6PPD is an organic compound. Since the 1960s it has been used as a chemical additive to help preserve the rubber in tires. One unexpected side-effect has been that, as tires degenerate through use, particles of 6PPD shed and react with ground level ozone to form 6PPD-quinone. In 2020, scientists traced 6PPD-quinone as the toxic culprit for wide-spread salmon die-off across the Pacific Northwest. How? After rains, storm water runoff carries 6PPD-quinone to area rivers, streams and creeks, home to salmon and other living things. It turns out that 6PPD-quinone is highly toxic to some animals and that young coho salmon die within hours after exposure, devastating the life cycle of salmon. This reaction reverberates exponentially and affects regional ecosystems and the indigenous communities and cultures who live there.
One result of the work of tribal educators, scientists, and other activists to highlight 6PPD as a toxic hazard is that In Fall 2023, the California Department of Toxic Substances Control (DTSC) instituted new regulations that will require tire manufacturers to seek alternatives to 6PPD.
6PPD-QUIONINE: SOURCES
Vehicle tires contain the chemical 6PPD, which helps prevent tire degradation. As tires wear down through contact with the road, they release particles containing 6PPD into the environment. Once these particles come into contact with oxygen, it becomes 6PPD-quinine. Rainwater washes these particles from hard surfaces like parking lots, streets, and bridges into streams and other bodies of water via stormwater runoff. These tire wear particles can also settle on surfaces, soils, and plants, potentially leading to plant uptake and human exposure through dermal contact or ingestion.
6PPD: VULNERABLE GROUPS
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6PPD-QUIONINE: ECOLOGICAL EFFECTS
6PPD-quinone in surface waters can be ingested and absorbed by fish, and these contaminated organisms can then be ingested by humans and other species. Data indicates that 6PPD-quinone is highly toxic to fish, with a 2021 study linking coho salmon deaths to the presence of 6PPD-quinone in stormwater. Even brief exposures to concentrations were lethal for coho salmon. This poses a significant issue for salmon populations, which are culturally, commercially, and ecologically vital, with some coho salmon populations already endangered or threatened. Acute symptoms in fish exposed to 6PPD-quinone resemble respiratory distress, including gasping at the water’s surface and fin splaying, with their symptoms appearing within 90 minutes of exposure. Research has shown that exposure to 6PPD causes fluid to leak from blood vessels in the gills and brains of coho salmon, compromising their blood-brain barrier and potentially disrupting cellular energy production. The inability of sensitive species to metabolize 6PPD into a less toxic form may further exacerbate its toxicity.
6PPD-QUIONINE: HEALTH EFFECTS
The health effects of 6PPD-quinone are currently under-researched, but early studies indicate significant risks. 6PPD is known to cause contact dermatitis and is classified as a Category 1B reproductive toxicant by the European Chemicals Agency, with exposed rates experiencing prolonged and difficult births, sometimes resulting in death. To understand the potential impact on humans and other mammals, researchers have exposed mice to 6PPD-Q, finding the chemical in various tissues, including the kidney, lung, testis, liver, spleen, heart, and muscle. Notably, 6PPD-Q accumulated at high levels in fatty tissues and persisted longer, aligning with the understanding that fatty tissues can store certain toxic chemicals. The presence of 6PPD-Q in lung tissue suggests that it can affect the lungs through contaminated food or water, even without direct inhalation of polluted air.
CRITICAL CASE: PUGET SOUND, WASHINGTON, UNITED STATES
The Ship Canal Bridge is a heavily trafficked bridge over Portage Bay, a part of the Puget Sound, in Seattle, Washington. This bridge sees over 200,000 cars daily, which over time has contributed to significant 6PPD-quinone runoff into the bay. During frequent rainstorms, water flows over from the bridge, carrying tire particles containing 6PPD into the water below. Studies have identified 6PPD as the primary cause of pre-spawn mortality in coho salmon, which can die within a day of exposure to high toxin levels. A critical concern for researchers is whether 6PPD-quinone causes sublethal toxic effects in fish, which may be more challenging to detect than immediate death but could have profound implications for various aquatic organisms.
CRITICAL CASE: YUROK/HOOPA VALLEY
The Yurok Indian Reservation is the ancestral home of the Yurok Tribe, largest tribe in California with over 5,000 enrolled members (1). The reservation is in Del Norte and Humboldt counties of Northern California, along a 44-mile stretch of the Klamath River. (2) Like many Native American tribes in California and across the Pacific Northwest, the Yurok Tribe have complex and long-lasting cultural traditions tied to their ancestral land and its wildlife inhabitants, including the once abundant salmon population (1,3). The Klamath river has been a site of contestation since it was dammed in the early 1900s, which directly led to the dwindling of the Klamath salmon population which hatch in the river, live in the ocean for two or three years and then return to the river to spawn and die. This approach to land management had a devastating impact on indigenous communities throughout Northern California, undermining traditional ecological scientific knowledge and threatening indigenous food sovereignty.
Still, even after the Yurok regained some of their rights to manage their ancestral lands in the 1970s, the health of the river and its salmon population fluctuated wildly. In 2002, “the river was hit with a fish kill that wiped out over 34,000 adult salmon within just a few weeks. By 2005, they became officially endangered, after the population fell to as little as 1 percent of historic levels.” (4) In addition, in 2011, scientists reported a direct link between car tire dust, storm water runoff and salmon death that acutely affects coho salmon (6). Further study suggests other salmon species are also vulnerable to the toxic car tire dust (3).
As a result of indigenous activism and scientific research the Klamath River will be the site of the largest dam removal in world history which is scheduled to take place in 2023 and 2024 (5). In addition, in 2022, the California Department of Toxic Substances Control (DTSC) sought to designate the car tire chemical additive N-(1,3- dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) as a Priority Product (6, 7) in order to force manufacturers to remove the chemical from the California Market. This two-pronged approach is designed to restore the health of the river and its wildlife. For the Yurok Tribe it is an existential mission. “We’re salmon people,” says Samuel Gensaw of the Yurok Tribe. “Our whole life revolves around the relationship that we have with these salmon, because we believe that when these salmon disappear, we disappear” (8).
https://thecounter.org/yurok-tribe-klamath-river-salmon-fish-wars/