Toxic Tires: Getting 6PPD Out

The Pacific Coast Federation of Fishermen’s Associations and the fishing folks we represent have never been timid about taking on hard tasks, especially when it comes to protecting our fisheries.

PCFFA was formed in 1976 for the specific purpose of protecting—and where necessary, restoring—sustainable commercial fishing as a way of life, including using the combined strength of the many local fishermen’s organizations that make up the PCFFA to take on all the hard tasks involved.

Since salmon has long been a major West Coast ocean fishery (in spite of recent collapses) our mission also means working hard to protect and restore damaged salmon habitat wherever salmon occur, all the way up to the tops of coastal watersheds.

PCFFA’s sister organization, the Institute for Fisheries Resources (IFR) was founded by PCFFA in 1992 specifically to carry out and help fund PCFFA’s many fish habitat conservation and recovery programs, especially for damaged salmon runs. The institute has just celebrated its 30th anniversary.

In our efforts to protect salmon habitat, PCFFA/IFR has taken on many other major industries to put a stop to once-common land and water use practices by some of other industries that damage and can destroy the very fisheries upon which our members depend for their livelihoods.  Some of our successes over the last 30 years include:

Leading efforts to put an end to prior federal efforts to exploit the entire West Coast (including major fishing grounds) for offshore oil development, with drilling moratoriums now in effect on most of the West Coast.

Making the dumping of radioactive waste in U.S. ocean waters (and fishing grounds) illegal.

Putting in place more science-based federal and state forestry rules that better protect salmon-bearing streams from past highly destructive logging practices. 

Ending suction dredge mining in salmon-bearing streams in both California and Oregon.

Taking on the entire U.S. pesticide industry and securing major restrictions on the use of 57 different pesticides and herbicides that keep those chemicals from being sprayed near and on salmon-bearing rivers.

Suing the fossil-fuel industry (PCFFA vs. Chevron, et al.) for the damages greenhouse gasses generated by their fossil fuels have done to our West Coast oceans. The results—multiple fisheries failures and climate change dislocations—impacts that are increasing—that the fossil fuel industry deliberately lied to the public about for decades.

Working to remove several major fish-killing dams. Our latest ongoing project is the destruction of four Klamath Basin dams in what will be the largest dam removal and largest salmon habitat restoration projects to date. 

It should be no surprise then that PCFFA and IFR now have taken on the entire U.S. rubber tire manufacturing industry, to force them to discontinue the use of a fish-killing chemical in their tires called 6PPD (now a pervasive pollutant in urban runoff) that is highly toxic to salmon, especially to Coho salmon already on the verge of extinction.  

Why Pick on Rubber Tires?

Hundreds of millions of rubber tires of the sort in use on most cars gradually wear down and shed tiny particles of rubber as they are used on roads. These particles then wash into nearby streams as part of urban runoff.

But this runoff has been known since the late 1980’s to be highly toxic to fish, creating what is known as “urban runoff mortality syndrome” or URMS, also known as Coho pre-spawn mortality. This kills many adult salmon (especially Coho) before they can spawn.

Lethal effects of roadway runoff also have an impact on both pre-spawn and juvenile salmon, and are harmful to many other species of aquatic organisms as well.

But for a long time, nobody actually knew what was really going on to cause this runoff mortality, or what was actually in the runoff that was really killing these fish. That is, until the specific chemical in this runoff was identified by scientists in a breakthrough paper (Tian, et al. (2021) published in January 2021 (see citation below).

It turns out that most modern black tires are made with a chemical called “6PPD” (technically known as N-(1,3-dimethylbutyl)-N’-phenyl-p-phenylenediamine) that is intended to protect the rubber in them from oxidizing more rapidly in atmospheric ozone. But it then turns out that 6PPD itself decomposes—when exposed to oxygen in the environment—to a breakdown byproduct called “6PPD-quinone”—and this byproduct is one of the most toxic chemicals killing fish that is currently known!  It is toxic to Coho salmon at concentrations of less than one part per billion.

Urban runoff of tire-connected 6PPD-quinone frequently exceeds fatal concentrations in most major cities. 6PPD-quinone also affects Chinook salmon and other fish, though Coho salmon seem to be particularly sensitive. Perhaps that’s because this species of salmon spends the most time in inland streams and is therefore exposed for longer time periods than Chinook.

But Chinook and many other aquatic species are also definitely affected by this runoff chemical in most urban areas. This would also be true in rivers flowing through multiple major urban centers, such as the Sacramento and Columbia Rivers.

For many years, Coho populations in Northern California and the Pacific Northwest have been declining rapidly for many inter-related reasons. Coho salmon are now so rare that they are protected almost everywhere in these areas as “threatened with extinction” under the federal (and some state) Endangered Species Acts (ESA).

It now turns out that 6PPD-quinone laced urban runoff is one of the drivers of their decline.  This means that the tire companies, by putting 6PPD in their tires, are committing a widespread (and illegal) “take” of not only Coho as an ESA-listed species, but also of Chinook as well as other ESA-listed fish (such as steelhead) where they co-occur.  

