Formatted Title
Tire Wear Particles: A New Emerging Contaminant
Background/Objectives
Through the ongoing development of our understanding of microplastics, tire wear particles (TWPs) were recently identified as a specific source of microplastics to the environment. TWPs are a product of operating motor vehicles with tires made with synthetic rubber (e.g., synthetic rubber makes up 24% of a typical passenger vehicle tire). TWPs result from abrasion and are literally formed where the (synthetic) rubber meets the road. While TWPs can also be airborne particulate, the current focus is on their impact to surface water and aquatic life. TWPs enter surface water through stormwater runoff from roadways and other paved surfaces. 6PPD-quinone, a degradation product of the antioxidant and antiozonant rubber additive 6PPD, has been gaining specific attention as a critical chemical in TWPs since a 2021 study found it to be acutely toxic to certain species of fish.
Approach/Activities
The science is still nascent for TWPs and 6PPD-quinone, and potential regulations are uncertain in both scope and timeframe. In the interim, we should consider the adverse effects of unmitigated TWP discharge to surface waters. While most roadways where TWP runoff originates are not within the control of the private sector, there are decisions made by the private sector that affect the types of tires used, miles driven, and the speed of travel on public roadways. On private property, including driveways and parking lots, private industry controls the use of those paved surfaces and is responsible for managing the quality of stormwater runoff associated with them under a National Pollution Discharge Elimination System (NPDES) Permit. Today’s NPDES permits may adequately monitor TWPs via existing total suspended solids (TSS) requirements, but 6PPD-quinone is not monitored. We can, however, use the developing science to better understand the impacts to human health and the environment, sources, source control, mitigation, and treatment methods.
Results/Lessons Learned
While the path to regulating TWPs and 6PPD-quinone is unknown, we can take actions today to reduce their impact to stormwater runoff and surface water. Best management practices (BMPs) for stormwater management include diversion and grit (solids), oil removal, and the use of natural solutions such as vegetated areas to reduce solids and provide uptake of some dissolved contaminants. Current stormwater management features were not specifically designed to consider chemicals like 6PPD-quinone. We can take action today to enhance our stormwater BMPs to improve removal of TWPs and 6PPD-quinone while the science and regulations develop. Implementing proactive measures also facilitates achieving objectives under Environmental, Social, and Governance (ESG) programs that many companies have established that include reducing adverse effects on the environment from their operations and ensuring the sustainability of their business.