Each fall, more than half of the Puget Sound coho salmon die before they can spawn. Researchers have found the answer to this question: when it rains, stormwater flushes the remnants of aging car tires from the roads into nearby bodies of water. This waste contains a deadly mixture of chemicals, particularly a molecule associated with a preservative that prevents tires from deteriorating too quickly.
Most people think that we know exactly which chemicals are toxic, and all we have to do is control the amount of these chemicals so that we don’t pollute water bodies. However, what happens is that animals are influenced by a huge number of factors that we do not even know about.
Edward Kolodziej, Associate Professor in the UW Tacoma Division of Science and Mathematics and the UW Department of Civil and Environmental Engineering.
Tire scraps contain a mixture of 2,000 chemicals: this “chemical killer” is probably found on every road in the world.
Coho salmon is born in freshwater streams and spends about a year there. The fish then move to the sea, where they spend most of their adult life. Approximately 0.1% of individuals return to their original habitat or shallow bodies of water to lay eggs. However, researchers began to notice that the returning fish died before they could spawn, especially after heavy rain.
Research has shown that a solution made from used tire particles is highly toxic to salmon. After the composition was studied in detail, it was revealed that 6PPD, a chemical used to prevent tires from breaking down too quickly, was deadly to fish.
Now scientists have to find out how other fish react to this chemical, who are more or less sensitive to it.