All – Edmonds Environmental Council

Following the Flow: Mapping the Road to Cleaner Water

Stories from the people protecting and recovering Puget Sound

July 7, 2026
Written by Sara Bruestle, freelance writer

Salmon are icons in Washington: Their long-distance migrations shape the state’s natural environment and robust economy. Strong salmon runs are vital to healthy ecosystems, the fishing and tourism industries, Tribal treaty rights, food security, cultural heritage, and a way of life.

With 14 salmon and steelhead populations in Washington listed under the Endangered Species Act, their recovery is a statewide investment. Washington is investing billions to restore and protect fish habitat and address threats to salmon.

One of the state’s strategies for salmon recovery is improved stormwater management. Salmon need clean streams, rivers, wetlands, estuaries, and oceans as they migrate hundreds or even thousands of miles during their lifecycles. Despite laws and regulations aimed at protecting water, population growth has contributed to increasing pollution in these waterways.

As cities and towns expand, the number of roads, bridges, and parking lots increases, resulting in more pollutants running into surrounding watersheds. Stormwater runoff can harm fish, limiting their survival rate. One pollutant derived from tires is exceptionally deadly to some salmon.

Gorst Creek

The Gorst Creek watershed on the Kitsap Peninsula is one top-ranked location the Washington State Department of Transportation (WSDOT) is prioritizing in efforts to improve water quality in critical fish habitat. It supports runs of Chinook, coho, and chum salmon, as well as steelhead and cutthroat trout.

The Suquamish Tribe releases 1.8 million salmon into the creek each year. As the salmon leave the Tribe’s rearing ponds, they imprint on the unique odors and geomagnetic fields of the Gorst Creek watershed. This ensures that years later the salmon can migrate back to their home stream to spawn.

The watershed is also home to the notorious Gorst bottleneck, where Highway 3 and Highway 16 merge at the head of Sinclair Inlet. The interchange funnels over 85,000 vehicles daily, as it serves as the main land connection between the Kitsap Peninsula and the rest of Puget Sound.

Traffic heavily backs up during Seattle-Bremerton ferry sailings and Puget Sound Naval Shipyard shift changes. Thousands of cars passing through the narrow corridor get stuck in the Gorst gridlock several times a day.

Chemicals, like those from tires, are released on roads and washed into local bodies of water where they harm salmon and other aquatic life. Credit: iiievgeniy

When it rains, pollution from the traffic washes from Gorst Creek into Sinclair Inlet, including 6PPD-quinone (6PPDQ), a toxic chemical that forms when tires degrade and that researchers identified as fatal to coho salmon in 2020.

For these reasons and more, the Suquamish Tribe and Kitsap County have marked the Gorst Creek watershed as a top priority for stormwater mitigation on WSDOT’s Stormwater Retrofit Prioritization Web Map.

“Sinclair Inlet is a pretty heavily impacted body of water because there’s a lot going on right there in Gorst,” says Joe Rutan, Kitsap County’s county roads engineer. “It’s a highly developed area that is in need of change, and we want to make sure the county is involved in that change.”

Prioritization Map

WSDOT launched the interactive web map in 2024 to pinpoint needs for stormwater retrofit projects that mitigate stormwater impacts from the state transportation system. This collaborative planning tool maps and prioritizes locations along 14,561 miles of state highway for future mitigation.

The state legislature earmarked stormwater retrofits that aid in salmon recovery, ecosystem health, reducing pollution, and addressing health disparities, pledging $500 million in a Move Ahead Washington transportation funding package.

WSDOT surveyed Tribes, towns, cities, counties, and conservation groups, asking them to rank their top priorities for stormwater upgrades. Since the map’s launch, many locations have been top ranked by more than one respondent.

WSDOT’s interactive Stormwater Retrofit Prioritization Web Map shows high priority segments of highway across the state.

“We would like to capitalize on this high level of interest and leverage our investments by accomplishing more than WSDOT could do on its own through partnerships,” says Tatiana Dreisbach, WSDOT’s stormwater retrofit outreach and innovation lead.

The map incorporates perspectives and expertise from across the state to help WSDOT update a transportation system that was primarily built before the Clean Water Act. Through partnerships, those surveyed can steer project plans toward solutions that provide the greatest return on investment – perhaps removing fish barriers or upgrading streambank protection at the same time.

“The WSDOT Stormwater Retrofit Program is working to create and streamline partnership pathways to collectively do more with limited resources, to strategically develop and redevelop the built environment in smart ways,” Dreisbach says.

WSDOT turns to the map when compiling an annual list of standalone stormwater retrofit projects for Move Ahead Washington funding.

Of the 14,561 miles of highway prioritized on the map, 63% are ranked a high priority due to pollution, 30% are ranked a high priority for the salmon population, and 3% are ranked high for existing health disparities. Twelve percent of the highways, or 1,680 miles, score high in all three areas of concern. This includes the Gorst Creek watershed.

Toxic Stormwater

Decades ago, coho salmon traveling upstream through urban waterways to spawn started showing alarming symptoms: They were disoriented, rolling onto their sides, gasping for air, and dying before they could lay their eggs. No one understood why.

For years, scientists tested the water and ruled out typical culprits like heavy metals, disease, high water temperatures, and low oxygen levels. The actual killer was an invisible byproduct of tires.

In 2020, Washington State University and University of Washington researchers linked 6PPDQ to these mass die-offs of coho salmon around Puget Sound over the last 25 years.

Water monitoring data helps Kitsap County meet regulatory requirements and make informed decisions about future water quality improvement projects. Photo courtesy of Kitsap County.

Tire manufacturers use a preservative called 6PPD to prevent rubber from cracking. As tires roll, they shed rubber dust onto roads. When the dust reacts to ozone in the air, the 6PPD transforms into 6PPDQ.

