Immunochemical detection of metabolites of parent and nitro polycyclic aromatic hydrocarbons in urine samples from persons occupationally exposed to diesel exhaust

Urinary metabolites of 1-nitropyrene in US-Mexico border residents who frequently cross the San Ysidro Port of Entry

Diesel exhaust presents a community exposure hazard, but methods to measure internal exposure are lacking. We report results from a community-based study using 1-nitropyrene (1-NP) and its urinary metabolites as markers of exposure to traffic-related diesel particulate matter (DPM). The study participants were Tijuana, Mexico residents who commuted on foot into San Diego, California for work or school using the International San Ysidro Port of Entry, placing them within feet of idling traffic (referred to as border commuters). The comparison group (non-border commuters) was comprised of residents of south San Diego who did not commute into Mexico. Air concentration of 1-NP in fine particulate matter (PM_2.5) was measured in personal samples from participants. Spot urine samples were analyzed for 1-NP urinary metabolites 8-hydroxy-1-nitropyrene (8-OHNP) and 8-hydroxy-N-acetyl-1-aminopyrene (8-OHNAAP). Compared with non-border commuters, border commuters had two- to threefold higher mean urinary concentrations for unadjusted and creatinine-adjusted 8-OHNP and 8-OHNAAP. Urinary 8-OHNAAP and the sum of 8-OHNP and 8-OHNAAP were both associated with personal exposure to 1-NP in the prior 24 h. These results suggest that 1-NP urinary metabolites reflect recent exposure to DPM-derived 1-NP in community settings and can be useful for exposure analysis.

Urinary polycyclic aromatic hydrocarbon metabolites as biomarkers of exposure to traffic-emitted pollutants

1-Nitro-pyrene has been considered a compound specific to diesel combustion emission, while 1- and 2-nitro-napthalene are mainly produced through photochemical conversion of naphthalene released to the atmosphere. Metabolites of these compounds may serve as biomarkers of exposure to traffic related pollutants. We collected urine samples from 111 healthy and non-smoking subjects within (i.e., during the Beijing Olympics) and outside (i.e., before and after the Olympics) a traffic control regime to improve Beijing's air quality. Urines were analyzed for the sum of 1&2-amino-naphthalene (metabolites of 1- and 2-nitro-naphthalene) and 1-amino-pyrene (a metabolite of 1-nitro-pyrene), using an HPLC-fluorescence method. Within the same time periods, PM2.5 mass and constituents were measured, including elemental carbon, sulfate, nitrate, PAHs, carbon monoxide, nitrogen dioxide, sulfur dioxide, ozone, and particle number concentrations. The associations between the urinary metabolites and air pollutants were analyzed using linear mixed-effects models. From the pre- to during-Olympic period, 1&2-amino-naphthalene and 1-hydroxy-pyrene decreased by 23% (p=0.066) and 16% (p=0.049), respectively, while there was no change in 1-amino-pyrene (2% increase, p=0.892). From during- to post-Olympic period, 1&2-amino-naphthalene, 1-amino-pyrene and 1-hydroxy-pyrene concentrations increased by 26% (p=0.441), 37% (p=0.355), and 3% (p=0.868), respectively. Furthermore, 1&2-amino-naphthalene and 1-hydroxy-pyrene were associated with traffic related pollutants in a similar lag pattern. 1-amino-pyrene was associated more strongly with diesel combustion products (e.g. PN and elemental carbon) and not affected by season. Time-lag analyses indicate strongest/largest associations occurred 24-72h following exposure. 1&2-amino-naphthalene and 1-hydroxy-pyrene can be used as a biomarker of exposure to general vehicle-emitted pollutants. More data are needed to confirm 1-amino-pyrene as a biomarker of exposure to diesel combustion emissions. Controlling creatinine as an independent variable in the models will provide a moderate adjusting effect on the biomarker analysis.

Determination of 1-nitropyrene with enzyme-linked immunosorbent assay versus high-performance column switching technique

An enzyme-linked immunosorbent assay (ELISA) on microplates and a HPLC coupled-column switching method were compared for the determination of the nitroarene compound 1-nitropyrene in airborne particulate organic matter collected at a busy intersection over a period of 2 months. After purification of the sample extract with silica, in the multidimensional chromatographic method nitroarenes were separated on a RP18 precolumn from matrix constituents followed by on-line reduction to corresponding aminoarenes with a Pt catalyst on alumina and a further separation of 1-aminopyrene on a second RP18 column. Methanol-water (70:30, v/v) was the mobile phase used. With ELISA, a six-fold overestimation was obtained for untreated samples. After clean-up it was lowered to approximately 1.6-fold overestimation which was mainly caused by cross-reaction of 2-nitropyrene and 2-nitrofluoranthene.