Are tires on our dock or boat really that harmful to the environment?
Updated: Oct 10
(Artile updated October 10, 2026)
Q: Do tires in and over the water pose a serious environmental risk to our lake? Tires used as dock or boat bumpers don’t seem like a concern, since there’s no friction to break them down. Isn’t the bigger problem the tire dust coming off the interstate?
A: It’s a fair question, and the highway is a major source of tire pollution. But the “no friction, no problem” idea misses how tire chemicals behave in water. There is solid science behind removing dock tires, and it’s one of the easier fixes we have.
Leaching doesn’t need friction. The chemical of concern is 6PPD-quinone. It forms when 6PPD, an additive that keeps tires from cracking, reacts with ozone in the air. That can happen on a road, or on the surface of a tire hanging at your dock. Once a tire is in the water, 6PPD, any 6PPD-quinone that has formed, and other tire compounds can seep out with no rubbing at all. Leaching is a chemical process, not just a mechanical one.
Tires in water still break down. A dock tire is not inert. Sunlight breaks down the rubber, oxidation keeps working at the surface, wet-dry and seasonal temperature swings stress the material, and microbes and biofouling speed up the decay. The result is a slow but continuous release of tiny particles over years.
Our local salmon make this personal. Research led by Washington State University and others found that 6PPD-quinone is acutely toxic to coho salmon. At concentrations found in the environment, it can kill them within hours, a pattern known as “urban runoff mortality syndrome.” Most of the pollution comes from roads, but every added source adds to the total. That matters most in calm, slow-flushing places like marinas and around floating homes.
A dock tire is a different kind of source than a highway. Runoff from a highway is spread out and arrives in pulses. A tire on your dock:
Sits right in the water, often where there’s little circulation
Can become a constant, local leaching “hotspot”
Is often near the shallow habitat where young fish and invertebrates feed and shelter
So who’s right? Highways are the dominant source of 6PPD-quinone. But dock tires are a local source that never shuts off, and they sit exactly where sensitive species live. Because we control them, taking them out is a low-cost, sure-thing step, unlike trying to fix interstate runoff.
The Most Important Things to Know:
6PPD-quinone forms when the tire additive 6PPD reacts with ozone, and it is highly toxic to coho salmon.
Tires leach chemicals in water without any friction. Leaching is chemical, not just mechanical.
Dock tires keep degrading from sunlight, oxidation, temperature swings and microbes, shedding particles for years.
Highways are the biggest source, but dock tires are a continuous, local source in the shallow habitat fish rely on.
Replacing dock tires is effective, and the fix is entirely in our control.
Whatever you replace them with, it must be free of 6PPD.
Q: What specifically should I replace my tires with?
A: The key is to stay away from anything containing 6PPD.
“After speaking with Katheryn Hayes at the FHA, we reached out to her suggested manufacturers to explore product options,” said Derek Voelker of Seattle Dive Company. “We selected products that are durable, provide effective protection, and are completely 6PPD-free. Crucially, these bumpers are engineered specifically for docks - not multipurpose.”
The right choice will vary with your home’s needs and the durability and price you can afford. Ask your favorite dive company or handyman to recommend a product for your situation, and make sure it is doesn't contain 6PPD.
If you’d rather do it yourself, these suppliers carry standard dock products that are made entirely of PVC or FOAM and do not contain 6PPD.
Fisheries Supply: environmentally safe dock fenders
West Marine: PVC bumpers
LFS Marine Supplies: PVC dock bumpers
Industrial dock products can be specified in 100% virgin EPDM rubber, marine-grade polyurethane, or virgin PVC/EVA. This avoids natural rubber and SBR compounds, which often contain recycled tire crumb or tire antiozonants that continuously leach into the water. Ask for certifications, reports verifying no crumb rubber fillers are used in the extrusion process - and no 6PPD.
1. Direct Marine Extruders & Fabricators (EPDM D-Bores / D-Fenders)
Duramax Marine - commercial marine bumpers and D-fenders (100% EPDM rubber, Series 900 D-Shape and Series 100 Tapered D)
Pacific Marine & Industrial - industrial extruded fenders (EPDM without crumb additives)
The Rubber Company (select virgin EPDM compound or marine grade PVC instead of standard, natural rubber/SBR blends)
FenderTec (stocks and machines heavy-duty D-fenders with custom compounding available)
2. Ready-to-Ship Commercial Suppliers
VXB Bearings & Industrial (modular pre-drilled bumpers)
Haven Dock & Marine (100% prime virgin UV-stabilized PVC)
Q: What else can I do?
A: Here are six steps, from easiest to most neighborly:
Carpool and use public transportation when you can. Fewer miles driven means fewer tires shedding onto roadways.
Keep your car’s tires properly inflated. They last longer and shed less harmful dust.
Dispose of old tires properly, through your tire dealer or a transfer station.
Use a commercial car wash, not your driveway or a parking lot. Commercial washes are required to filter their wastewater, so soap, grime and tire particles don’t flow into the lake.
Look around your house, dock and marina. If tires are being used as fenders, talk to the owners about swapping in less toxic options. Ask us what we’ve learned about alternatives. We have solid learnings from Kenmore Air’s upgrades.
Spread the word. Most people have never heard of 6PPD.
Q: Who else is working to clean up Lake Union?
A: The Floating Homes Association donates to Clean Lake Union, a Seattle nonprofit whose mission since 2012 has been to raise awareness of local water quality and use practical solutions to clean up our waterways.
It began when founder Mark Grey found polluted runoff pouring into Lake Union from a storm drain on Eastern Avenue. Working with partners such as Salmon Safe and The Nature Conservancy, the group grew into a nonprofit that now works on waterways and bridges beyond the lake. Its flagship effort is the Aurora Bridge Bioswales project, which treats the nearly 2 million gallons of polluted runoff that wash off the bridge into Lake Union and the Fremont Cut each year. It is also known for its annual Paddle Race fundraiser, which raised nearly $200,000 in 2026.
The Floating Homes Association also donates to the Puget Soundkeeper Alliance, a Seattle nonprofit who has been fighting for clean water throughout the Puget Sounds since 1984. They have several paddle cleanups removing marine debris from Lake Union every year and worked directly with Kenmore Air Harbors when they replaced tires from their docks with a non-toxic alternative in 2025.
“We were honored to play a role in helping protect Washington’s iconic salmon,” said David Gudgel, past President of Kenmore Air. “When we became aware of the dangers posed by 6PPD-q, we knew we needed to find a solution. Thanks to the Puyallup Tribe and Puget Soundkeeper Alliance, we were able to identify a safer alternative that will be installed at our Kenmore, Lake Union and Roche Harbor float docks by late spring 2025."
For questions about our FHA Tire Removal Program, contact Environmental Chair Katheryn Hayes at environment@seattlefloatinghomes.org
More reading: Pacific Salmon at a Crossroads, “Legacy of Chemical Pollution from an Underwater Tire Dump” (2025, MDPI Journal Environments); Note that tires contain a chemical cocktail of ingredients, not just 6PPD and many of them have not been studied well, so in general, if we have a less toxic alternative, we should use it. https://www.wastormwatercenter.org/research/tiresandsalmon/
Sources include:
(1) Anna S. Bachmann, Clean Water Program Director - Puget Soundkeeper Alliance
Mobile: 360-821-9859 - anna@pugetsoundkeeper.org
(2) Katheryn Hayes, FHA Environmental Chair
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