Last November, CCKA submitted comments in support of the Department of Toxic Substances Control’s (DTSC) proposal to list potential chemical derivatives to ensure tire manufacturers evaluate and adopt safer alternatives to 6PPD, a chemical that poses a serious threat to salmon and aquatic ecosystems.
6PPD in Tires is Killing Salmon
For more than two decades, scientists have observed unexplained die-offs of salmon following rain events. For years, the specific pollutant causing these mass mortality events known as “urban runoff mortality syndrome” remained unknown.
In 2020, researchers finally identified the cause: a chemical found in nearly all motor vehicle tires – 6PPD-quinone. 6PPD is an anti-degradant that reacts with oxygen and ozone to protect car tires from cracking. While 6PPD effectively prevents tires from cracking, its byproduct is extremely toxic to fish – so toxic that the U.S. Environmental Protection Agency has identified it as the second most toxic chemical ever tested for aquatic species.
When rain washes 6PPD-quinone off roadways and into streams, it kills salmon almost instantaneously. Coho salmon, an endangered keystone species essential to California’s ecosystems and of significant importance to tribes, are especially vulnerable.
Dangerous Substitutes Could Replace 6PPD
In 2023, DTSC officially listed motor vehicle tires containing 6PPD as a “Priority Product” under the Safer Consumer Products Program. This designation requires tire manufacturers to conduct Alternatives Analyses to identify and assess potential substitutes.
However, many of the replacement chemicals identified by tire manufacturers so far are other PPD derivatives – chemicals that are structurally and functionally similar to 6PPD. Preliminary data suggest that several of these derivatives exhibit comparable toxicity to aquatic life. In other words, without careful regulatory oversight, manufacturers could replace 6PPD with another PPD compound that poses similar, devastating ecological risks.
Listing PPD derivatives as “Candidate Chemicals” will help prevent this outcome. The listing ensures that any proposed PPD substitute for 6PPD will be evaluated for its environmental and toxicological impacts before use. This proactive measure aligns with the Safer Consumer Products Program’s mission to reduce harmful chemicals in consumer products through safer design and innovation.
Why This Matters
Salmon are a keystone species, essential to the health of California’s rivers and ecosystems. They are also of significant cultural and spiritual importance to Tribes in California, supporting tribal subsistence as well as traditional and ceremonial practices.
The collapse of salmon populations has far-reaching ecological, cultural, and economic consequences. Protecting salmon from toxic runoff is critical to safeguarding California’s waters, fisheries, and communities.
CCKA’s Position
CCKA supports DTSC’s proposal to list PPD derivatives as Candidate Chemicals under the Safer Consumer Products Program because this action will:
- Help prevent harmful substitutions that replicate the hazards of 6PPD;
- Promote safer chemical innovation within the tire industry; and
- Support the protection of California’s waters from tire-related chemical pollution.
Looking Ahead
CCKA will continue to engage with DTSC and stakeholders to promote:
- Full evaluation of tire antioxidant alternatives under the Safer Consumer Products Program;
- Research and innovation in safer tire materials; and
- Policies that protect the health of California’s waters and communities.
Through these efforts, California can be a leader in addressing tire-related pollution and ensuring that our waters remain fishable, swimmable, and drinkable for generations to come.
Staff Attorney Marty Farrell advocates for statewide policies and programs that protect the health of California’s water.