As 6PPDQ is recognized to be one of the most toxic pollutants to fish, there is a widespread urgency to address stormwater impacts. Trace levels – as low as 41 to 95 parts per trillion – are lethal to coho salmon and harmful to other sensitive salmonids, such as steelhead and cutthroat trout. As little as half a drop in an Olympic-sized swimming pool can be lethal. Researchers found that exposed coho salmon experienced mortality rates of 40% to 100%. The fish can die within hours.

In response, the state legislature authorized $500 million over 16 years, starting in 2023, for WSDOT stormwater retrofits as part of its Move Ahead Washington funding package. An additional $15 million was added in 2023 for the legislature’s request, which emphasizes green solutions such as bioswales.

Moving Ahead

WSDOT’s Move Ahead Washington pilot project is on the other side of Puget Sound, 68 miles from Gorst by highway. The Ship Canal Bridge Stormwater Treatment Facility in Seattle will filter polluted runoff from I-5 before it flows into Lake Union.

The project’s scope could treat stormwater from up to 80 acres across multiple jurisdictions, making it WSDOT’s largest standalone stormwater retrofit project to date. It also represents the busiest stretch of highway in the state: Nearly 240,000 vehicles travel across the bridge daily.

“The Ship Canal Bridge has the highest volume of traffic, so it’s some of the dirtiest water coming from the state transportation infrastructure,” Dreisbach says. “This project will be a huge win for water quality and salmon enhancement.”

WSDOT is in the pre-design phase for the project, which includes data collection and community engagement for the planning and development of three design alternatives. Treatment facility construction is expected to begin in 2028.

Over Move Ahead Washington’s 16 years, the state legislature has ambitiously committed to fund $515 million for stormwater retrofit projects. However, recent budget constraints have limited Washington’s ability to provide a steady stream of funding.

WSDOT faces some challenges with the current funding schedule. No funding is allotted between 2027 and 2031, while over $300 million is budgeted between 2035 and 2039. With cash flow issues, the department will be pressed for time and resources to deliver results.

“WSDOT cannot implement a steady stream of stormwater retrofit projects due to funding gaps and pulses, limiting WSDOT’s ability to address urgent stormwater impacts from 6PPDQ and other pollutants in the near term,” Dreisbach says, adding that the hope is that the legislature will optimize the package’s funding schedule.

Kitsap County staff collect information on water quality, stream conditions, and aquatic habitat to identify potential issues, track trends over time, and assess whether stormwater management efforts are effectively protecting streams. Photo courtesy of Kitsap County.

Tribal Interests

Since 2024, 15 federally recognized Tribes have marked 50 locations on WSDOT’s Stormwater Retrofit Prioritization Web Map as top priorities for stormwater mitigation, most of them along state highways encompassing Puget Sound: Ground Zero for 6PPDQ. Tribal rankings are elevated to the top of the list for project scoping. Not only does WSDOT value Tribal rights and interests, but Tribes’ priorities such as water quality and salmon recovery merge with the department’s.

The Suquamish Tribe marked the Gorst Creek watershed as a top priority for stormwater mitigation because it is a 6PPDQ hotspot and the location of salmon restoration work. In addition to its Gorst Creek Rearing Facility, the Tribe operates two Chinook rearing ponds and yearling raceways in the creek. All together, the Tribe’s annual hatchery runs add up to an estimated 2.1 million salmon. While 1.8 million Chinook salmon are released into the creek, another 300,000 coho are transferred to the nearby Agate Passage net pens.

“For more than 40 years, the Suquamish Tribe has operated the Gorst facility to protect and enhance salmon populations,” says Charlie Kratzer, Suquamish Tribe’s hydrologist. “Through a network of hatcheries, rearing facilities and marine net pens the Tribe supports ceremonial, subsistence, and commercial harvests while contributing to the long-term recovery of natural salmon stocks.”

The Suquamish Tribe and Kitsap County hope that the Gorst Creek watershed will make WSDOT’s project shortlist. Kratzer and Rutan agree that the WSDOT Stormwater Retrofit Prioritization Web Map is a useful tool that will help meet the state’s priorities for stormwater management improvements. They’re both interested in partnering on a stormwater retrofit project that will filter contaminants like 6PPDQ from polluted runoff before it reaches streams, helping improve salmon survival.

“How our county roads interact with the state roads and the water is important,” Rutan says. “We need to address that in an environmentally sensitive, caring way.”

Other Ways Washington is Addressing Stormwater Impacts

Washington leads the nation in addressing 6PPD and its toxic derivative, 6PPDQ, following its discovery in 2020. Funding stormwater retrofits that treat the salmon-killing chemical is just one of many strategies in addressing the crisis. In addition:

Tribes petitioned the Environmental Protection Agency (EPA) to establish risk-management rules to restrict or eliminate 6PPD use in tires. The EPA granted the petition in 2023.
In 2024, Washington became the first state to pass legislation regulating 6PPD in tires. It requires manufacturers to report consumer products that contain 6PPD.
The Washington State Department of Ecology (Ecology) is collaborating with manufacturers to find alternate chemical preservatives that could replace 6PPD in tires, and evaluate if those chemicals are actually safer.
Cities are implementing specialized bioretention systems such as rain gardens and engineered soils to filter out 6PPDQ in stormwater runoff, preventing the chemical from washing into waterways. Ecology is also testing new stormwater treatment technologies.
Ecology now oversees statewide water testing in critical streams, wetlands, and estuaries to monitor the presence of 6PPDQ. The data is used to track 6PPDQ hotspots to guide stormwater management and targeted water-quality cleanup projects.
In 2024, Washington was also the first state to establish a numeric water-quality limit for 6PPDQ to regulate contamination. The legal limit is 12 parts per trillion.
During the 2026 state legislative session, the House introduced a bill requiring manufacturers to phase out 6PPD in tires sold in Washington. Although the bill didn’t pass, legislators are likely to propose similar bills in the future.

