Are tires on our dock or boat really that harmful to the environment?

QUESTION: Are having tires in and over the water so serious of an environmental risk to our lake? Tires that are reused as a dock or boat bumper to me don’t seem a serious concern since there’s no friction to cause them to break down. Isn’t the bigger problem the tire dust coming off the interstate?

ANSWER:

This pushback is understandable—but it’s based on an incomplete picture of how tire-derived contaminants behave in aquatic environments. There is solid science points to showing that removing dock tires is a meaningful, defensible action.

First, the key issue isn’t just friction—it’s leaching and transformation. The compound we're concerned about, 6PPD-quinone, forms when the tire additive 6PPD reacts with ozone in the air. This transformation can happen before tire particles ever reach the water (e.g., on roads). But once tire material (or whole tires) is in the water, 6PPD (and any 6PPD-quinone that forms on the tire when exposed to air) as well as any other compounds in the tire can leach out—even without mechanical abrasion. So, the “no friction = no problem” argument doesn’t hold. Leaching is a chemical process, not just a mechanical one.

Second, tires in water still degrade—just differently. Even when used as dock bumpers, tires are not inert: UV radiation (sunlight) breaks down rubber polymers, Oxidation continues at the surface (which can still form 6PPD-q), Temperature cycling (wet/dry, seasonal changes) stresses the material, and biofouling and microbial activity can accelerate breakdown. This leads to micro- and nano-particle shedding, albeit at a slower rate than on highways—but still continuous over long timeframes.

Third, because of the direct link to salmon mortality in the Pacific Northwest, the case for just getting all tires out from where they don't need to be becomes particularly strong locally. Research led by Washington State University and others has shown:

• 6PPD-quinone is acutely toxic to coho salmon

• Exposure can cause rapid mortality (within hours), what we call "urban runoff mortality syndrome," at environmentally relevant concentrations

Even though much of the load comes from roads, any additional source contributes to cumulative exposure, especially in enclosed or low-flushing areas like marinas.

Fourth, tires act as localized contamination reservoirs. Dock tires create a different risk profile than roadway runoff:

• They sit directly in the water column, often in low-circulation zones

• They can create chronic, localized leaching “hotspots”

• Juvenile fish and invertebrates often use docks as habitat, thus leading to higher exposure risk

While highways are a major source, dock tires are a point-source amplifier in sensitive nearshore environments.

Yes, highway tires are a dominant source of 6PPD-quinone.... but dock tires are:

• A controllable, local source

• A continuous emitter

• Located exactly where sensitive species are present

From a management standpoint, removing them is a low-cost, high-certainty intervention compared to trying to solve interstate runoff.

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.

Source:

(1) Anna S. Bachmann, Clean Water Program Director - Puget Soundkeeper Alliance

Mobile: 360-821-9859 - anna@pugetsoundkeeper.org

(2) Katheryn Hayes, FHA Environmental Chair