UC Irvine

Recent toxicity studies of stormwater runoff implicated N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone (6PPD-quinone) as the contaminant responsible for the mass mortality of coho salmon (Oncorhynchus kisutch). In the wake of this discovery, 6PPD-quinone has been measured in waterways around urban centers, along with other tire wear leachates like hexamethoxymethylmelamine (HMMM). The limited data available for 6PPD-quinone have shown toxicity can vary depending on the species. In this study we compared the acute toxicity of 6PPD-quinone and HMMM to Brook trout (Salvelinus fontinalis) fry and fingerlings. Our results show that fry are ∼3 times more sensitive to 6PPD-quinone than fingerlings. Exposure to HMMM ≤ 6.6 mg/L had no impact on fry survival. These results highlight the importance of conducting toxicity tests on multiple life stages of fish species, and that relying on fingerling life stages for species-based risk assessment may underestimate the impacts of exposure. 6PPD-quinone also had many sublethal effects on Brook trout fingerlings, such as increased interlamellar cell mass (ILCM) size, hematocrit, blood glucose, total CO2, and decreased blood sodium and chloride concentrations. Linear relationships between ILCM size and select blood parameters support the conclusion that 6PPD-quinone toxicity is an outcome of osmorespiratory challenges imposed by gill impairment.