USTMA partnering to find 6PPD substitute

The U.S. Tire Manufacturers Association (USTMA) is partnering with government agency the United States Geological Survey (USGS) on a research project. The aim of this project is to assess and refine methods of evaluating potential alternatives to 6PPD, the antiozonant widely employed as a rubber stabilising additive when producing tyres.

Modern tyres contain 6PPD as the chemical serves critical safety and performance functions, protecting tyres from degradation upon exposure to ozone and oxygen in the air. Beyond that, it fulfils essential requirements for product durability and safety. This chemical innovation was initially conceived in the 1960s and has been an integral component of motor vehicle tyres since the 1970s.

This USTMA views its collaboration with USGS as an “important step in the continuing efforts by tyre manufacturers to look for possible 6PPD replacements.” Through its 6PPD Alternatives Analysis Consortium, USTMA is preparing a report to meet requirements under the California Safer Consumer Products regulation by March 2024.

Health hazard for fish

In 2020, a group of researchers published a paper that suggests 6PPD-quinone (6PPD-Q), a transformation product created when 6PPD interacts with ozone, is impacting the health of some fish species. Tyre wear through driving releases 6PPD-Q into the environment, with stormwater carrying the chemical into nearby rivers and streams.

“Every day, with every partner we can, USTMA is pushing forward in the industry’s effort to identify potential alternatives to 6PPD, and we recognise that additional research is necessary,” says Anne Forristall Luke, USTMA president and chief executive officer. “As USTMA continues its mission of advancing sustainability in the tyre industry, our work with USGS will break new scientific ground, benefitting the environment, communities, researchers, and manufacturers alike.”

An immediate alternative unlikely

In this study, USTMA and the USGS Western Fisheries Research Center are working together under a collaborative research and development agreement to establish a new method for in vitro toxicity testing of 6PPD alternatives. The study will expose fish cell lines to rubber containing three possible alternatives to 6PPD and their transformation products. Researchers will assess the toxicity of each proposed alternative and compare this to the toxicity levels of 6PPD-quinone. This methodology does not require testing on living fish.

While USTMA and USGS do not expect their initial research will immediately identify a 6PPD alternative, each of the three alternatives “represent a different class of chemical compounds” and “will inform future research.” The partners hope the results “will help future researchers narrow their focus as the search for an alternative continues.”

“The USGS is committed to working with federal, state, tribal, industry and other partners who share our scientific rigor to address this complex challenge,” says Michael Schmidt, director at the USGS Western Fisheries Research Center. “This joint research with USTMA is one important piece of our work aimed at filling top-priority knowledge gaps, not only on potential 6PPD alternatives, but also in how to evaluate them with brand new investigative methods.”

The partnership between USTMA and USGS is set to run through September 2024. The organisations expect initial toxicological results to be available in March 2024.