Fish living downstream of storm drains are exposed to contaminants in the runoff every time it rains, including the tire-derived chemical 6PPD-quinone. This drug has recently been connected to catastrophic coho salmon die-offs on the West Coast of the United States. Researchers report in the American Chemical Society’s Environmental Science & Technology Letters that exposure to 6PPD-quinone at ecologically relevant levels may kill rainbow and brook trout, but not Arctic char or white sturgeon.
Protectants, such as N-(1,3-dimethylbutyl)-N’-phenyl-p-phenylenediamine, or simply 6PPD, are added to rubber tires so that they may be driven safely for a long period. Small rubber particles disperse over highways when the treads wear down and portions break off over time. They react with oxidants in the air, like as ozone, to convert 6PPD to 6PPD-quinone, which then washes into rivers with the source tire particles in stormwater runoff. Previous research has shown that modest levels of 6PPD-quinone are harmful to coho salmon, a popular recreational fish and an ecologically significant species, and are likely to be the origin of the condition known as urban runoff mortality syndrome in urban streams. In contrast, another research found that zebrafish and Japanese medaka can tolerate even large doses of 6PPD-quinone. As a result, Markus Brinkmann, Markus Hecker, Steve Wiseman, and colleagues sought to discover whether this pollutant is harmful to a wider spectrum of economically, culturally, and ecologically significant fish species.
The researchers used different doses of 6PPD-quinone on young brook trout, rainbow trout, Arctic char, and white sturgeon. Even low quantities, such as those observed in surface waters during stormwater overflow events, were proven to be deadly to brook and rainbow trout. The researchers noticed a rise in blood glucose levels in both trout species following exposure to 6PPD-quinone, suggesting that it impacted the fish’s energy metabolic pathways. After four days of exposure to a high level of the pollutant, equivalent to the greatest quantity previously reported in stormwater runoff, none of the Arctic char and white sturgeon perished. The findings show that mortality from exposure to 6PPD-quinone differs by fish species, although non-lethal effects may be present in individuals that do not die, according to the researchers.
A financial gift from Fisheries and Oceans Canada helped to fund this investigation in part. The authors acknowledge additional funding from the Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grants program, Western Economic Diversification Canada (WED), the Canadian Foundation for Innovation, NSERC’s Banting Postdoctoral Fellowship program, CFREF, and the Canada Research Chairs Program.