ITRC’s Tire Anti-Degradants (6PPD) Team will serve as a central location for shared information and coordination among states and Tribal Nations, as well as consolidate the limited available knowledge in this area, informing the public as to the science behind this problem, and efforts taken to minimize harm to aquatic life through the development of fact sheets and Online Training supplements.
Tire anti-degradants are used to extend the life of tires by preventing the cracking and breakdown of rubber as it reacts with ozone over time. 6 p-Phenylenediamine (6PPD) is currently the most prevalent chemical used for this purpose and is known to produce 6PPD-quinone (6PPD-q) through interaction with ozone. 6PPD and 6PPD-q enter the environment via tire fragments and particles on the road that eventually enters larger waterways and aquatic environments through runoff. In December 2020, researchers identified 6PPD-quinone (6PPD-q) as the second most toxic aquatic contaminant currently known. The presence of 6PPD-q in multiple media indicates the potential for exposure to a wide variety of aquatic organisms. There has been some research conducted on alternative anti-ozonants that can be used in tires as anti-degradants besides 6PPD. Other p-phenylenediamines (PPDs) have historically been used for this purpose, including IPPD, 7PPD, and 77PD. Many of these potential alternatives showed similar or superior performance in the lab as an anti-ozonant. However, 6PPD has emerged as the anti-ozonant of choice by the industry due to a wide variety of factors, including migration time, molecular weight, melting point, and compatibility with rubber formulations. This team will provide valuable information to states and the public, facilitate information gathering and sharing beyond the initial project scope, and may inform future projects related to 6PPD and tire-related contaminants.