USTMA Statement on California DTSC’s Actions Regarding Zinc and 6PPD in Automobile Tires

The U.S. Tire Manufacturers Association (USTMA) today issued the following statement in response to the California Department of Toxic Substances Control (DTSC) announcement that a petition to review zinc in automobile tires under the state’s Safer Consumer Products Regulations has been granted:

The decision to grant a petition to add vehicle tires containing zinc oxide to the California Safer Consumer Products Regulations Priority Products list will not achieve its intended purpose.  However, we support DTSC’s decision to include discussions about 6PPD in future workshops and we support designating 6PPD in automobile tires as a Priority Product for review under the state’s green chemistry program.

Zinc
 Zinc is found naturally in the environment and is contained in many products including galvanized metal, fertilizer, paint, batteries, brake pads and tires.  Research demonstrates that discharges of domestic wastewater and galvanized metal surfaces account for 75% of zinc in the environment, while tires typically account for less than 10%.

Because zinc is widely used in many products, zinc water quality issues can only effectively be mitigated through a collaborative, holistic approach. Since 2016, USTMA has worked with the California State Water Resources Control Board, the International Zinc Association, and the California Stormwater Quality Association as part of a collaborative process to identify effective solutions to zinc water quality issues in the state.  USTMA continues to believe that this effort is the most promising avenue to resolve California’s zinc water quality issues, and we urged DTSC to support this collaboration before moving to a narrow focus on zinc in tires under the Safer Consumer Products regulation.

Zinc oxide plays a critical and irreplaceable role in manufacturing tires. Zinc oxide serves as an “activator” in the vulcanization process that turns soft, sticky rubber into stable components that allow a tire to carry the weight of a vehicle and to stop safely. Manufacturers have tested a variety of other metal oxides to replace or reduce the use of zinc but have not found a safer alternative. Without the use of zinc oxide, tires cannot meet federal safety standards.

6PPD
Tire manufacturers recommended adding 6PPD to the Priority Products Work Plan following a recent study that suggests a link between Coho salmon mortality and a transformation product of 6PPD from tire and road wear particles (TRWP) called 6PPD-quinone. The tire industry uses 6PPD to help tires resist degradation and cracking, which is vital for passenger safety. 6PPD has been studied, but not enough is known about the newly discovered transformation product, 6PPD-quinone. We are committed to collaborating with researchers and regulators in California and Washington to better understand this material, fill knowledge gaps and determine next steps.

Tire manufacturers’ commitment to sustainability
Tire manufacturers are dedicated to understanding and reducing the environmental impact of their products. USTMA members — both individually and through partnerships — are working to incorporate more renewable and recycled materials into tires, enhancing biodiversity and reducing dependence on non-renewable feedstocks. Cooper, Goodyear, Pirelli, and Continental are working with academic institutions and other partners to explore the use of dandelions as an alternative to rubber. Bridgestone, Goodyear, Yokohama and Hankook are replacing petroleum in tires with vegetable, soybean or orange peel oil.

We intend to continue advancing this commitment to sustainability through collaboration with the California State Water Resources Control Board and California Stormwater Quality Association to help find effective solutions to the state’s zinc-related water quality issues.