Environmental Occurrence and Toxicity of 6PPD Quinone, an Emerging Tire Rubber-Derived Chemical: A Review

Abstract

-N′-phenyl-p-phenylenediamine (6PPD) is a chemical added to tires to prevent their oxidative degradation. 6PPD is highly reactive with ozone and oxygen, leading to the formation of transformation products such as 6PPD quinone (6PPDQ) on the tire surfaces and, subsequently, in tire and road wear particles. 6PPDQ is a toxicant that has been found in roadway runoff and receiving water systems. Its presence in municipal stormwater has led to the acute mortality of coho salmon during their migration to urban creeks to reproduce, generating global interest in studying its occurrence and toxicity in the environment. This review aims to provide a critical overview of the current state of knowledge of 6PPDQ, assisting researchers and policymakers in understanding the potential impacts of this emerging chemical on the environment and human health. As there are many unanswered questions surrounding 6PPDQ, further research is needed. This review highlights the importance of including transformation products in regulations for 6PPD, as well as all emerging synthetic chemicals of concern.

Screening of Tire-Derived Chemicals and Tire Wear Particles in a Road Tunnel Wash Water Treatment Basin

“…Our study reported higher concentrations of 6PPD-Q compared to those found in urban runoff from Hong Kong (210–2430 ng/L) and road runoff from Huizhou and Dongguan (38.5–1562 ng/L) . The concentrations of 6PPD were much higher than those reported elsewhere, e.g., 300–14 300 ng/L in a German wastewater treatment plant and 21–130 ng/L in road runoff from Pierce County (USA) . According to Zhou et al, the presence of organic matter and sunlight may enhance the formation of 6PPD-Q in a continuous manner.…”

Tracking Aromatic Amines from Sources to Surface Waters

“…89,90 Given the growing concern regarding tire rubber-derived chemicals and their transformation products, these compounds have received attention in recent dedicated reviews. 17,18,91,92 Tobacco Smoke. Tobacco smoke contains a complex mixture of chemicals, including AAs, which are formed during the combustion of tobacco leaves.…”

“…85,86,191,192 However, most of these studies are limited to method validation, and extensive screenings have not been done. There is growing literature covering tire rubber-associated AAs in surface waters 17,18 given the particular concern about their aquatic toxicity, 80 and increases in surface water concentrations of tire rubberassociated AAs are documented during rain events, which suggests a clear pathway from surface runoff to surface waters. 82 Outside of surface water, quantitative information about AAs is even more limited.…”

“…While a focus for much work on AAs has been industrial WW, broader efforts are needed to enhance our understanding of environmental contamination by mutagenic AAs from multiple matricesfrom the indoor environment through to outdoor air, surfaces, WW, and surface water. Recent work targeting specific AA tire additives, notably N ‑(1,3-dimethylbutyl)- N ′-phenyl-1,4-benzenediamine (6PPD), − has highlighted the importance of AA emissions to aquatic systems from product use. A comprehensive evaluation of AAs necessitates tools and sampling strategies to support the source identification of AAs and probable pathways of entry to the environment.…”

Assessment of Tire-Additive Transformation Product 6PPD-Quinone in Urban-Impacted Watersheds

“…Urban air particulate containing tire dusts and dusts from indoor environments, particularly those from facility recycling rubber and electronic waste facilities, also contain 6PPD-Q. Recent reviews summarize the rapidly increasing state of knowledge on sources and levels of 6PPD-Q, its toxicity, and fate. − …”