The Washington State Department of Transportation is implementing Box of Rain, a new stormwater treatment technology, to help prevent stormwater pollutants from reaching salmon-rearing streams. Photo courtesty of WSDOT.

More WSDOT Stormwater Management Partnerships

WSDOT is also working to improve water quality throughout Washington with programs like Box of Rain, Adopt-a-Downspout, and the Roadside Vegetation & Beautification Permit.

Box of Rain is a new stormwater treatment technology developed in partnership with The Nature Conservancy and Stewardship Partners. Like a rain garden in a box, the bioretention system removes pollutants from a bridge’s downspouts before they can enter nearby waterways.

Adopt-a-Downspout is a Stewardship Partners model that asks community volunteers to maintain local Boxes of Rain. For example, the Northwest Fly Anglers have adopted the boxes installed at the Ship Canal Bridge. More volunteer opportunities are in the works.

The new Roadside Vegetation & Beautification Permit expands the scope of an existing permit for WSDOT right-of-way improvements to do more than plant trees and shrubs. It now includes stormwater mitigation to reduce pollutants and control flows. For example, the Duwamish Valley Industrial Greening group applied for the permit to create a stormwater interpretive center in the Georgetown neighborhood of Seattle. The project plans to use the Box of Rain technology to reduce stormwater pollution from an on-ramp to I-5, provide community access to a beautified right-of-way, and install interpretive boards explaining the value of stormwater mitigation.

For more information, view the WSDOT Stormwater Retrofit Prioritization Web Map or visit WSDOT’s Stormwater Retrofit Move Ahead Washington toolbox.

Tire companies race to replace deadly tire chemical

By Christopher Dunagan
Salish Sea Currents Magazine

Published June 05, 2026

The chemical known as 6PPD protects the rubber in tires from degrading by preventing the formation of cracks in the tread and sidewalls. But when 6PPD meets ozone, it transforms into 6PPDQ, a chemical deadly to some species of salmon and trout. Photo: Griffinstorm/Wikimedia (CC BY-SA 4.0)

A chemical found in tires is leading to the deaths of untold numbers of coho salmon in Puget Sound every year. Chemical companies are searching for an alternative but say the unique chemistry and function of 6PPD are major challenges. This article is part one of a three-part series.

In Seattle’s Longfellow Creek, coho salmon are still dying in large numbers before they get a chance to spawn, according to observers. But now a long-term solution to the problem may be inching closer.

Just over five years ago, scientists identified a deadly chemical associated with automobile tires that has been blamed on the untimely deaths of thousands of coho and other vulnerable salmonids. Such losses have been observed not only in Longfellow Creek but in urban streams throughout the Salish Sea. Based on known and suspected toxic levels, salmon may be dying in populated areas from California to Alaska, while numerous trout and char species may be experiencing problems in waterways throughout the world.

Coho salmon in Longfellow Creek are dying before they have a chance to spawn. Photo: AdobeStock

Researchers have been exploring potential alternatives to the tire chemical, known as 6PPD, which blocks destructive ozone before it can attack and destroy the rubber in tires. In the process, 6PPD transforms into 6PPD-quinone (6PPD-Q), one of the most toxic agents known to science.

For nearly 40 years, observers have been watching returning coho become disoriented, keel over and die. Over time, they narrowed the list of suspects — from something in stormwater to automobiles, to tires and finally to a single specific chemical. The effects of 6PPD-Q still reverberate through the aquatic food web, where losses to coho and other populations are immeasurable, experts say.

Although the chemistry of 6PPD has been well known to tire engineers, nobody ever took a serious look at the transformation product, 6PPD-Q, until focused studies examined what was killing coho in Puget Sound. Using advanced techniques, University of Washington researchers with our affiliate the Center for Urban Waters — along with scientists from Washington State University and the National Oceanic and Atmospheric Administration — were able to isolate 6PPD-Q from more than 2,000 compounds found in stormwater.

Now, getting 6PPD out of tires and eventually out of streams has become an all-out goal of numerous tire manufactures, government and nongovernment scientists, as well as agencies responsible for the health of our ecosystems. Outside pressure also is increasing from individuals and organizations concerned about the future of Puget Sound and other waterways.

Alternatives under study

At least a dozen companies and groups associated with the tire industry are working on ways to remove 6PPD from tires. But tire chemistry is complicated, involving 10 to 15 different constituents working together. No simple solutions have emerged.

Possible replacements under review include chemicals closely related to 6PPD along with newly invented compounds. Some ideas would necessitate significant changes to the rubber-making process. Other ideas are focused on innovative tire designs, a few made with little or no rubber.

Despite the intense effort, finding a replacement for 6PPD is widely recognized as a monumental challenge. That’s because the chemical is exceedingly good at its job — which is to extend the life of tires. For the better part of a century, chemists have been perfecting ways to keep tires from falling apart. Today’s designs cover a wide range of tires with 6PPD as a universal constituent, making tires last longer while increasing safety for drivers and passengers.

“The safety, performance and sustainability” of tires remain the “uncompromising priority” of the U.S. Tire Manufacturer’s Association, said Stephanie Schlea, the organization’s vice president for environment, health, safety and sustainability.

USTMA is leading a consortium of 36 tire-related companies searching for alternatives to 6PPD. As of last August, the consortium was studying 24 potential alternatives, but USTMA officials say that number may have changed as studies advance.

