Compound Stemming from Tires Toxic to Several Species of Fish

Rubber tires generally contain protectants such as the antioxidant N-(1,3-dimethylbutyl)-N‘-phenyl-p-phenylenediamine (6PPD). However, as the tires wear down, small rubber particles are left in the environment. There, they react with oxidants such as ozone in the air, and 6PPD is converted to 6PPD-quinone. This derivative washes into waterways along with the tire particles in stormwater runoff. Fish living downstream of storm drains are exposed to these pollutants. Recently, 6PPD-quinone has been linked to massive die-offs of coho salmon across the U.S. West Coast—a popular fish among recreational fishers and an environmentally important species. Other fish species can withstand even very high amounts of 6PPD-quinone.

Markus Hecker, University of Saskatchewan, Saskatoon, Canada, and colleagues have investigated whether this contaminant poses a risk to a broader range of commercially, culturally, and ecologically important fish species. The researchers exposed juvenile brook trout, rainbow trout, Arctic char, and white sturgeon to varying levels of 6PPD-quinone. The team found that exposure to 6PPD-quinone at environmentally relevant levels can be deadly for rainbow and brook trout, though not for Arctic char or white sturgeon.

The researchers observed that even small concentrations, such as those regularly occurring in surface waters after stormwater runoff events, were fatal to brook and rainbow trout. For both trout species, the researchers observed increased blood glucose levels after 6PPD-quinone exposure, suggesting the compounds affects the fishes’ metabolism. In contrast, none of the Arctic char and white sturgeon died after four days of exposure to a high level of the contaminant, similar to the maximum amount previously observed in stormwater runoff.

The results indicate that the mortality from exposure to 6PPD-quinone varies among fish species. However, for animals that do not die, possible non-lethal effects cannot be excluded and might need further examination.