December 7, 2020

Cars killing Salmon in Seattle’s Puget Sound Creeks

While there is lots of discussion about electric vehicles as solving emission issues,there are other outstanding problems with automotive use that needs to be evaluated and considered.

I have already written about vanadium, the metal particles in the dust from worn-out brake pads on vehicles being just as harmful as diesel emissions. Called BAD for Brake Dust Abrasion, studies done by King’s College London found that the metallic  dust from brake pads cause lung inflammation and “reduce immunity, increasing the risk of respiratory infections.”

As reported in the BBC the head researcher Dr. Liza Selley found that 55% of traffic pollution is from non-exhaust particles, and 20% of that is brake dust. The dust is caused by the friction of the brake rotor grinding on the brake pads when a vehicle is braked, and the dust becomes airborne. Her research shows that the impact of this dust is just as severe as that of diesel particles. You can read Dr. Selley’s complete study here.

In Seattle’s Puget Sound, the City has been restoring creek beds for salmon, and coho or silver salmon have come back. But in any inclement weather the coho salmon have suffered huge die-offs, with no one able to figure out what was killing them.

Scientist researchers at the University of Washington Jen McIntyre, Edward Kolodziej and Zhenyu Tian have isolated the poisoned chemical that is killing the salmon only to find out it is a little known chemical that is part of a car tire preservative.As the Los Angeles Times writer Angela Xia found out, the chemical is part of a “soup of pollutants, which includes trillions of microplastics, rushes down drains and into creeks and ultimately into the sea.”

Just from the act of driving vehicles on roads, tire degradation means particles end up in storm water flowing off roads. The toxic chemical is lethal to large fish, and is is probably found on every heavily used road globally.

This has profound implications to Coho stocks which have been depleted along the California coast.

It may also provide a reason for the failure of the four streams in San Francisco Bay that used to have coho. Of course the next question is whether roads and highways that cross freshwater have been responsible for the extinction of Coho along the coast.

A salmon expert and emeritus professor at University of California Davis Peter Moyle states ”

The challenge when you talk about declines of really sensitive fish like coho salmon, is that there are so many things that are affecting them simultaneously, it’s hard to pinpoint one.That’s why it’s so interesting that in these Puget Sound streams, they found this one chemical that seems to be the smoking gun.”

Besides studying dozens of streams and fish kills to assess that stormwater from busier roads was the culprit, the researchers also looked at tires. By immersing tire particles in room temperature water they identified and isolated 1,500 to 2,800 leaching chemicals, and then analysed them.

They then figured out which chemicals were poisonous to salmon, narrowing it down to 6PPD  which is tire preservative developed to slow tire breakdown. Combined with ozone gas on the road, it develops into a toxic compound.

This work has been proceeding for fifteen years and contributes to the growing realization that vehicles themselves are contributing to a growing pollution problem. The researchers also discovered that of all the microplastics in Puget Sound, the majority were tire particles.

Joe Dillon, a water quality and toxicology specialist  with the National Oceanic and Atmospheric Administration says the next step is to figure out who and how will stop the use of this compound in tire manufacture.

“Now that they’ve gotten it nailed down to one compound — that’s amazing. It’s also really helpful that something could be done about it,This means the tire industry can work on figuring out how to replace that compound with something less toxic. It means they can be pushed by the state of California or by nongovernmental organizations to undertake that work.”

The YouTube video below describes the work undertaken by University of Washington researchers Jen McIntyre, Edward Kolodziej and Zhenyu Tian. Their study is available to read here.

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