Recent research findings identified 6PPD-quinone as the major agent responsible for exceptionally high levels of rapid mortality of adult Coho salmon in some urban streams. Lethal effects occurred in Coho at very low concentrations of 6PPD-quinone. Related studies have found the chemical is also toxic to rainbow trout, and King Salmon, and other aquatic species may be at risk as well. So far, the lethal impact, presumably from 6PPD-quinone, has only been documented in urban streams that receive runoff from high average daily traffic (ADT) highways.

6PPD is a chemical added to tires to increase their life by reducing tire oxidation. It has been used for over 40 years in almost all tires and is assumed to be ubiquitous in roadway runoff, as are tire particulates that have been detected in fish across the country. Potential sources of 6PPD-quinone in stormwater include tire wear particulates, abrasion of pavement that contains tire derived aggregate (TDA), and potentially leachate from fill incorporating ground tires. Although standard analytical test methods are not yet available, researchers have detected 6PPD and linked it to toxicity in runoff; standard methods are currently under development by the WA Department of Ecology.

Questions of importance for DOTs are: 1) Under what conditions and where is 6PPD-quinone related toxicity an issue, 2) what highway related and receiving water factors are implicated, and 3) what drainage characteristics and stormwater management techniques are capable of reducing or eliminating the toxicity of highway runoff due to 6PPD-quinone and other pollutants (zinc, copper, PAHs, etc.).

There are also concerns about use of TDAs in the roadway environment. DOTs and other transportation agencies will be a primary target of regulatory efforts to address 6PPD-quinone toxicity. Projects have already been delayed due to uncertainty as to where, what type, and how much treatment of roadway runoff is necessary.

The research, identified as a priority for a Research Needs Statement by the TRB AKD50 Stormwater Subcommittee, will 1) identify where and what features within the highway environment contribute acutely toxic runoff associated with 6PPD-quonine and 2) identify and develop practical treatment facilities and stormwater management approaches that can be used in urban and rural areas.

The objective of this research is to identify under what conditions runoff intervention is needed and develop and provide design guidance for stormwater treatment and management techniques that substantially reduce or eliminate highway runoff toxicity, as well as 6PPD-quinone specifically. Toxicity testing is vital because there is no formal toxicity criteria for 6PPD-quonine, and other components of highway runoff likely affect toxicity as well.

Major tasks or activities:
• Literature review on 1) highway runoff toxicity, with an emphasis on 6PPD-quinone toxicity and 2) effectiveness of treatment and stormwater management, including the effect of vegetated drainage system types on toxicity reduction.
• Field collection of highway runoff and laboratory analyses to:
i. Assess toxicity reduction of high traffic highway runoff routed through bare soil, compost amended soil and vegetated conveyances
ii. Design and conduct a laboratory study to determine filtration material characteristics and mechanisms (such as layer thickness, infiltration rate, contact times, etc.) necessary for effective toxicity and/or 6PPD-quinone concentration reduction by BMPs
iii. Conduct selected 6PPD-quinone leachability tests for tire derived aggregate/crumb rubber containing pavement materials
• Identify the components and features of the highway system and receiving waters that affect 6PPD-quinone toxicity and its impacts.

Deliverables:
• A report that provides 1) guidance on identifying situations where 6PPD-quinone targeted BMPs are appropriate to avoid toxic impacts, 2) an initial assessment of the potential for TDAs to contribute to toxicity, and 3) design criteria for 6PPD-quinone targeting BMPs. Research documenting toxicity reductions by drainage systems and BMPs etc. should be prepared for peer reviewed publication.