p-Phenylenediamine-Derived Quinones as New Contributors to the Oxidative Potential of Fine Particulate Matter

Abstract

Atmospheric fine particulate matter (PM 2.5 ) has been linked to multiple adverse outcomes, where redox-active species-induced oxidative stress is recognized as an important driver of its biotoxicity. Previous studies have proven that the oxidative potential (OP) is a relevant metric for specific acute PM 2.5 health effects and is associated with various toxicants, especially organic quinones. However, discrepancies between OP induced by the known components and its total levels caused by PM 2.5 remain. Here, we investigated the OP values of a suite of emerging contaminants, five p-phenylenediamine-derived quinones (PPD-quinones), in PM 2.5 using the acellular dithiothreitol (DTT) assay and evaluated their contributions to the total PM 2.5 -induced OP in five megacities in China. N-(1,3-Dimethylbutyl)-N′-phenyl-p-phenylenediamine-quinone (6PPD-Q), a highly toxic quinone responsible for "urban runoff mortality syndrome", was found to exhibit moderate OP with a DTT consumption rate of 1.70 μM min −1 μM −1 . Meanwhile, it is noteworthy that the estimated OP contribution of the five PPD-quinones was 2.9 ± 2.7% of the total PM 2.5 -induced OP. This is the first study that reveals a considerable OP induced by the emerging PPD-quinones in urban PM 2.5 . The data improve our understanding of the toxicity of both PM 2.5 and PPD-quinones, which is illuminating for further assessment of the environmental risk they pose.

Screening p-Phenylenediamine Antioxidants, Their Transformation Products, and Industrial Chemical Additives in Crumb Rubber and Elastomeric Consumer Products

“…Notably, in addition to the commonly detected 6PPDQ, four other environmental PPDQs were frequently detected in these rubber products, especially the detections of DPPDQ and DTPDQ in crumb rubber at similar concentrations to 6PPDQ. These PPDQ detections again indicate that quinone TP formation may occur for many PPD antioxidants, producing PPDQs with as-yet unknown toxicity characteristics. ,, In addition to the quinone products, other interesting TPs of 6PPD were detected, including the bioactive stimulant 1,3-DMBA and the potentially carcinogenic nitroso-compound 4s DPA.…”

“…These PPDQ detections again indicate that quinone TP formation may occur for many PPD antioxidants, producing PPDQs with as-yet unknown toxicity characteristics. 17,18,21 In addition to the quinone products, other interesting TPs of 6PPD were detected, including the bioactive stimulant 1,3-DMBA and the potentially carcinogenic nitroso-compound 4s DPA.…”

“…IPPD showed 14-d LC 50 of 90 μg/L for fathead minnow ( Pimephales promelas ), although the stability of reactive PPD antioxidants throughout these longer term exposures remains unclear. Global reports now document PPD antioxidants and TPs, including the toxic 6PPDQ and quinones generated from other PPDs (PPDQs), ubiquitously in roadway-impacted air, − dust, − soil, and water, ,− with growing concern for the environmental dispersal, fate, and exposure implications of tire tread wear particles (TWPs) and associated chemicals …”

The Tire-Derived Chemical 6PPD-quinone Is Lethally Toxic to the White-Spotted Char Salvelinus leucomaenis pluvius but Not to Two Other Salmonid Species

“…The mechanisms of the acute lethality of 6PPD-Q to salmonids are still unclear, although the disruption of the blood–brain barrier, mitochondrial dysfunction, and oxidation were indicated as the key events that are responsible for the high toxicity of 6PPD-Q. ,, More research is needed to gain a comprehensive understanding of the mechanism by which 6PPD-Q can induce acute lethality to some salmonid species and to elucidate the causes of large interspecies differences in sensitivity. This study demonstrates the 6PPD-Q concentrations in brain and gill of insensitive salmonid species without apparent symptoms might be higher than those in the sensitive species S. leucomaenis pluvius showing mortality symptoms, which indicates that species sensitivity differences may be somewhat driven by toxicodynamic factors.…”

First Report on the Occurrence of N-(1,3-Dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) and 6PPD-Quinone as Pervasive Pollutants in Human Urine from South China

“…More recently, 6PPD and 6PPD-Q have been found in a variety of environmental matrices, including atmospheric particles, ,− indoor dust, ,, road dust, , playground dust, roadside soil, runoff water, ,, and surface water. − In most cases, 6PPD and 6PPD-Q coexisted in these environmental matrices at comparable concentrations. For instance, Zhang et al demonstrated ubiquitous distributions of 6PPD and 6PPD-Q in fine particulate matters (PM 2.5 ) from six Chinese cities, and the atmospheric concentrations of 6PPD (median 0.9–8.4 pg/m 3 ) were found to be similar to those of 6PPD-Q (median 1.7–6.7 pg/m 3 ) .…”