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

Abstract

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 driver's 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.

Short-Term Traffic-Related Exposures and Biomarkers of Nitro-PAH Exposure and Oxidative DNA Damage

“…No dose-response was established, however, and determining a clear window of internalized exposure and appearance of the metabolites could be challenging given the large between person variability in marker levels and kinetics observed [17, 33]. The same limitations were observed in a study of other nitropyrene metabolites in taxi drivers occupationally exposed to diesel exhaust [41]. An earlier study reported no significant difference of 1-AP levels in blood, between small samples of workers occupationally exposed to diesel exhaust, and urban and rural populations [15].…”

Evaluation of 1-Nitropyrene as a Surrogate Measure for Diesel Exhaust

“…In addition to the value of direct measurement of 1-NP exposure in air as a surrogate measure of DE exposure, air measurements of 1-NP could be useful to validate biomarkers of exposure to DE including measurements of 1-NP metabolites in urine (a measure of dose aggregated across multiple exposure pathways) (Seidel et al, 2002;Toriba et al, 2007;Miller-Schulze et al, 2013;Morgott, 2014) or measurements of hemoglobin adducts to 1-aminopyrene (a measure of bioactivation that may lead to genotoxic effects) (van-Bekkum et al, 1997;Zwirner-Baier and Neumann, 1999). Moreover, as many of the nitro-arenes, including 1-NP, are mutagenic and carcinogenic (IARC, 2014), measurements of 1-NP and its metabolites may better reflect the carcinogenic properties of DE (Scheepers et al, 1995) and personal susceptibility factors such as polymorphisms in enzymes affecting nitroarene metabolism.…”

Recent analytical methods for atmospheric polycyclic aromatic hydrocarbons and their derivatives

“…This report was the first to demonstrate the presence of OHNAAPs and OHNPs in human urine. The measurement of urinary 1‐NP metabolites was applied in taxi drivers' urine samples collected in China, and their concentrations were greater than metabolite levels previously reported in non‐occupationally exposed subjects (Miller‐Schulze et al, ). The sum of urinary 1‐NP metabolites was associated with personal exposure to 1‐NP and the results suggested that the metabolites reflect recent exposure (Galaviz et al, ).…”