Urban rivers, like the Spokane River face many challenges from various pollutants, one of which is a relatively new and concerning chemical: 6PPD-quinone.
What is 6PPD/6PPD-quinone?
6PPD isa preservative used in every single tire. When it breaks down, if forms the toxic chemical 6PPD-quinone. Tire manufacturers use 6PPD to protect tires from ozone degradation and extend their lifespan. However, as tires wear down, tiny particles containing 6PPD shed onto roads. Runoff and rainfall wash these particles into storm drains and eventually into rivers, where 6PPD reacts with ozone in the water to form 6PPD-quinone.
Although we have limited information about 6PPD’s impacts on human health, scientists have observed the devastating effects of 6PPD-quinone on salmon. Even in small concentrations, 6PPD-quinone proves lethal to aquatic life, particularly coho salmon, rainbow trout, and other salmonid species.
This raises significant concerns for regions like ours, where salmon and other native fish play a critical role in the ecosystem and hold cultural and economic importance. 6PPD-quinone’s impact on fish populations directly reduces access to healthy foods for people who rely on fish for subsistence, especially local Native American tribal members that consume salmon as a traditional food source and other fishermen who fish to sustain their families.
Why is the Spokane River Vulnerable?
The Spokane River is particularly vulnerable to contamination from 6PPD-quinone for several reasons:
Urban Runoff: The Spokane River flows through urban areas filled roads, highways, and parking lots. These surfaces collect tire wear particles, which are then washed into the river during rainstorms. The more urbanized an area, the greater the potential for 6PPD contamination.
Stormwater Management Challenges: Many stormwater systems fail to filter out small particles like tire dust, allowing contaminated runoff to flow directly into the river during heavy rains. But, once removed and mitigated, the damage from 6PPD stops, unlike ‘forever chemicals’ that persist in the environment. This means stormwater management is key in addressing the problem.
Salmon Habitat: The Spokane River provides a home to several fish species, including redband trout, which face heightened risks from 6PPD-quinone. The chemical’s ability to cause sudden death in coho salmon raises concerns about its impact on other species in the river, including hatchery salmon released to spawn in the fall.
Moves to Regulate 6PPD
Both the federal and state governments have taken steps toward regulating tire manufacturing and restricting 6PPD discharge in stormwater, but regulations remain insufficient to fully protect native fish populations. Regulation of 6PPD must address the contamination already present in the environment through stormwater management and prevent further contamination by regulating the use of 6PPD in manufacturing.
Following a petition by EarthJustice, EPA agreed to draft federal regulation to restrict 6PPD in tires, but those regulations are still in draft form. In addition, the EPA has released draft aquatic life criteria screening values for 6PPD and 6PPD-quinone of 11 nanograms/L (0.011 micrograms/liter). Although these screening values provide guidance for local governments to monitor and protect aquatic organisms from 6PPD-quinone, they do not impose legally binding requirements.
Washington State’s Department of Ecology has proposed 6PPD-q freshwater quality discharge limits of 0.008 micrograms/liter. Final passage of this rule would require municipalities and industrial discharges with stormwater permits to monitor for and treat their runoff for 6PPD and 6PPD-quinone. But this requirement will only apply as the current permits expire and get updated to be consistent with this new rule.
The largest stormwater permit for the Spokane River is the Eastern Washington Phase II Municipal Stormwater Permit, took effect August 1, 2024 and will remain in effect until 2029. The permit requires 25 entities, including the City of Spokane, Spokane Valley, and Spokane County, to manage and control stormwater runoff so that it does not pollute downstream waters. Most of the 6PPD and 6PPD-quinone in our watershed likely comes from sources covered by this permit.
Regulation in the U.S. continues to lag behind what’s necessary to control contamination from 6PPD-quinone. Globally, the situation is different. The European Chemicals Agency has categorized 6PPD as a category 1B reproductive toxicant due to evidence of increased accumulation in pregnant women, highlighting the need for large-scale protective measures to safeguard both human and aquatic health.
You Can Help
Your voice can help protect our waterways from toxic pollution. We’re joining the Waterkeeper Alliance and other Waterkeepers across the nation to urge Congress to fund research into safer alternatives and create a path to phase out 6PPD. Please contact your representatives today and ask them to prioritize clean, healthy rivers for all.