Salmon was dying and no one knew why.
About 20 years ago, ambitious restoration projects brought Koho Somlmon back to Urban Creek in the Seattle area. But after it rains, the fish will show strange behavior: one side listed, rolling, swimming in circles. They die in a few hours – before they are born, taking the next generation with them. In some streams, up to 90% of the coho salmon was lost.
“It was amazing to take part in this sick fish,” said Jennifer McIntyre, now a toxicologist and professor at Washington State University who is part of a team that, years later, has uncovered the mystery of Salmon who died around Puget Sound. . “In those early years, we had intense discussions. What could be the reason for this?”
The team’s findings were published Thursday in the journal Science.
The investigation began with a forensic examination. Was it metal or some other chemical in the water? They found nothing. Problems with temperature? No. Maybe lack of oxygen? Salmon seemed to be suffocating, but he had plenty to breathe. No evidence of disease or pesticide exposure was found. But due to the connection with the rains and the lack of any other explanation, Dr. M. Contire and his team focused on the work that was going on off the roads.
In partnership with a local fish hatchery run by the Sukwamish tribe, they decided to test the principle, in which they would expose fish to a mixture of chemicals made from chemicals, such as heavy metals and hydrocarbons from motor oil. But even at surprisingly high concentrations the salmon was not affected.
The scientists decided to try again with the real stuff, the real runoff. Luckily for them, the parking lot at the Northwest Fisheries Science Center, downhill from Elevated Road, became vacant, where some of the team members were working. On a rainy day in 2012, they filled a stainless steel container with a liquid filled with translucent dark liquid. At this point, Salmon exhibited strange symptoms and died instantly.
“What’s in that mix?” Dr. Mc. “This is the water that’s on the road, that’s what we wrap in our rain boots.” It should be something that people don’t measure regularly, she said.
Edward P., an environmental engineer and chemist at the University of Washington. Enter Kolodziz. His laboratory used a machine called a high-resolution mass spectrometer to compare the chemical composition of the highway ref off funnel, with water collected from two urban bays where the salmon was dying. Samples are divided into chemicals related to tire particles. So the team soaked the cut tires in water to reassure them of an exam. Salmon died.
They were getting closer to the answer, but the tire water still had more than 2 thousand chemicals in it. To solve the mystery, they had to identify the specific culprit. Dr. Kolodziej and other researchers narrowed the field by isolating the tire solution into different chemical compounds, and then testing it on fish. With a van diagram type approach, they got their list of up to 200 chemicals. Whenever they were known to be toxic to fish in the literature, they bought it and tried that individual chemical.
“We’re almost going to bet in the lab whether we think the chemical thinks it will kill the fish.” Dr. Kolodziz said. “And he never did.” Flame is not a deterrent. No plasticizers. Not a bunch of other people you’ve never heard of.
“We were stuck,” said research scientist Zhenyu Tian, who did a lot of analysis.
“Frustration,” said Dr. Kol.
Then the Ph.D. Student, Haoki Nina Zhao suggested a new way of isolating chemicals that became the main suspect. But they couldn’t verify it, because they didn’t know what it was.
“It’s almost like you have a fingerprint,” DT said. “But you don’t really know who it is, because in your database, this fingerprint doesn’t exist.”
Dr. Tian’s “Aha!” The moment came one morning. Assuming that the secret chemical origin has changed from a substance added to the tire, he discovered a compound whose carbon and nitrogen atoms ignore oxygen and hydrogen, as the latter is more likely to change when the chemical changes. In the Environmental Protection Agency’s report on tire rubber, they found a match: an anti-corrosive called 6PPD.
The researchers ordered as little as one pound of purple pills as they could afford. When they oxidized this substance, the resulting chemical felt like they had worked so hard to separate from the tire water. It was time to test this version, 6 ppd-quinone, on the version.
Dr. “I’m really sad to see the fish die,” Kolodzi said. “You’re just watching this fish struggle. And yet you are happy to understand why. ”
The killer had 6 ppd-quinone from the tire in the run run of the road.
“Their analysis is really surprising,” said Nancy Denslow, professor and director of aquatic toxicology at the University of Florida, who was not involved in the study. He also praised a large number of writers. “It’s wonderful to see large groups of people coming together to solve problems,” he said. “Group science is fantastic.”
His answer raises a number of questions, however.
She has done further research on how the runoff affects some other species of fish (almost not dramatically, but there are still results). The team is in talks with the tire industry and hopes manufacturers will prepare to find a replacement preservative. Scientists are concerned about the widespread health effects of chemicals in tires, including humans, especially as tires are frequently recycled to create artificial turf for sports fields. “It makes me think it can be an inhalation of excellent particles,” Dr. Mc. Said Mc Kinter. “Now you have found that this type of leaching occurs on the lung tissue.”
While chemicals always surround us (plants themselves are chemical factories), over the last hundred years, humans have been making them artificially. Dr. “We’re synthesizing them faster than we can sustain them,” Kolodziz said.
“I think most of them are OK, but there are bad actor chemicals floating around there,” he said. “And it’s a long, slow and difficult process to identify them.”
