p-Phenylenediamine Antioxidants in PM_2.5: The Underestimated Urban Air Pollutants

Abstract

The wide use and continuous abrasion of rubber-related products appears to be leading to an incredible release of p-phenylenediamine (PPD) antioxidants in the environment. However, no related research has been conducted on the pollution characteristics and potential health risks of PM 2.5 -bound PPDs. We report for the first time the ubiquitous distributions of six emerging PPDs and a quinone derivative, N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine quinone (6PPDQ), in PM 2.5 from urban areas of China. Atmospheric contamination levels of PM 2.5 -bound PPDs were found to be mostly in pg m −3 amounts between 2018 and 2019. Urban vehicle rubber tire abrasion was found to probably contribute to the PPDs in PM 2.5 and accounted for their significant spatiotemporaldependent concentration variations. Furthermore, 6PPDQ, an emerging oxidation product of 6PPD in the environment, was first quantified (pg m −3 ) with a total detection rate of 81% in the urban PM 2.5 , demonstrating its broad existence. On the basis of the determined ambient concentrations, the annual intakes of PPDs and 6PPDQ for adults were not low, indicating their possible human health risks induced by long-term exposure. This study confirms the widespread occurrence of PPDs and 6PPDQ in PM 2.5 , showing that the pollution of such compounds in urban air should not be underestimated.

Beyond Substituted p-Phenylenediamine Antioxidants: Prevalence of Their Quinone Derivatives in PM2.5

“… 4 In another study, Zhang et al evaluated the level of PPDs in PM 2.5 among six different cities in China and found remarkable intercity distinctions. 7 Their results found that the levels of 77PD were comparable or even higher than 6PPD in the investigated six cities. Considering this, we speculated that 77PD-Q may also occur in PM 2.5 collected from highly polluted areas/cities.…”

“… 37 Our results are in line with these earlier studies and suggest that traffic intensity may be a possible factor affecting the emission of PPD-Qs to the environment. 7 , 13 …”

“…Emerged evidence indicated that these chemicals can be ubiquitously detected in receiving waters, 2 , 3 dusts, 4 , 5 sediments, 6 and air particles. 7 In parallel, detrimental effects of several broadly adopted PPDs have been reported. N, N ′-diphenyl- p -phenylenediamine (DPPD) was found to cause reproductive/developmental toxicity in rats.…”

Transformation Product Formation upon Heterogeneous Ozonation of the Tire Rubber Antioxidant 6PPD (N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine)

“…After environmental release, TWPs enter soils, sediments, or surface waters and become persistent contaminant sources, − including some extensively investigated contaminants like metals and PAHs. − Presently, knowledge concerning TWP-derived emerging contaminants and related transformation products (TPs) is fragmentary and incomplete, although researchers are gradually narrowing this gap. − Recently, 6PPD-quinone (6PPDQ), a TP of the common antioxidant 6PPD ( N -(1,3-dimethylbutyl)- N ′-phenyl- p -phenylenediamine), was reported to induce acute toxicity and mortality to coho salmon ( Oncorhynchus kisutch) at concentrations even below 100 ng/L. , To our knowledge, 6PPD is used in all passenger and commercial vehicle tires (0.4%–2% by rubber mass) to provide critical antiozonant and antioxidant functions at tire rubber surfaces. 6PPD and some related TPs, including 6PPDQ, were recently reported in roadway-derived particles and dusts. ,,,− Given the global ubiquity of TWPs in roadway runoff and surface waters , and their toxicological relevance, , there exists an urgent need to characterize TWP-derived TPs.…”

E-Waste Recycling Emits Large Quantities of Emerging Aromatic Amines and Organophosphites: A Poorly Recognized Source for Another Two Classes of Synthetic Antioxidants

“…Recently, a quinone derivative of the tire rubber antioxidant N -(1,3-dimethylbutyl)- N ′-phenyl-PPD (6PPD) formed by oxidative transformation, termed 6PPD-quinone, has attracted considerable international attention on PPDs because 6PPD-quinone was identified as the toxicant responsible for acute mortality in the Pacific Northwest coho salmon . Subsequent studies have confirmed the ubiquitous occurrence of 6PPD and 6PPD-quinone in stormwater runoff, surface waters, air particles, and dust. − The same pathway may also produce quinones from other PPDs. A more recent study provided new evidence of multiple PPD-derived quinones in environmental media .…”