There were nearly 20 million registered motor vehicles travelling 877,000 kilometres of Australian roads in 2020.  The rubber used in tyres contains various additives (e.g. antioxidants, binding agents, plasticizers) to improve manufacturing processes and product performance.  Abrasion of the tyre against the road surface generates tyre wear particles (TWPs), which are transported into urban watersheds via surface runoff. As additives are often not covalently bonded to the tyre polymers, they can readily partition out of TWPs and into the environment. In early 2021 a landmark study identified 6PPD-quinone, a degradation product of the tyre additive 6PPD, as the causative agent of recurring mass mortality events of coho salmon (Oncorhynchus kisutch) in Pacific Northwest North America.  The parent compound, 6PPD (N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine; CAS 793-24-8), is added to passenger and commercial vehicle tyre formulations as an antioxidant in concentrations up to 2% by weight.  Following exposure to ozone, 6PPD is rapidly transformed to the toxic 6PPD-quinone. Due to the ubiquitous presence of TWPs in the environment, including the use of tyre crumb in synthetic sports fields, there is potential for widespread environmental contamination of tyre constituents.
This study describes a liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) method for the analysis of 6-PPD, 6-PPD-quinone and related compounds such as hexamethoxymethyl melamine (HMMM) at trace (parts per trillion) concentrations. As a case study we explore the presence of tyre constituents in multiple environmental compartments, including tyre crumb, sediment and surface waters of the Lane Cove National Park and Lane Cove River, located nine kilometres north-west of Sydney, Australia.