“The chemicals present in tires today all perform specific and integrated functions, and tire composition cannot responsibly be modified without great care, including extensive and rigorous testing,” said Schlea in a letter (pdf) to the Washington Department of Ecology. “Any alternative identified must continue to ensure compliance with Federal Motor Vehicle Safety Standards and other consumer, vehicle and tire manufacturer requirements.”

Rubber formulations vary depending on the type and weight of a vehicle along with different traction specifications for weather and road conditions. While many rubber additives are used in various parts of a tire, 6PPD has become universally accepted as the leading chemical for rubber preservation.

Players in the race for 6PPD alternative

Tire manufacturing facility equipment holding tires

6PPD in action

Here’s how it works: Natural rubber is highly vulnerable to an attack by ground-level ozone, often produced from pollution (including automobile emissions) in the presence of sunlight. The 6PPD on a tire’s surface reacts rapidly with the ozone before it can attack the rubber, which would otherwise crack and eventually break apart.

As 6PPD reacts with ozone, the chemical is used up and must be replaced by 6PPD that migrates to the tire’s surface from the underlying rubber. If 6PPD migrates too slowly, it won’t be there in time to protect the rubber from ozone. If it migrates too quickly, it can dissipate and be used up prematurely. Some experts call 6PPD the “Goldilocks” of tire preservatives for its optimal rate of migration and rapid reaction with ozone.

Any replacement compound must maintain a defensive posture at the surface of the tire, but that’s not the only benefit derived from 6PPD. For example, heat and mechanical stress can create highly reactive free radicals within the rubber polymer chains, which provide structure to the tire. The presence of oxygen encourages chain reactions, which break apart the rubber at the molecular level. The presence of 6PPD quells the chain reactions by “scavenging” free radicals. These antioxidant properties — separate from ozone blockage — mean that 6PPD does double duty in maintaining a tire’s integrity.

In the sidewalls of tires, 6PPD also helps to maintain a flexibility essential to a tire’s performance. Engineers also tout 6PPD’s ability to mix easily into natural rubber and man-made polymers that make up the bulk of a tire. The chemical also performs well during a heating process, called vulcanization, which results in chemical bonding with sulfur, adding strength yet flexibility to the final product.

The multiple attributes of 6PPD make it difficult to find a single chemical to replace it, said Erick Sharp, CEO and founder of ACE Laboratories in Northeast Ohio, a firm involved in the development and testing of potential alternatives to 6PPD.

“We have tried a lot of things, and I don’t think you are going to have a one-for-one replacement for 6PPD,” Sharp said. “The final solution is likely to be a multi-faceted system replacement.”

For example, if a replacement chemical inhibits the vulcanization process — unlike 6PPD — then another chemical might be added to maintain the needed “cure” rate for a specific tire, Sharp said. Virtually all tire manufacturing involves chemicals, called accelerants, that can help establish a cure rate conducive to the desired chemical bonding among raw materials. If the cure rate is altered significantly by new chemicals, then a manufacturing plant might need to be restructured for additional processing, he said.

Of course, any new rubber formulations must be tested for toxicity. An initial test in Sharp’s lab involves exposing new rubber candidates to high levels of ozone and identifying the transformation products released into water. Toxicity, based on published data, is a major factor in deciding whether further study of a particular material is warranted.

Although the challenge is considerable, one or more viable alternatives to 6PPD may not be far away, Sharp said. “With what we have seen, I think all the tools are in the toolbox to get there.”

Urgency for fish populations

Longfellow Creek, which drains a 2,685-acre area in West Seattle, has become Exhibit A for the killing effects of 6PPD-Q on coho salmon. The once-natural stream runs through the heart of the immense Duwamish Industrial Area. Around 1939, it is believed that a localized coho population went extinct, probably because of pollution and fish-passage problems — including a 3,300-foot culvert that carries the stream under parking lots and industrial facilities before releasing the water into the West Duwamish Waterway.

Approximate location of Longfellow Creek which drains a 2,685-acre area in West Seattle. The stream’s pathway includes a 3,300-foot culvert that conveys water under parking lots and industrial facilities before releasing it into the Duwamish River. Map: PSI using Google Earth imagery.

During the 1990s, community groups and volunteers began to restore natural streamside vegetation in an area just upstream of where the stream dives into the long culvert. Around the same time, rocks were added just below that culvert to raise the downstream channel, allowing fish an easier entryway to the culvert when they return from the ocean. In addition, “skylights” were installed by cutting into the top of the culvert to increase light and encourage salmon to swim through the otherwise dark and uninviting pipe.

By the end of the 1990s, coho were beginning to return to Longfellow Creek, a likely result of stream and fish-passage improvements. The first to arrive apparently were strays from hatchery operations. For the first time in years, fair numbers of coho were seen in the vegetated section of Longfellow Creek upstream of the long culvert, as well as areas farther upstream.

But all the work on stream restoration became a somewhat hollow victory, because of the unexpected and gruesome deaths among the returning coho. Many fish that survived the long and tortuous trip from the ocean were dying on the doorstep of their home stream before they could complete their life cycle with reproduction for a new generation.

In some years, the rate of so-called pre-spawn mortality for coho in Longfellow Creek has been estimated as high as 90 percent. Last fall, among the 130 coho that were found dead in the creek, 55 percent had died before spawning, according to observers with Puget Soundkeeper, an environmental group that has been monitoring coho returns since 2015. Another 20 percent were believed to have spawned, but spawning success or failure could not be determined for 24 percent of the dead fish, according to reports.

Another 366 coho were spotted alive in the stream, but that includes an unknown number of fish that may have been counted more than once.

