Occurrences of Tire Rubber-Derived Contaminants in Cold-Climate Urban Runoff

Recent findings that
2-anilo-5-[(4-methylpentan-2-yl)­amino]­cyclohexa-2,5-diene-1,4-dione
(6PPD-quinone), the transformation product of a common tire rubber
antioxidant, is acutely toxic in stormwater-impacted streams has highlighted
the need for a better understanding of contaminants in urban runoff.
This study represents one of the first reports of 6PPD-quinone and
other tire rubber-derived compounds in stormwater and snowmelt of
a cold-climate Canadian city (Saskatoon, 2019–2020). Semiquantification
of the five target compounds, N,N′-diphenylguanidine (DPG),
N,N-dicyclohexylmethylamine (DCA), N,N′-dicyclohexylurea (DCU),
1-cyclohexyl-3-phenylurea (CPU), and 6PPD-quinone, revealed DPG was
most abundant, with average concentrations of 60 μg L–1 in stormwater and 1 μg L–1 in snowmelt.
Maximum observed concentrations of DPG were greater than 300 μg
L–1, equivalent to loadings of 15 kg from a single
rain event. These concentrations of DPG represent some of the highest
reported in urban runoff globally. 6PPD-Quinone was detected in 57%
(12/21) of stormwater samples with a mean concentration of approximately
600 ng L–1 (2019) and greater than 80% (28/31) of
snowmelt samples with mean concentrations of 80–370 ng L–1 (2019 and 2020). Concentrations of 6PPD-quinone exceeded
the acute LC50 for coho salmon (0.8–1.2 μg
L–1) in greater than 20% of stormwater samples.
Mass loadings of all target chemicals correlated well with roads and
residential land-use area.