FFor decades, coho salmon returning from the Pacific Ocean to the creeks and creeks of Puget Sound in Washington state to spawn were dying in large numbers. Nobody knew why. Scientists working to solve the mystery of the mass deaths noted that they occurred after heavy rains.
Toxicologists suspected pesticides, as the main stream they studied ran through a golf course. But no evidence of pesticides was found. They ruled out diseases, lack of oxygen and chemicals such as metals and hydrocarbons.
The first real breakthrough occurred when they tested real runoff collected from a nearby road and exposed test salmon to it. The fish died within hours.
“The hardest step was digging into what might be in that stormwater,” said Jenifer McIntyre, an assistant professor of aquatic toxicology at Washington State University who spent 15 years looking for what was killing coho, an important species in the world. North Pacific. -West.
it was when they car tire particles tested – a little-known but ubiquitous contaminant – that they knew they were on the right track. Using a Parmesan cheese grater on top of a drill, they carefully cut up small pieces of tire and soaked them in water.
“When we tested the tires, they killed all the fish,” McIntyre said. From there, they were able to pinpoint the culprit: a toxic chemical known as 6PPD-quinone, a product of the preservative 6PPD, which is added to tires to prevent them from breaking down. the pioneer to studypublished in 2020, has been heralded as fundamental to our understanding of what some describe as a “stealth contaminant”.
Environmental scientists consider tire wear particles, a mixture of tire debris including synthetic rubbers, fillers and softeners, and road surface particles, to be one of the most important sources of microplastics in the ocean.
Created during acceleration and braking, they are dispersed from road surfaces by rain and wind. The main environmental pathway runs from road runoff to storm drains, where it empties into rivers and the sea. They are also released from sewage effluents and the atmosphere, where they can circulate to the ocean and back. A 2020 study suggested windblown microplastics they are an even greater source of ocean pollution than rivers.
While it’s fiendishly difficult to pin down the exact composition of microplastics, there’s plenty of research to suggest that tire dust makes up a significant part.
In 2017, a world model by the International Union for Conservation of Nature estimated that tire wear is the second largest source of primary microplastics in the ocean, at 28%, after synthetic textile fibers, at 35%.
And, in 2019, a report by scientists across Europe concluded that car tire abrasion was a major source of microplastics and possibly nanoplastics. While there is still a lack of data on risks to the environment and Human healthThe scientists concluded that if future emissions remain constant or increase, “ecological risks could be widespread within a century.”
One thing is certain. Tire wear particles are ubiquitous. The average tire lose 4kg throughout his life. On 6 million tons of tire particles are emitted annually and have been found everywhere, from the deep sea to the atmosphere, even in the Arctic and Antarctica.
And it’s only going to get worse. Electric cars will reduce tailpipe emissions, but tire wear is projected to increase, due to heavier vehicles and torque (the rotational force of a car’s engine). The UK air quality group warned in 2019 that dust from car tires and brakes keep polluting the airrivers and ultimately the sea, even as the fleet has gone electric.
In January, McIntyre’s research team published a new to studywhich found that 6PPD-quinone was “more toxic than previously estimated” to coho and should be classified as a “very highly toxic” contaminant to aquatic organisms.
Like any detective, McIntyre hopes his team’s work will prompt others to look back at locally extinct aquatic species to determine whether 6PPD-quinone may have played a role.
Dr. Steve Allen, an atmospheric microplastics specialist at Dalhousie University’s Ocean Frontier Institute in Canada, described the coho salmon study as “landmark” because it examined the real-world effects of tire particles.
The study of microplastics is advancing rapidly, but it is still in its infancy. Fewer than 100 scientific papers have been published on them to date, Allen said, all of them in the last decade.
siobhan anderson, The co-founder and chief scientific officer of the Tire Collective, a group of master’s students that designed a device to collect microplastics directly from tires, calls tire dust “a stealthy pollutant” because few people know it. “There is very little public awareness,” said Anderson, whose organization is in talks with Volvo and Seft about developing the device for him.
“Tire wear is unique in that it can count as microplastic, but it’s also air pollution because it’s so small,” he said. “Anything that is 10 microns can be inhaled into our lungs and anything that is 2.5 microns has the potential to cross the membrane barrier,” Anderson said.
Tire dust particles found be smaller than 23 nanometers (0.02 microns).
Edward Kolodziej, associate professor at the University of Washington and co-author of the coho study, cites two studies from China showing that tire dust is a major contributor to urban air pollution. “It’s not just road runoff and stormwater that gets into the river that kills fish, there are also unknown or poorly characterized chemicals present in these things that end up in our lungs.”
Kolodziej is concerned about the huge data gaps in our knowledge of the effects of thousands of chemicals in the environment. “As a society, we are literally manufacturing 300,000 chemicals, of which 20,000 to 30,000 are the most used,” he said. “Between 90% and 95% of chemicals they have not had an evaluation of what they do in the environment.”
“All of these chemicals are proprietary and confidential business information. When you go and buy a product like a tire, no one is told what chemicals it contains.”
Frédérique Mongodin, senior marine litter policy officer for Seas At Risk, said she is very concerned about the “chemical cocktail” of tires. “Tire dust is impossible to control. We are pressing the EU to introduce measures at the design stage.”
the $264bn (£194bn) a year The tire industry is countering scientific studies on tire wear and microplastics with research of its own.
The Tire Industry Project (TIP), a body representing 10 tire manufacturers including Goodyear, Michelin and Pirelli, has commissioned multiple studies over the last decade, concluding that TRWP (road and tire wear particles) do not present environmental or health risks.
Gavin Whitmore, communications manager for TIP, disagrees that tire wear is a major source of microplastics in the ocean.
“We are finding that a maximum of 2 to 5% of TRWP is reaching the ocean,” he said, citing a two-part study. to study published in 2018, commissioned by the European Association of Tire and Rubber Manufacturerswhich used the Seine basin as a case study.
Environmental groups, however, have questioned the independence of this investigation.
Anne Cécile Rémont, director of the TIP, said that after the coho salmon study, the US Tire Manufacturing Association (USTMA) has been involved in discussions with regulators and stakeholders about “potential alternatives” to 6PPD. . A proposal in california, where the loss of coho salmon has significantly affected indigenous communities, would require tire manufacturers to consider safer alternatives to 6PPD. USTMA has said it supports the proposal.
Asked if the industry was prepared to be more transparent about chemicals in tire wear to speed up investigation, Rémont said the formula is what gives the manufacturer a competitive advantage. “Sharing ingredients is very difficult and complicated,” he said, but added that the USTMA is developing a “substitute test material” for researchers
But experts call for more transparency from tire companies. It took scientists decades to determine what chemical was causing the mass die-off of coho salmon in Washington state.
“Very few people except manufacturers know what’s in tires,” Allen said. “There are thousands and thousands of chemicals. What happens if two of them get together? When it comes to microplastics, we don’t know what a safe level is and we may have already exceeded it.”