Scientific investigations have found that the highest concentrations of 6PPD-Q can be measured in streams whose watersheds contain a multitude of heavily traveled roads. In Puget Sound, such areas are located in Seattle, Tacoma and Everett, as well as heavily developed areas throughout the region, according to computer models. Concentrations of 6PPD-Q have been found to spike during and shortly after rainstorms, when accumulated toxics are washed off the roads.

Sean Dixon, executive director of Puget Soundkeeper, said he appreciates the research being done to find an alternative to 6PPD, but the urgency doesn’t seem to match the hazard. People need to understand that this tire chemical is one of the most toxic chemicals ever produced by humans, he said, arguing that it has been getting into waters throughout the world and causing serious ecological effects — some known but some yet to be revealed..

“From the perspective of the fish, a ban on 6PPD needs to be in place now,” Dixon said. “You can have the world’s best rainbow trout stream, but if a county road or bridge is nearby, you will have tire particles going down into the stream, and it won’t be the same.”

Dixon noted that it has been more than five years since 6PPD-Q was discovered and 40 years since dying fish were first reported in urban streams. Still, representatives for the tire industry say a solution could be years in the future — and that’s hard to accept, he added.

“It blows my mind in this day and age that we can’t move faster when the whole world recognizes the problem,” Dixon said. “I think we could (move faster) if society decided that we need to.”

Unfortunately, he continued, 6PPD is just one of many problems that salmon encounter in Puget Sound today. Others are warm waters caused by loss of streamside vegetation, fish-passage problems caused by poor road building, and a variety of dangerous chemicals from multiple human sources.

Dixon pointed out that “green infrastructure,” in which natural materials are used to filter stormwater, have been effective at reducing pollution, including 6PPD-Q. Because of the cost of retrofitting stormwater systems in urban areas, many jurisdictions have been slow to make renovations, he noted.

“There are solutions,” Dixon said. “We just need to align our management of the environment with the solutions that we know exist.”

Beyond coho salmon

The search for alternative chemicals that could replace 6PPD is closely connected to toxicological studies examining the chemical’s effects on a multitude of species, including humans. Studies have found that coho salmon are extremely sensitive to 6PPD-Q, succumbing to death at lower concentrations than any other species examined so far — although data remains sparse for many animals.

Recent studies have shown that young coho, as well as older fish, are highly susceptible to 6PPD-Q. If exposed, they can be killed in urban streams during their early rapid-growth period, when coho typically spend their first year of life in freshwater.

Recent information shows that coastal cutthroat trout are nearly as sensitive to 6PPD-Q as coho salmon. Photo: Lukeward6/iNaturalist (CC BY-NC)

Dying coho alerted experts from the beginning about a serious pollution problem in urban streams, and coho remain the most sensitive to 6PPD-Q of any species studied. But new information is continually coming forth. Last year, researchers with the U.S. Geological Survey in Seattle reported that coastal cutthroat trout are nearly as susceptible to the chemical as coho. Other studies have shown that lake trout, brook trout and whitespotted char are somewhat less sensitive. Rainbow trout come next on the sensitivity scale, while Chinook, sockeye and pink salmon are far less sensitive, being able to survive under extreme environmental conditions. Chum salmon seem to be the least susceptible of all.

These reports of sensitivity are based on experiments that measure the minimum concentration of 6PPD-Q that can kill half the fish in a sample when exposed for a specified amount of time. Researchers are just beginning to understand what may happen when fish are exposed at lower, sublethal concentrations. For example, ongoing studies have shown that the chemical can impair muscle function and reduce metabolism, with reports of diminished swimming ability under some conditions.

How 6PPDQ affects fish at the cellular level is not yet well understood, but several studies have revealed that it can cause leaky blood vessels, notably in the brain and gills. Metabolic disruption and immune system activation have been found in some experiments, with potential but uncertain links to vascular dysfunction. Interestingly, some studies suggest that differences in 6PPD-Q sensitivity among species may be related to how quickly different fish are able to detoxify the chemical in their livers.

As for effects on humans, 6PPD-Q has been found in multiple human tissues, and studies on laboratory animals suggest that the chemical may be toxic to people, according to the Washington State Department of Health. More research is needed to determine what human health conditions may be caused by 6PPD-Q and at what levels. Researchers are investigating metabolic stress, reproductive deficiency, developmental impairment, DNA damage and potential effects on various organs.

On a broader scale, 6PPD-Q may disrupt entire ecosystems by affecting organisms at the base of the food web. Limited research so far shows that growth, reproduction and metabolism may be impaired in freshwater invertebrates — including microalgae, water fleas and snails.

First look at alternatives

A first rapid assessment of alternatives to 6PPD was published by the Washington Department of Ecology in November 2021, less than a year after the discovery that 6PPD-Q was killing coho. But the report considered only the toxicity of 6PPD compared to 10 early replacement candidates. It did not evaluate potential transformation products that could result from real-life conditions, such as exposure to ozone.

Six of the chemicals mentioned in the report are closely related to 6PPD, and some could potentially produce quinone forms, the authors acknowledge. If so, those transformation products might be more toxic than the alternatives themselves — such as when ozone transforms 6PPD into the far-more-toxic 6PPD-quinone. With little or no information available about potential transformation products and their effects on coho salmon, the report concluded that more research was needed.

The other four chemicals mentioned in the report appear to be less hazardous than 6PPD-Q, but limited information is available on their transformation products. Three of the four may not sufficiently protect rubber from ozone attack, according to chemical profiles, reinforcing the idea that a simple replacement may not be feasible.

By July 2024, a consortium of tire companies had finalized what is called a “Stage 1” analysis required under California’s Safer Consumer Products law. The analysis selected seven possible alternatives for further study from an original list of 60 candidates given consideration. A month later, during an annual update, the consortium reported in writing that 24 unidentified chemicals were still being reviewed.

