Tires and toxics (6PPDQ)

A tire-related chemical found to kill coho salmon and other fish has come under intense worldwide investigation ever since Puget Sound researchers isolated the singular compound from among thousands of pollutants residing in stormwater. The chemical, 6PPD-quinone (6PPDQ), was virtually unknown until its isolation in 2020. Now, it is recognized as one of the most toxic chemicals ever seen in the aquatic environment. Scientists from at least 10 countries have been measuring its effects on a variety of fish and other organisms. Meanwhile, other researchers have been probing the chemical’s influence and damage at the cellular level. In rapid succession, dozens of reports in scientific journals have described some remarkable findings — and yet much about 6PPD-Q remains unexplained.

Source: Encyclopedia of Puget Sound

Overview

Environmental engineers and chemists at the University of Washington Tacoma have identified a mysterious compound implicated in the deaths of large numbers of coho salmon in Puget Sound. The chemical is linked with a rubber additive commonly used in tires and is thought to kill more than half of the spawning coho that enter the region's urban streams every year. 

A returning Coho Salmon at the Suquamish Tribe's Grovers Creek Hatchery. Photos: K. King/USFWS (CC BY-NC 2.0)

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Modern automobile tires are a complex mixture of chemicals, all used together in different ways to give tires their structure and properties, including riding comfort, safety and long life. Chemicals from tire wear particles are now thought to be responsible for the deaths of large numbers of coho salmon returning to spawn in Puget Sound streams. 

Researchers are trying to determine which chemicals in stormwater are contributing to the deaths of large numbers of coho salmon in Puget Sound. It has prompted a larger question: What exactly is in stormwater, anyway?