Last October, volunteers with the West Vancouver Streamkeeper Society noticed dozens of coho salmon floating dead in Brothers Creek. The carcasses were intact, and looking healthy. They had not yet spawned.

Until a few years ago, mystery coho die-offs similar to this were known only as “urban stream syndrome.” In the urban areas of the Pacific Northwest United States, 40 to 90 per cent of coho returning to spawn were succumbing. The deaths had become so ubiquitous that they posed a threat to salmonid conservation across 40 per cent of the Puget Sound area.

“When you have a loss like this, it’s devastating,” John Barker, a volunteer for the West Vancouver Streamkeeper Society, told CBC News last fall when the Brothers Creek incident took place.

Coho die-offs drew the attention of a group of more than two dozen scientists, led by researchers at the University of Washington and Washington State University Puyallup. Knowing the incidents were somehow linked to storm events and runoff into streams, the team followed a toxin trail from roadways to streams and ultimately to a compound called 6PPD-quinone. 6PPD is added to tire rubber to prolong the life of tires. When it is exposed to air it turns into 6PPD-quinone. Even one microgram of 6PPD-q per litre of water is acutely toxic.

6PPD in tires is converted to 6PPD-quinone when exposed to ozone. 6PPD-q is contained in tire
wear particles that can be transported to surface waters through stormwater drains and runoff. then ingested and absorbed by fishes. Credit: Hannah Vinyard, Washington State Department of Ecology, courtesy of the U.S. Interstate Technology and Regulatory Council.

Coho didn’t stand a chance, and it’s not just coho. Other fish are also affected by the toxin.

“Most people think that we know what chemicals are toxic and all we have to do is control the amount of those chemicals to make sure water quality is fine. But, in fact, animals are exposed to this giant chemical soup and we don’t know what many of the chemicals in it even are,” Edward Kolodziej, an associate professor in both the UW Tacoma Division of Sciences and Mathematics and the UW Department of Civil & Environmental Engineering and co-senior author of the study, told the UW News when the study was published. “Here we started with a mix of 2,000 chemicals and were able to get all the way down to this one highly toxic chemical, something that kills large fish quickly and we think is probably found on every single busy road in the world.”

Their study was published in the peer-reviewed journal Science on December 30, 2020. And… crickets in Canada.

In the U.S., the Yurok, Port Gamble S’Klallam, and Puyallup Tribes petitioned the U.S. Environmental Protection Agency to prohibit the use of the chemical compound in tires. Last November, the EPA agreed. The agency is now assessing potential regulations.

“Available information on 6PPD-quinone indicates that it is toxic enough to quickly kill some fish,” says the agency. “Concentrations in stormwater were found to be lethal for coho salmon following exposures lasting only a few hours.”

In Canada, Watershed Watch and allies Raincoast Conservation Foundation and the Pacific Salmon Foundation, with the help of Ecojustice, have formally requested the federal minister of environment and climate change order an assessment of 6PPD and 6PPD-quinone. We are waiting for the minister to respond to our letter.

In late March, an international consortium of tire manufacturers announced they have identified five potential alternatives to 6PPD that will be further studied.

It is estimated that around 1,900 tons of 6PPD-q is released into the environment from tire wear every year in the U.S. alone and it’s been documented in road runoff and wastewater at levels of concern in Toronto and Saskatoon, and now in B.C.

“The science is clear: 6PPD-q is responsible for mass deaths of coho salmon as they pass through urban areas. More research is still needed to determine whether 6PPD-q is toxic to other salmonids, aquatic species, and our ecosystems at large. It’s time for Canada to take steps towards regulating 6PPD in Canada and protect wild salmon,” says Daniel Cheater, a lawyer with Ecojustice.

“With emerging research showing us the direct impacts of tire wear and tear on salmon and other fish species, it is our responsibility to hold regulators to a higher standard and demand the source of the problem be tackled,” says Lina Azeez, Habitat Programs Director at Watershed Watch. “Everything is connected. Urban runoff and pollution impact salmon, which in turn impacts the very building blocks of our ecosystem.”