Of the seven in the Stage 1 report, four are close relatives of 6PPD. All of those showed promising potential for ozone protection. While their quinone forms had various toxicities, they all appeared to be less hazardous than 6PPD-Q, according to the report. Whether their toxicities are within an acceptable range is a question yet to be answered.

The remaining three are octyl gallate, a food preservative with antioxidant properties; Irganox, an antioxidant compound often used in plastics; and specialized graphene, a substance in which carbon atoms interlock together to form super-thin sheets. Graphene proponents say the material can increase the strength of rubber and possibly reduce, but not eliminate, the need for anti-degradant chemicals. All these are undergoing further review. (See alternatives analysis reports.)

Final recommendations from the consortium are due on Aug. 19 under California regulations. (Tires came under limited state authority in October 2023, when the state’s Department of Toxic Substances Control declared tires with 6PPD as a “priority product.”) Officials with the U.S Tire Manufacturing Association have expressed confidence that one or more viable alternatives to 6PPD will be reported as part of the upcoming “Stage 2” report.

Transformation products resulting from the ozonation of chemicals in the PPD family remain a concern for those seeking alternatives to 6PPD. But the risks became a little clearer recently in a study (pdf) conducted by the U.S. Geological Survey. Instead of using live fish, the study measured the effects of various transformation products on immortalized cell lines from coho salmon, Chinook salmon and rainbow trout.

Increasingly used in toxics studies, immortalized cell lines result from normal cells that are altered in a lab to keep them dividing indefinitely. These laboratory cells respond to chemical exposure like normal cells in many ways. The advantage is that results can be achieved more quickly and consistently without exposing live animals.

Justin Greer, a USGS toxicologist at the Western Fisheries Research Center in Seattle, said studies of tire additives were turned upside down by the discovery of 6PPD-quinone, which is not a tire additive at all. Rather the chemical is the result of the reaction of 6PPD with ozone, a chemical that can destroy a tire under normal driving conditions.

To find an alternative to 6PPD, chemists must understand not only the toxicity of the tire additive but also the toxicity of the transformation products generated through chemical reactions on the road and in the environment, Greer said.

“Specifically,” he added, “tire chemicals are meant to react under normal conditions — so we know that the transformation products are important.”

The USGS study examined the effect of ozonation products — include quinone forms — of five compounds closely related to 6PPD, including some still under consideration as potential replacements for the tire additive.

As expected, 6PPD-Q was highly toxic to coho salmon, as revealed by a disruption in metabolic activity in the laboratory-grown cells. Two related chemicals, 7PPD-Q and IPPD-Q showed metabolic declines in coho cells but at higher concentrations than for 6PPD-Q. Metabolic activity for the Chinook salmon and rainbow trout cells were not significantly affected by the quinone forms of either 7PPD or IPPD.

Expanding the experiment, the researchers looked at the full mixture of transformation products, many unidentified, following ozone treatment of the base PPD chemicals.

“We observed that ozonated mixtures of 6PPD, 7PPD and IPPD were typically more toxic that the purified quinones,” states a report on the project. Those findings suggest that the PPD-quinones are not the only transformation products harmful to fish; others not only exist but can add to the toxicity of the quinones alone.

For the Chinook cell line, no effects were seen when exposed to pure 7PPD-quinone, a single transformation product. Yet multiple transformation products resulting from ozonation of 7PPD produced a measurable reduction in metabolic activity. Likewise, for rainbow trout, the ozonated mixtures produced greater toxic effects than pure quinones not only for 7PPD but also 6PPD and IPPD.

While 6PPD may have a variety of transformation products, it appears that 6PPD-Q, the quinone form, is by far the most potent to coho salmon. The effects of other chemicals formed during ozonation are not even comparable.

For three other relatives of 6PPD, namely DPPD, 77PD and CCPD, no effects were seen in the lab-grown cells of coho, chinook or rainbow trout when exposed to their quinone forms. The researchers note, however, that immortalized coho cells are less sensitive than living coho cells, so the question of sensitivity among all the test cells warrants further examination.

While these experiments clearly demonstrate the importance of studying the full range of transformation products, this study did not try to identify the actual chemicals in the mix. Consequently, the authors could not entirely rule out the possibility that unknown contaminants had influenced the results.

About the Author

Christopher Dunagan is a senior writer at the Puget Sound Institute.

Go, fry, go! Baby coho salmon released into local streams

May 17, 2026

Link to My Edmonds News article

Several thousand baby coho salmon from the Willow Creek Salmon Hatchery in Edmonds were released into local streams on Saturday.

*Imogen and Adelia ready to release baby salmon into Willo Creek. (Photo by Emily Benson)*

This hatchery has raised salmon since the mid-1980s, and in recent years, under management by Sound Salmon Solutions, has focused on re-introducing and bolstering coho salmon populations in Edmonds’ streams, such as Shell Creek, Perrinville Creek, Willow Creek, Shellabarger Creek, Lunds Gulch Creek and Northstream Creek.

*Adelia Benson with her cup of baby salmon.*

Releases of baby coho salmon (called ‘salmon fry’) into local streams now involve volunteers of all ages to promote public engagement in enhancement of the quality stream habitat that these fish need to survive.

Saturday was no different with adults, students, and young families helping release the salmon fry into Shell Creek in Yost Park and into Willow Creek next to the Hatchery.

*Hatchery Manage Megan Moran scoops salmon into cups.*

*Fry are off and running, er, swimming.*

Council to consider amendment to Perrinville Creek consultant contract April 28

April 26, 2026

Link to My Edmonds News article

The Edmonds City Council at its Tuesday, April 28 business meeting will consider a $383,456 amendment to consultant contract for the second phase of a flow reduction study in the Perrinville drainage basin.

