1 Water Quality Centre, Trent University, Peterborough, ON, Canada; Department of Chemistry and Biochemistry, Concordia University, Montreal, QC, Canada. Electronic address: cjohannessen@trentu.ca.
2 Air Quality Processes Research Section, Environment & Climate Change Canada, Toronto, ON, Canada.
3 Department of Chemistry and Biochemistry, Concordia University, Montreal, QC, Canada.

Pollution from vehicle tires has received world-wide research attention due to its ubiquity and toxicity. In this study, we measured various tire-derived contaminants semi-quantitatively in archived extracts of passive air samplers deployed in 18 major cities that comprise the Global Atmospheric Passive Sampling (GAPS) Network (GAPS-Megacities). Analysis was done on archived samples, which represent one-time weighted passive air samples from each of the 18 monitoring sites. The target analytes included cyclic amines, benzotriazoles, benzothiazoles, and p-phenylenediamine (PPD) derivatives. Of the analyzed tire-derived contaminants, diphenylguanidine was the most frequently detected analyte across the globe, with estimated concentrations ranging from 45.0 pg/m³ in Beijing, China to 199 pg/m³ in Kolkata, India. The estimated concentration of 6PPD-quinone and total benzothiazoles (including benzothiazole, 2-methylthio-benzothiazole, 2-methyl-benzothiazole, 2-hydroxy-benzothiazole) peaked in the Latin American and the Caribbean region at 1 pg/m³ and 100 pg/m³, respectively. In addition, other known tire-derived compounds, such as hexa(methoxymethyl)melamine, phenylguanidine, and various transformation products of 6PPD, were also monitored and characterized semi-quantitatively or qualitatively. This study presents some of the earliest data on airborne concentrations of chemicals associated with tire-wear and shows that passive sampling is a viable strategy for monitoring airborne tire contamination. Due to the presence of many tire-derived contaminants in urban air across the globe as highlighted by this study, there is a need to determine the associated exposure and toxicity of these chemicals to humans.