Measuring 6PPD-q: Developing Methodologies and Best Practices

6PPD-quinone (6PPD-q) is a degradation product of a preservative (6PPD) used in automobile tires since the 1970’s. In 2020, it was discovered that 6PPD-q is acutely toxic to coho salmon and, to a lesser degree, several other aquatic species. Freshwater coho habitat in the United States ranges from the tip of the Aleutian Islands to Santa Cruz. To protect this important species and other aquatic life, environmental managers need more knowledge on the levels of 6PPD-q found in highway runoff and how effective modern stormwater technologies are at removing 6PPD-q. Additionally, we need to establish best practices for collecting composite stormwater samples for 6PPD-q analysis.  

In 2023, in partnership with the Washington State Department of Ecology and the King County Environmental Laboratory, Herrera conducted a first of its kind study examining (1) the 6PPD-q removal effectiveness of proprietary high flow rate stormwater treatment technologies, and (2) if and how much stormwater sampling equipment (e.g., tubing and bottle materials) and protocol affects the measured concentration of 6PPD-q.  

Our findings agreed with the growing body of evidence that biologically active soil media provides superior removal of 6PPD-q, with one of the technologies (a high flow rate biofilter) providing up to 98 percent reduction, while other technologies (e.g., membrane filter, cartridge filter) provided reductions of only 25 to 50 percent.  

We also found that some sampling equipment and protocols had a measurable effect on 6PPD-q recovery in highway runoff. However, these losses (or gains) are within typical measurement quality objectives for environmental studies. Additionally, we found detectable levels of 6PPD-q in our field equipment blanks. These impacts may be more profound at low levels of 6PPD-q, such as in receiving waters.   

Herrera is proud to support insights into how current collection methods contribute to the understanding of 6PPD-q. The challenges of mitigating future harm and restoring ecosystems from previous damage are resolved using solutions that are rooted in our current understanding and are built on the findings of our peers. It is only together, across disciplines, that we will be able to restore our valuable coho fisheries.

Contributor: Dylan Ahearn, PhD