The city has been working for years to develop strategies to control flooding on Perrinville Creek between Talbot Road and Puget Sound. A flow reduction study in 2015 resulted in a list of recommendations, from drainage improvements to a municipal raingarden program.

The City of Lynnwood, which sends stormwater runoff to the basin, is partnering with the Edmonds on the project. Both cities were awarded a $469,200 state Department of Ecology grant toward this effort to analyze the problem, which requires $82,800 in local matching funds from Edmonds and Lynnwood. The grant and matching funds are split bet

According to the staff agenda memo regarding this item, the grant and matching funds are split between the two cities. The amendment to the professional services agreement is $383,456 and includes a $20,455 management reserve, the memo states.

“In 2024, Edmonds and Lynnwood entered into an interlocal agreement and contracted Herrera Environmental Consultants to provide design services for the study update, the memo says. “Phase 1 of the study update involved a review of the recommended projects and planning level design and estimating work of new projects. Projects were rated based on criteria including impact on flows, constructability and cost effectiveness.”

The contract’s second phase “will include a more in-depth analysis, including geotechnical investigations for the sites that include mitigation via infiltration, for the 10 highest-scoring flow reduction projects from first phase of the study update. Once the analysis is completed, the project rankings will be reassessed and the consultant will provide conceptual design for the six highest-scoring sites.”

Other items on the council agenda include:

2025 Prosecutor’s Office Annual Report
2025 Public Defender’s Office Annual Report

The council will also hear an update from Police Chief Loi Dawkins on the public safety sales tax.

The meeting will begin at 6 p.m. in the council chambers, Public Safety Complex, 250 5th Ave. N., Edmonds. You can also access the meeting remotely at this Zoom link. Or listen by phone at +1 253 215 8782. The meeting ID is 957 9848 4261.

St. Thomas More fourth graders release baby salmon into Willow Creek

April 18, 2026

Link to My Edmonds News article

*A student releasing salmon one cup at a time. (Photos courtesy Joe Scordino)*

Fourth graders from St Thomas More School in Lynnwood were enthralled this week to release 100 coho salmon babies that they had successfully raised from eggs in their school aquarium, according Edmonds Stream Team leader Joe Scordino.

As part of the Washington Department of Fish and Wildlife (WDFW) Salmon in Schools program (now called School Cooperative Program), the Edmonds Stream Team obtained 100 coho salmon eggs in January from WDFW’s Issaquah Hatchery and delivered them to the fourth graders’ aquarium at St. Thomas More School.

*The students raised 100 coho salmon babies from eggs in their school aquarium.*

*The St. Thomas More fourth-grade class with their salmon in a transport bucket.*

Raising baby salmon has been a special part of being in 4th grade at St. Thomas More School for many years, Scordino said. The students learn about the life cycle of salmon and the importance of healthy streams where these fish live — and get to actually see salmon eggs hatch and transition from the “alevin” stage (with a yolk sac) to the “fry” stage when they begin feeding in the aquarium.

“Over 500 schools in Washington have participated in the Salmon in Schools program, and it no longer surprises me when a young adult will tell me they still remember the joy of having a salmon aquarium at their school,” Scordino said.

*Edmonds Stream Team leader Joe Scordino, right, watches as a student gets ready to release a baby salmon into Willow Creek.*

“This year was especially exciting for St. Thomas More in that the fourth graders, with the help of teacher Kari Hopper, made sure all of the 100 salmon eggs hatched and became salmon fry that were then carefully released into Willow Creek — no mortalities,” Scordino added.

Stream Team helps bring salmon back to Edmonds

March 25, 2026
By Joe Scordino

PRESS RELEASE Bringing Salmon Back to Edmonds Download

Link to My Edmonds News article
Link to Edmonds Beacon article

It’s now that time of year when the Edmonds Stream Team and Sound Salmon Solutions are working with community volunteers to place ‘baby’ coho salmon from the Willow Creek Salmon Hatchery in Edmonds into local creeks. The 2- to 3-month-old ‘baby’ coho (called salmon ‘fry’) will bolster local populations whose habitat has been affected by development and stormwater.

At Perrinville Creek, neighborhood families, along with students from Meadowdale High School, helped release 4,000 coho salmon fry into the upper creek (near the Perrinville Post Office).

At Shellabarger Creek along the Hwy 104 Marsh Restoration Project, members of the Edmonds Rotary Club and restoration volunteers captured 1,000 coho salmon fry from the Hatchery pond and released them into the restored, re-opened creek (previously enmeshed with invasive bittersweet nightshade).

Next Sunday, March 29, 5,000 coho fry will be released into Lunds Gulch Creek in Meadowdale Beach Park around 10:00am near the wood bridge (visitors are welcome to watch). On May 16, Sound Salmon Solutions will release 3,500 coho into Shell Creek in Yost Park (see SSS website).

The two-inch coho salmon fry will spend their first year of life in freshwater streams and then go out to sea where they’ll grow into 2-foot+ adult salmon. Then in fall of 2028, the survivors will return to freshwater streams as spawning adult salmon to create future salmon generations.
The adult spawners will return to the creeks where they were born, or in the case of these fry to the creeks that they lived in (and imprinted to) prior to going out to sea. Unfortunately, for the Perrinville Creek salmon, they won’t be able to return unless the blockage the City placed in 2021 is removed (for detail on the blockage see 7/15/25 My Edmonds News article on the Edmonds Environmental Council’s complaint about the City’s illegal diversion structures).

The community salmon enhancement program is authorized under Cooperative Agreements between the Washington Dept. of Fish and Wildlife, the Edmonds Stream Team, and Sound Salmon Solutions.

