So far, a more environmentally-friendly alternative to keep tire rubber from degrading hasn’t emerged.

By Bill Lucia, Washington State Standard, August 1, 2023

Two tribes in Washington are asking federal regulators to ban a chemical widely used in car tires that scientists have identified as highly toxic to salmon and other fish.

The Port Gamble S’Klallam and Puyallup tribes, along with the Yurok, which is the largest native nation in California, petitioned the U.S. Environmental Protection Agency on Tuesday to establish regulations prohibiting the manufacture and use of the substance, known as 6PPD.

Researchers in 2020 identified an offshoot of the chemical–6PPD-quinone, or 6PPD-q–as the culprit causing premature salmon deaths in urban streams and rivers in the Puget Sound region.

Manufacturers, dating back to around the 1950s or 1960s, have used 6PPD as a preservative to keep tire rubber from cracking and degrading. But when the chemical reacts with ozone in the atmosphere, it yields 6PPD-q. The substance ends up on roads and other surfaces as tires wear and from there, it gets washed into streams and other bodies of water that provide salmon habitat.

“To see 6PPD-q kill the salmon that are reared in the Port Gamble S’Klallam Tribe’s own streams and from its own hatchery is an unconscionable slap in the face to a people who rely on salmon for their wellbeing, in addition to being a gross violation of the Tribe’s rights as enshrined in the 1855 Treaty of Point No Point,” Josh Carter, the tribe’s environmental scientist, said in a statement.

The environmental group Earthjustice submitted the petition on behalf of the tribes. “There is no known safe level of 6PPD in tires, and no warning or label requirements will eliminate the unreasonable risk from the use of tires containing 6PPD,” the filing says.

The U.S. Tire Manufacturers Association said it was reviewing the petition and that its members are already evaluating possible 6PPD alternatives.

“We have actively aligned with numerous federal and state regulatory bodies, including Washington state researchers and regulators, material suppliers, academic and government research teams, industry associations and other partners to advance research into 6PPD-Quinone and identify effective mitigation strategies,” the group said in an email.

“Tires are one of the most important safety components of a car and 6PPD serves a critical safety purpose in a tire,” the association added. 

So far, no straightforward fix to 6PPD contamination has emerged. Even environmental regulators, like Washington’s Department of Ecology, acknowledge the chemical has safety benefits by preventing tires from breaking down and reducing the number of used tires disposed of in landfills.

Ecology has a slate of initiatives underway to better measure pollution from 6PPD-q, to cut the amount that ends up in the state’s waterways, and to find safer alternatives.

In the current budget cycle, the state Legislature 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.

California last week adopted a rule that requires makers of motor vehicle tires for sale in the state to evaluate safer alternatives to 6PPD.

“We are working with the U.S. EPA, other states, researchers and the Tire Manufacturers Association to find a path to make tires safer for our environment without compromising on-road safety,” Meredith Williams, director of California’s Department of Toxic Substances Control said last week.

The tire manufacturers group says it has “mobilized” a consortium of 16 tire manufacturers to conduct an alternatives analysis for 6PPD in tires under California’s Safer Consumer Product Regulations.

The petition from the tribes describes 6PPD-q as the “second most toxic chemical to aquatic species ever evaluated by EPA” and cites research indicating it can kill coho salmon within hours. It also notes how traces of the chemical are showing up not just in stormwater runoff and urban watersheds, but also in household dust and even human urine.

“It is time for the EPA to phase out this highly toxic chemical,” Elizabeth Forsyth, a senior attorney with Earthjustice’s Biodiversity Defense Program, said in a statement.

Studies have shown that the chemical not only harms salmon but also other species, like various types of trout and char.

Franji Mayes, an Ecology spokesperson, explained in an email that the agency does not have the authority to impose a ban or phase-out chemicals in consumer products unless it determines safer alternatives are feasible to use and available. In a 2021 technical memo, the agency identified potential alternatives to 6PPD and noted the need for further research.

“We are currently funding research to help us learn more about what chemicals to include in the alternatives assessment and to fill data gaps around these chemicals,” Mayes added. “As we receive the results of this research, we will be able to establish a more firm timeline for our alternatives assessment.”

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