These ESA-listed salmonid species impacts are the basis of the PCFFA/IFR 60-Day Notice of Intent to Sue issued Aug. 15 (see citation below). We expect to file this U.S. Federal District Court case sometime shortly after Oct. 15, when the 60-day notice period ends.

Finding Solutions?

Are there solutions to this problem for the tire manufacturers? Of course there are.

The most obvious is to find some other, much less toxic, alternative to 6PPD to protect tires from rubber oxidation. To their credit, some of these companies are actively working on finding alternatives with many potential candidates already identified.

But there are unfortunately still some institutional barriers to their success in finding those alternatives, including (a) the process and ingredients that each company uses in making their tires are trade secrets they will not share and do not want known; (b) as economic competitors, they are hesitant to cooperate with each other in doing or funding joint research, especially with proprietary information involved; (c) many alternatives also may have toxicity problems or other downsides, and; (d) retooling their manufacturing processes will take time and money, neither of which most companies want to expend, certainly not on their own, unless others in their industry also are forced to do so.

And simple institutional inertia—the unwillingness to change unless it becomes necessary—also plays a role in the slowness to date of the efforts of the tire industry to find alternatives. Our ESA-based lawsuit, which is being brought against the entire U.S. tire manufacturing industry, is intended to create additional industry-wide incentives to make those changes as soon as possible—under court order if necessary.

Nevertheless, to the tire industry’s credit, there have been some reports, conferences and workshops to find less-toxic alternatives to 6PPD. Some of them are cited below.

There are also efforts by state governments to formally regulate the use of 6PPD to provide stronger incentives to the whole industry to change. When government regulations create both a level playing field for all economic competitors as well as deadlines, companies are much more likely to cooperate in solving a problem they all must face.

The state of California, for instance, just classified 6PPD as a “priority product” under its Department of Toxic Substances Control (DTSC) registry, one of only seven products now regulated under its Safter Consumer Products designation. That designation becomes effective Oct. 1.

As a result of the “priority product” listing, foreign and domestic manufacturers of motor vehicle tires whose products enter the stream of commerce in California will have until Nov. 30, to submit Priority Product Notifications to DTSC identifying those products.

The notifications must be submitted through DTSC’s online Safer Consumer Products Information Management System (CalSAFER), making them public record to consumers and product safety advocates.

Also under California’s Safer Consumer Products regulations, in addition to timely submitting Priority Product Notifications, manufacturers of tires containing 6PPD now will have until March 30, 2024, to take one of four additional actions with respect to their products: 1) submit a notification of intent to remove the chemical from their products; 2) submit a notification of intent to remove their products from the California market; 3) submit a notification of intent to replace 6PPD with a different chemical in their products, or 4) submit a preliminary alternatives analysis examining possible replacements for 6PPD in their products.

Mitigating Impacts to Fish

Another approach being considered in California would be to limit and prevent as much urban runoff reaching nearby streams as possible. This is the point of a bill (AB 756) now in the California Legislature’s 2023-2024 Regular Session.

AB 756 would create a Department of Transportation program for installing natural bioretention and biofiltration systems, after some pilot programs and studies, commencing in January 2027, over a period of the next 10 years to catch, filter and prevent discharges of 6PPD and 6PPD-quinone wherever they could reach salmon-bearing streams.

That bill is currently stalled for this half of the session, but is a two-year bill that may well surface in the second half (2024) of the state’s legislative session.

Washington state’s legislature recently approved $2.7 million for developing a 6PPD action plan and completing an assessment of replacement options for the chemical, along with about $5.2 million for addressing toxic tire wear material in stormwater.

These sorts of mitigation and pollution prevention programs are also consistent with the federal Clean Water Act and state water quality laws. Preventing pollution is always cheaper and more effective than trying to clean it up afterward.

In short, the poisoning of West Coast salmon by 6PPD and its breakdown products from rubber tire pollution is now a known impact, but is a preventable problem that can be eliminated by the manufacturers if they find less toxic or non-toxic alternatives.

But the impact on our remaining (and rapidly diminishing) salmon populations cannot be ignored any longer. To make sure this problem is promptly corrected, PCFFA/IFR is bringing this suit. No more dithering!

But we also intend to work with the manufacturers toward finding alternatives, and with state water quality agencies in finding ways to mitigate impacts that may persist. To help save the salmon that are being poisoned by the toxic stew of urban runoff, we can do nothing less.    

Glen Spain is the Acting Executive Director of the Pacific Coast Federation of Fishermen’s Associations (PCFFA) and its sister organization, the Institute for Fisheries Resources (IFR). He is also the PFMC-appointed Commercial Fisheries Representative to the PFMC’s Habitat Committee. He can be reached by email at and by phone at the PCFFA/IFR Northwest Regional Office: (541) 689-2000. PCFFA’s website is  IFR’s website is