First assessment of the ecotoxicological effects of the tire antioxidant 6PPD on early life stages of the popular sport fish species, the largemouth bass (Micropterus nigricans)

N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) is a widely used rubber antioxidant, entering aquatic ecosystems through roadway runoff of tire wear particles. A transformation product of 6PPD, 6PPD-quinone, has been detected in watersheds at concentrations acutely toxic to some salmonid fish species. We evaluated the toxicity of 6PPD to early-life stage largemouth bass (Micropterus nigricans) in a series of outdoor aquatic microcosm experiments. Wild-collected embryos were chronically exposed to 6PPD and its potential transformation products in natural lake water under ambient environmental conditions. In a preliminary 96-h experiment, 6PPD was toxic to largemouth bass embryos with a 96-h LC50 of 42.8 µg/L. Interestingly, we found that exposure to 6PPD-quinone did not cause mortality in largemouth bass embryos beyond concentrations of maximum solubility in water. To further investigate the developmental toxicity of 6PPD, largemouth bass were exposed to 6PPD (modelled time-weighted average concentrations ranging from 0.1–3.7 µg/L) for 10 d, which spanned the embryonic to yolk-sac larval life stages. Exposure to 6PPD decreased yolk sac absorption as well as increased the occurrence and severity of malformations compared to the solvent control. As the first toxicological assessment of 6PPD with largemouth bass, our findings provide an important first step in understanding how 6PPD affects the development of the early life stages under environmentally realistic conditions.