this work, the effectiveness of utilizing a suite of Contaminants of Emerging Concern (CECs) as tracers of bacteria from human septic system effluent is investigated. Field sampling was performed at more than 20 locations over approximately 18 months and analyzed for a suite of CECs and fecal coliform bacteria. The sampling locations included seeps and small freshwater discharges to the shoreline. Sites were selected and grouped according to level of impact by septic systems as determined by previous field sampling programs. A subset of selected locations had been positively identified as being impacted by effluent from failing septic systems through dye testing. The CECs were selected based on their predominant use, their frequency of use, and putative fate and transport properties. In addition, two rounds of focused sampling were performed at selected sites to characterize short-term variations in CEC and fecal coliform concentrations, and to evaluate environmental persistence following source correction activities. The results indicate that a suite of common use compounds are suitable as generalized tracers of bacterial contamination from septic systems and that fate and transport properties are important in tracer selection. Highly recalcitrant or highly labile compounds likely follow different loss profiles in the subsurface compared to fecal bacteria and are not suitable tracers. The use of more than one tracer compound is recommended due to source variability of septic systems and to account for variations in the subsurface condition. In addition, concentrations of some CECs were measured in receiving waters at levels which suggested the potential for environmental harm, indicating that the possible risk presented from these sources warrants further investigation.

Nitro-PAH exposures of occupationally-exposed traffic workers and associated urinary 1-nitropyrene metabolite concentrations

The assessment of occupational exposure to diesel exhaust (DE) is important from an epidemiological perspective. Urinary biomarkers of exposure have been proposed as a novel approach for measuring exposure to DE. In this study, we measured the concentrations of two urinary metabolites of 1-nitropyrene (1NP), a nitrated polycyclic aromatic hydrocarbon that has been suggested as a molecular marker of diesel particulate matter. These two metabolites, 6-hydroxy-1-nitropyrene and 8-hydroxy-1-nitropyrene, were determined in urine samples (10mL) from a small group of workers who were occupationally-exposed to vehicle exhaust in Trujillo, Peru, before and after their workshifts. Workshift exposures to 1NP, as well as PM2.5, 2-nitropyrene and 2-nitrofluoranthene, were also measured. Exposures to 1NP were similar in all studied workers, averaging 105±57.9pg/m3 (±standard deviation). Median urinary concentrations of the average of the pre- and post-exposure samples for 6-hydroxy-1-nitropyrene and 8-hydroxy-1-nitropyrene, were found to be 3.9 and 2.3pgmetabolite/mg creatinine, respectively in the group of occupationally-exposed subjects (n=17) studied. A direct relationship between workshift exposure to 1NP and urinary 1NP metabolites concentrations was not observed. However, the 1NP exposures and the creatinine-corrected urinary concentrations of the hydroxynitropyrene metabolites in these Peruvian traffic workers were similar to occupationally-exposed taxi drivers in Shenyang, China, and were higher than biomarker levels in office workers from Trujillo without occupational exposure to vehicle exhaust. This study provides further evidence that urinary metabolites of 1NP are associated with exposure to DE and may serve as a useful exposure biomarker.