N-(1,3-Dimethylbutyl)-N′-phenyl-p-phenylenediamine-quinone (6PPD-quinone), a transformation
product of the rubber tire antioxidant 6PPD, has recently been identified
as the chemical responsible for urban runoff mortality syndrome in
coho salmon, with a median lethal concentration (LC50)
of <0.1 μg/L. Subsequent studies have failed to confirm comparable
sensitivity in other fish species. Here, we investigated the acute
toxicity of 6PPD-quinone to rainbow trout, brook trout, Arctic char,
and white sturgeon. Fish were exposed under static renewal conditions,
and exposure concentrations were verified analytically. Mortalities
in brook trout occurred between 1.2 and 20 h, while mortalities began
after 7 h and spanned 60 h in rainbow trout. The LC50s
in brook trout (24 h) and rainbow trout (72 h) were 0.59 and 1.00
μg/L, respectively. Both species showed characteristic symptoms
(increased ventilation, gasping, spiraling, and loss of equilibrium)
shortly before death. No mortalities were observed after exposure
of either char or sturgeon for 96 h at measured concentrations as
high as 14.2 μg/L. This is the first study to demonstrate the
acute toxicity of 6PPD-quinone to other fishes of commercial, cultural,
and ecological importance at environmentally relevant concentrations
and provides urgently needed information for environmental risk assessments
of this contaminant of emerging concern.
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