The objective of this Statement of Need (SON) is to solicit innovative research that leads to a better understanding of the environmental fate and transport of chemicals released from tires and tire wear particles (TWP). Of particular interest is the transformation product, 2-anilo-5-[(4-methylpentan-2-yl)amino]cyclohexa-2,5-diene-1,4-dione (6PPD-quinone), which has been implicated in toxicity to coho salmon (Oncorhynchus kisutch) and other salmonids at environmentally relevant concentrations. This work should focus specifically on 6PPD-quinone and its parent compound, 6PPD, but can include other known tire-derived organic pollutants (TDOPs) such as other p-phenylenediamine derivatives, N,N-dicyclohexylmethylamine (DCA), or 1-cyclohexyl-3-phenylurea (CPU).  

The proposed work should include studies on the physical-chemical properties, transport, and transformation of chemicals released from tires to predict their behavior within various environmental systems, engineered treatment systems, and biota. Specific research interests include the following: 

• Develop improved physical-chemical properties of TDOPs such as vapor pressure, solubility, Henry’s Law constant, K_OW, K_OC, diffusivity in tire rubber, and pK_a, with a focus on clarifying discrepancies in literature-reported properties of 6PPD and its transformation product, 6PPD-quinone.
• Investigate how TDOPs in the environment move through urban runoff, soils, sediments, and wastewater systems. This includes understanding the size distribution and deposition of TWPs, generation of TDOPs, partitioning between dissolved and particulate phases (including tire rubber), and their affinity for organic carbon and relevant ion exchange sites on minerals.
• Improve the fundamental understanding of the environmental persistence of TDOPs by evaluating degradation rates under varying natural conditions, such as temperature, pH, light exposure, and microbial activity.
• Characterize abiotic transformation mechanisms such as ozone oxidation, UV photolysis, and metal-catalyzed reactions (e.g., Fe³⁺, Cu²⁺), and identify intermediate products and their persistence.
• Assess the environmental half-lives of 6PPD and 6PPD-quinone in water, soils, sediment, and on road surfaces to better predict their fate and inform risk assessments under environmentally relevant conditions. 

Proposers must provide a clear rationale and justification for all study parameters, including proposed methods for generating and characterizing TWPs, target compounds, and environmental media. For analytical work, performers must demonstrate their ability to analyze 6PPD-quinone in accordance with EPA Draft Method 1634 and the ability to meet the requirements outlined in Module 4 of the Environmental Data Quality Workgroup Quality Systems Manuals v 6.0.  

Improved understanding of the potential environmental risk of chemicals released from tires and TWPs to the aquatic environment will assist in the development of appropriate site-specific risk assessments and decisions related to mitigation of exposures at these sites. In addition, improved understanding of how chemicals released from TWP partitions between various environmental media will allow refinement of site conceptual models used in focused risk assessments. 

6PPD-quinone is a transformation product of 6PPD, the primary anti-degradant added to tires and used to prevent premature weathering and degradation of the rubber from sunlight, oxygen, and ozone damage. Multiple studies have identified 6PPD-quinone in stormwater-impacted streams at concentrations that are acutely toxic to fish and other aquatic organisms. Developing an improved understanding of this compound—alongside other quinones and tire rubber antioxidants—is of interest to better understand the impact to stormwater runoff. 

The cost and time to meet the requirements of this SON are at the discretion of the proposer. Two options are available: 

Standard Proposals: These proposals describe a complete research effort. The proposer should incorporate the appropriate time, schedule, and cost requirements to accomplish the scope of work proposed. SERDP projects normally run from two to five years in length and vary considerably in cost consistent with the scope of the effort.  

Limited Scope Proposals: Proposers with innovative approaches to the SON that entail high technical risk or have minimal supporting data may submit a Limited Scope Proposal for funding up to $350,000 and approximately one year in duration. Such proposals may be eligible for follow-on funding if they result in a successful initial project. The objective of these proposals should be to acquire the data necessary to demonstrate proof-of-concept or reduction of risk that will lead to development of a future Standard Proposal. Proposers should submit Limited Scope Proposals in accordance with the SERDP Core Solicitation instructions and deadlines.