Joe Scordino, Project Leader
Edmonds Stream Team
Edmonds.Envir.Council@gmail.com

The Edmonds Stream Team is a community all-volunteer Citizen Science project to monitor and improve the condition of Edmonds creeks and nearshore wetlands to enhance salmon and wildlife populations (and benefit people who appreciate preservation of our natural resources)

Alliance of Citizens for Edmonds joins Edmonds Environmental Council: Goal is to ‘protect and preserve the local environment’

March 14, 2026

Link to My Edmonds News article

The Edmonds Environmental Council (EEC) said Saturday it is welcoming prior members of the Alliance of Citizens for Edmonds (ACE) into its membership.

According to a news release from EEC Board President Joe Scordino, the ACE board of directors notified their membership in December 2025 that ACE was closing as an active organization at year-end — but that the board would explore having its members become part of another like-minded organization.

Alliance of Citizens for Edmonds joins Edmonds Environmental Council

Posted Monday, March 16, 2026

Link to Beacon article

Alliance of Citizens for Edmonds joins Edmonds Environmental Council to help protect and preserve the local environment

The Edmonds Environmental Council (EEC) is welcoming prior members of the Alliance of Citizens for Edmonds (ACE) in joining the EEC.

Edmonds issues moratorium on development in Deer Creek aquifer

The ordinance passed unanimously Tuesday, giving the city time to complete a study on PFAS in the area.

By Jenna Peterson
February 11, 2026

Link to Everett Herald article

The Edmonds City Council on Tuesday, Jan. 6 in Edmonds, Washington. (Will Geschke / The Herald)

EVERETT — The Edmonds City Council unanimously approved a moratorium on development near Deer Creek on Tuesday following code changes that have raised difficulties for processing permits.

Concerns over “forever chemicals” pose biosolids challenge for treatment plants

By Sarah DeWeerdt
Published February 10, 2026

Increasing concerns surround PFAS in products from wastewater treatment plants. How great a risk do they pose, and are there feasible approaches to removing them? We continue our occasional series on water quality and wastewater management in Puget Sound. Funding for the series is provided in part by King County.

A crisis emerges across the US as ‘forever chemicals’ quietly contaminate drinking water wells

By MICHAEL PHILLIS and HELEN WIEFFERING
February 2, 2026

Link to AP News article

The town hall in Stella, Wis., on Friday, Dec. 5, 2025. (AP Photo/Morry Gash)

STELLA, Wis. (AP) — Kristen Hanneman made a small decision in 2022 that would upend life for her entire town.

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.

Report reveals how urban runoff continues to threaten coho salmon health

January 27, 2026
Puget Soundkeeper

Link to My Edmonds News article

Pre-spawn mortality – *Photo courtesy Puget Soundkeeper*

Since 2015, Puget Soundkeeper has monitored coho salmon health in Seattle’s Longfellow Creek, producing data on the impacts of urban pollution on salmon survival. For years, Longfellow Creek has been the epicenter of research studying the effects of 6PPD-quinone — a toxic tire chemical lethal to coho salmon.

According to a Puget Soundkeeper news release, exposure to 6PPD-quinone causes a condition called Urban Runoff Mortality Syndrome (URMS), a disease characterized by symptoms such as disorientation and gasping for air, often killing coho within 24 hours. Furthermore, this chemical has been strongly linked to Pre-Spawn Mortality (PSM), where adult salmon die before successfully reproducing, the news release said.

Puget Soundkeeper’s annual Pre-Spawn Mortality Survey analyzes the spawning success of coho salmon in Longfellow Creek to better understand the impacts of 6PPD-quinone. From October through December, trained volunteers count and dissect returning coho salmon, particularly assessing the presence of eggs and milt to determine whether spawning was successful.

Results from the 2025 study show that 55.5% of coho salmon died before spawning. This aligns with data collected since 2015, which shows that 49-90% of returning salmon die before reproducing each year.

“This level of pre-spawn mortality is devastating,” said Ewan Henderson, clean water program specialist at Puget Soundkeeper. “The dramatic reduction in successful spawning opportunities is a huge blow to our ecosystems, particularly for our resident orcas who already face major challenges as their food sources dwindle.”

According to the press release, Green Stormwater Infrastructure (GSI) projects, such as rain gardens or bioswales, can effectively remove toxins from runoff and prevent harmful chemicals from entering local waters. In addition to GSI projects, a bill (HB 2421) aimed at removing 6PPD from tires was introduced to the Washington State House and Senate Environment Committees last week.

Puget Soundkeeper will be recruiting the next cohort of salmon surveyors in August. More information will be made available on their website.

To learn more about the 2025 Salmon Survey report results, visit pugetsoundkeeper.org/volunteer/salmon-surveys.

Study finds juvenile coho salmon at risk from deadly tire chemical

By Jeff Rice
Puget Sound Institute
Published January 9, 2026

Link to Puget Sound Institute, UW Tacoma article

*Juvenile coho salmon. Adobe stock image*

Untold numbers of hatchery fish may be dying from exposure to tire-contaminated runoff, according to a new study.

Responding to concerns about drinking water protection, Edmonds Council approves critical areas ordinance

By Teresa Wippel
January 7, 2026

Link to My Edmonds News article

*Councilmember Susan Paine, center, makes a point about the critical areas ordinance during a Q&A with staff Tuesday night.*

Key takeaways:

Michelle Dotsch elected council president, Jenna Nand selected president pro tem.
Numerous residents testify in support of a measure they say would better protect the Deer Creek critical aquifer recharge area (CARA) — and council approves it 4-3.
Councilmembers sworn in and last year’s council president gets a sendoff.
Council votes to increase the city’s transportation impact fees.