Where the

Meets the


to Address Tire

Wear Particles
In Waterways





APRIL 2023

U.S. Environmental Protection Agency

Office of Wetlands, Oceans and Watersheds
Trash Free Waters Program

Photo credit: Lonny Meyer/Courtesy of Estuary News


The mission of the US Environmental Protection Agency's (EPA's) Trash Free Waters program
("TFW") is to prevent trash from getting into our waterways and remove trash that is already in
the environment. TFW works to improve the health of our nation's waterways and communities
by fostering effective partnerships, providing informational resources, and facilitating shared
learning. Microplastics, including tire wear particles, are part of the program's purview. Tire
wear particles are small, plastic particles primarily generated by abrasion with pavement. They
enter the aquatic environment in roadway runoff. Recent scientific studies suggest that tire wear
particles, and contaminants associated with the particles, can potentially harm aquatic life (see,
for example, Tian et al. 2021 finding that 6PPD quinone, a tire rubber-derived chemical, induces
acute mortality in coho salmon). The extent to which tire wear particles may impact human
health via ingestion and other processes is unknown.

EPA's TFW Report on Priority Microplastics Research Needs: Update to the 2017 Microplastics
Expert Workshop (2021) identified tire wear particles as an area of increasing focus in the
research community. Tire wear particles as a pollutant in waterways is a relatively new field of
study without standardized terminology, assessment methodologies, or established solutions. The
emergence of tire wear particles as a specific microplastics concern prompted EPA to convene
stakeholders in two roundtable discussions in Spring 2022 to facilitate shared learning about the
challenges of addressing the problem of tire wear particle pollution. The roundtables focused on
the issue of tire wear particles generated by vehicles driving on roadways.1 Stakeholders
represented diverse perspectives on the nature of the problem and how to effectively address it.
Appendix A contains a list of participating organizations.

The roundtables provided a forum for discussion among participants without committing to a
specific course of action. Participants discussed a set of questions aimed at understanding the
barriers to and opportunities for managing tire wear particles in waterways. The questions

•	Where are the barriers to managing tire wear particles in roadways and waterways?

•	What specific opportunities could improve awareness and management of the problem?

•	What information, data, or tools could help your organization better address this issue?

•	What specific roles or products should EPA initiate to address tire wear particle issues?

This brief report summarizes the roundtable discussions. In producing it, EPA seeks to make
public the challenges and potential solutions discussed during the roundtables, in order to
broaden the community engaged in addressing tire wear particle pollution. The report begins
with a short primer on tire wear particle pollution before introducing the challenges and potential
solutions identified by the roundtable participants.

1 The roundtable discussions did not address tire wear particles sourced from recycled tire crumb rubber, often
used in applications such as sports fields or playgrounds.



Vehicle tires are made of a variety of components designed to support longevity and
performance. The ability of a tire to grip the pavement is critical for the safety of vehicular
travel. However, the contact between tires and road surfaces causes abrasion of both the tire and
road surface, resulting in deposition of particles on or near roadways that then become part of
stormwater runoff into local waterbodies, or are emitted into the atmosphere as dust that contains
tire wear particles (see, for example, Brahney et al. 2021, Baensch-Baltruschat et al. 2020,
Baensch-Baltruschat et al. 2021). Recent studies have found that tire wear particles comprise
approximately 85% of the microplastics identified in waterways (Werbowski et al. 2021).

Kole et al (2017) estimated the global average tire wear particles emissions per capita at 0.81
kg/year, with per capita emissions in the USA estimated at 4.7 kg/year. According to the U.S.
Tire Manufacturers Association, record tire shipments of more than 340 million units were
predicted for the U.S. market for 2022, which is about 5 million more tires than in 2021 and 8
million more than in 2019.2

Researchers are unravelling the complexities of how particles are generated. For example, the
number of particles generated depends on tire composition, driving speed and style, road surface
type and condition, temperature, and other factors. Researchers report that the majority of tire
wear particles are conglomerates of tire and road wear particles due to the interaction of tires
with pavement and can vary in size from 1 nanometer to 5 millimeters (Kole et al. 2017, Wagner
et al. 2018). The presence of recycled tire crumb rubber in certain pavement complicates source
evaluation (i.e., from the roadway itself, tires, or a combination). Due to a lack of standardized
detection, collection, and quantification methods for these small particles (primarily <100 |im),
the quantity of tire wear particles is likely underestimated in aquatic environments.

Tires include components such as antioxidants, antiozonants, and curing systems to enable safe
and effective performance.3 Specific tire formulations vary across tire types, manufacturers, and
countries. Therefore, tire wear particles have variable chemical compositions (Chibwe et al.

