6PPD Update – January 2026

Communications and Outreach

Ecology’s current work to address 6PPD and 6PPD-quinone (6PPDQ) is highlighted below. This update includes current agency actions. Contact us at 6PPD@ecy.wa.gov.

Momentum Builds for Solutions to Tire Wear Pollution: Last month, Ecology hosted a virtual 6PPD State of the Science Forum, connecting researchers, policy practitioners, and partners from across the globe to share knowledge and accelerate progress.

More than 400 participants joined live via YouTube and Zoom to explore innovative solutions, connect across disciplines, and strengthen collaborations focused on reducing the impacts of 6PPD and 6PPDQ.Over the two-day forum, 33 presenters shared insights on topics including mapping and monitoring, human health toxicity, stormwater management, and safer chemical alternatives. The event highlighted growing momentum to find solutions through collaborative science and informed policy.Recordings and related resources are available online.

Finding a Solution

Ecology is focused on several key areas to reduce the threat of 6PPDQ on aquatic life. We highlight our efforts to advance research and activities below.

Assessing 6PPDQ risk to aquatic life: measuring and mapping to support recovery

Contact: Rhea Smith, 6PPDQ Integrated Watershed Assessment Lead

Monitoring, Methods, and New 6PPDQ Studies: The 6PPDQ inter-agency sampling team successfully retrieved the fall 2025 passive samplers ahead of extensive flooding. Samples are now being analyzed at Ecology’s Manchester Environmental Lab. We will share our methods and findings in an upcoming 6PPDQ Hotspots in Urban Watersheds progress report.

We also recently completed an urban watershed study using stream sampling telemetry stations to capture peak 6PPDQ concentrations during storm events, improving our understanding of its fate and transport.

Photo: U.S. Geological Survey and Ecology staff deploying a sampler in a salmon stream at Gorst Creek on the Kitsap Peninsula, as part of a collaborative spatial sampling survey conducted in fall 2025.

We are launching a new National Estuary Program-funded study with the Washington Department of Fish and Wildlife and Washington State University to explore whether amphibians are sensitive or tolerant to 6PPDQ exposure. In addition, we are partnering with the U.S. Geological Survey to further evaluate the use of passive samplers for stormwater conveyance research.

Reducing sources of 6PPD: tire research, alternatives assessment, and action plan

Contact: Tanya Williams, 6PPD Lead Agency Planner

USGS Evaluates Toxicity of 6PPD and Potential 6PPD Alternatives: 

Researchers at the USGS Western Fisheries Research Center evaluated the toxicity of 6PPD, several potential alternatives, their quinones, and ozonated transformation products. Toxicity was assessed in-vitro using cell lines from coho salmon, Chinook salmon, and rainbow trout.

Results in the Toxicity of 6PPD Alternatives to Salmonid Cell Lines report showed that ozonated 7PPD and IPPD exhibited toxicity similar to 6PPD in coho and rainbow trout cells. In contrast, CCPD and 77PD did not show measurable toxicity in-vitro.

Figure 4 from the report (right) summarizes EC20 concentrations for each chemical tested. Concentrations represent the parent compound, quinone concentrations for quinone, and ozonated transformation mixtures. The x-axis is presented on a log10 scale. “N/A” indicates no detectable alteration in metabolic function at the maximum concentration tested; therefore, no EC20 was calculated.

*Figure 4: CHSE – Chinook salmon, CSE – coho salmon, RTG – rainbow trout

Reducing 6PPDQ in stormwater: mitigation and best management practices

Contact: Shelby Giltner, 6PPD Environmental Engineer

Collaborative Research Advances Stormwater BMP Effectiveness: Ecology’s Water Quality program is finalizing contracts for BMP Effectiveness Studies, including amendments that extend and expand work from the previous biennium. Several projects are already underway, with a focus on stormwater treatment systems, street sweeping effectiveness, bioretention systems, and other research related to the fate and transport of 6PPDQ. This work is in collaboration with multiple partners, including the City of Spokane, Washington Stormwater Center, Snoqualmie Indian Tribe, King County, and contractors NV5, and EA consultants.

In addition, Ecology is negotiating new contracts, including a USGS grant to develop and evaluate stormwater infrastructure monitoring methods, monitor stormwater catchments on arterial streets, and synthesize BMP effectiveness research and guidance related to 6PPD in stormwater.

Working Groups

Stormwater Work Group (SWG) (Julian Carroll): The SWG has an upcoming virtual meeting on Feb. 11, 2026 from 9 a.m. to 12 p.m. We will also begin creating a new Charter and 2026-2027 Work Plan during the first meeting of the new Charter and Work Plan Subgroup in late February.

Stormwater Work Group 6PPD Subgroup (Shelby Giltner): The SWG 6PPD Subgroup held a meeting on Dec. 4, 2025. Ecology provided updates on current 6PPD research projects. In addition, David Burger with Stewardship Partners and Dylan Ahearn, PhD with Herrera presented on Adopt-a-Downspout – Stewardship Partners project. Meeting notes and presentation slides are available online. The next SWG 6PPD subgroup meeting is Feb. 19 from 10 a.m. to 12 p.m. Download the outlook calendar invite.

Upcoming 6PPD Meetings and Events

Resources & Research

6PPD and 6PPDQ research is underway around the world. Below are links to recently published papers and other resources that inform Ecology’s work.

Additional Resources

Ecology is working to address 6PPD through source reduction, stormwater management, and environmental monitoring. You can sign up to receive future updates and read more about our 6PPD work below.