Our tires shed toxins that kill fish. Here’s a partial fix

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1. >The most concerning of these chemicals is 6PPD. Developed in the 60’s and used widely in tires since the 1970’s, 6PPD was first made as a tire preservative, but it has a deadly unintended byproduct: as it protects our tires, it produces a compound lethal to coho salmon called 6PPD-quinone. For more than 50 years, tires have shed tiny toxic particles that are carried in dust through the air and washed by rainwater into streams, killing fish in urban habitats. It is so potent it is now colloquially known as the tire wear toxin.
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   >What if, thought post-doctoral fellow Timothy Rodgers, rainfall could pass through rain gardens that would act like a Brita filter before hitting urban streams?
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   >Under the guidance of Rachel Scholes, assistant professor of environmental systems engineering out of the University of British Columbia, Rodgers started to plan.
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   >Rain gardens work by using soil as a filter. When water is filtered through the system, the chemical is almost entirely absorbed into the ground before it can enter streams. In soil, 6PPD-quinone breaks down over time. This makes rain gardens an effective way to mitigate the introduction of the chemical into urban coho spawning habitats.
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   >“What we have to do is prevent it from getting into these urban streams in the first place,” Krogh said.
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   >“Whatever we’re going to do, we have to use cheap and readily available materials because there’s so many different roads and river crossings that we can’t afford expensive solutions here.”
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   >The 6PPD chemical helps tires last for approximately 100,000 km for the average consumer, says Rodgers — substantially longer than the 1,000 km they would without it.
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   >Work is underway to find replacement chemicals for tires in the U.S., but possible solutions, including other PPD variants are not perfect, Rodgers says. Even if one is found, the average consumer keeps their tire for five years, he adds, so it would take years before tires containing the chemical are circulated off roads.
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   >“Have safer alternatives popped up? Yes. Do they look promising? Maybe,” Rodgers said.
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   >“You could probably just replace [6PPD] with another PPD in the short term… but I still think that in the long term that would be a mistake because these compounds still have fairly high aquatic toxicity, [and] they still have fairly high human toxicity.”
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   >In the interim, mitigation is critical to manage the chemical, which claims the lives of an estimated 40 to 90 per cent of coho in urban watersheds each year. The chemical has sparked lawsuits in the U.S. and mass calls from environmental groups to enact regulatory action.
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   >The chemical’s harms were first discovered in 2020 by Edward Kolodziej’s team out of the University of Washington. In the past four years, research has been conducted to better understand what the chemical is doing not only to coho salmon habitats, but human health as well.

   Clearly the best solution is to reduce the amount of driving that people need to do so that we can reduce the wear on tires more broadly. Aside from that, as the article mentions, mitigation would be a good initial solution, followed by changing the kinds of chemicals used with the usual caveats.