There is concern that degradation of tire wear particles can release chemicals from these
components with the potential to pose ecological and health risks. In addition, tire wear particles
may provide attachment surfaces for biotic and abiotic pollutants, and therefore become a source
of these pollutants in roadway runoff to local water bodies (Luo et al. 2021, Wang et al. 2020).
Many questions remain regarding the ecological risks of exposure to tire wear particles.


The roundtable participants shared the challenges they face in addressing the issue of tire wear
particles in waterways and also brainstormed potential solutions and tools to address the
identified challenges. Stakeholders made specific recommendations within the general categories
of research, funding, education, and coordination. The participants also suggested engagement

2	U.S. Tire Manufacturers Association, www.ustires.org/2022-tire-shipment-outlook

3	U.S. Tire Manufacturers Association, http://www.ustires.org/innovation.


opportunities for EPA. Some participants shared information about ongoing research and related
efforts. These are presented in Appendix B.

Table 1 provides a high-level summary of the challenges and potential solutions to addressing
tire wear particles in waterways. The narrative following the table presents the substance of the
discussions more fully, though no direct comments or attributions are included. The discussions
reflected a range of organizational perspectives and geographic locations, which informed the
approaches, tools, and research suggested as solutions.






Research:	• Lack of information on the physical

Measurement	and chemical characteristics of tire

and Effects	wear particles, and their transport,

fate, and ecological and human health

•	Lack of information on abrasion rates
and influencing factors.

•	Lack of standardized methods for
collecting, separating, and quantifying
tire wear particle pollution, and
studying the impact on waterways.

•	Access to necessary instrumentation
for testing and analysis.

Collaborate on studies that investigate the
physical and chemical characteristics of tire
wear particles, and transport, fate, and
ecological and human health effects.
Collaborate on studies designed to further
the understanding tire abrasion.

Develop and validate collection, separation,
and quantification methodologies.

Create a clearinghouse of available data and
research to encourage information sharing.


Lack of information on alternative tire
and pavement designs that meet safety

Lack of information on available
stormwater treatment options and
testing results on their effectiveness.
Identify land availability and locations
to install stormwater treatment

Coordinate research programs on

alternative tire and pavement designs that

meet safety requirements.

Develop EPA guidance to help states and

municipalities manage tire wear particles

(e.g., using stormwater best management

practices) as an interim solution while long-

term strategies are developed.

Compile information and case studies on

tire wear particle reduction, capture, and

treatment solutions, including information

on cost and efficacy.

Could use existing tools to identify

appropriate locations for stormwater

treatment installation

Provide industry with incentives to develop

and test alternative tire designs.





Costs and

High cost of research to collect, test,
and monitor particle shedding, and
understand ecological and human
health effects.

High cost of development and testing
of treatment options and other

Conduct cost-benefit analyses of various
solution options.

Model the effectiveness of various solutions
to inform priorities.

EPA could provide guidance on research,
treatment, and other priorities to ensure
that funding is used effectively.

Involve stormwater utilities in discussions
about particle capture including green
stormwater infrastructure solutions.


Lack of consumer education on the
generation of tire wear particles, and
their role in reducing or mitigating
particle generation.

Lack of incentives for consumers to
adopt best practices for reducing tire
wear particles.

Conduct national, state, Tribal, or local

Raise public awareness with messages about
how tire abrasion generates tire wear

Compile best practices for reducing tire
wear particles and other information in a
public clearinghouse.

Coordination • Lack of government leadership and
coordination undermines advances.
• Lack of coordinated response
disproportionately impacts Tribes.

EPA and other governmental entities should
provide leadership and coordinate mitigation
and research efforts.

Include national, Tribal, state, and local
governments in continued coordination.
Provide incentives for reducing miles
traveled in coordination with other
transportation programs.


Roundtable participants generally agreed there is a lack of information on the physical and
chemical characteristics of tire wear particles and the impact of these particles on human and
environmental health. For example, research is needed to determine which chemicals are
released from tire wear particles into stormwater and receiving waterbodies, and what effects the
particles and their associated chemicals have on aquatic life and human health.

Tires are complex and diverse in chemical composition and how they wear on the road.
Participants identified data needs, including determining the percent of particles that fall into
various size fractions, identifying the vehicle classes with the highest rates of tire wear particle
emissions, and finding less ecologically impactful tire substitutions that meet performance,
quality, and safety standards.

Because tire abrasion results from the grip between tires and the road, tire safety was described
as a critical consideration before making a change to tire or road design and/or composition.
Many factors influence abrasion rates, including tire design, vehicle weight, distribution of the
vehicle load, location of the driving wheel, tire maintenance, road surfaces, and weather.
Participants suggested focusing research on determining abrasion rates, which could inform
future controls, surveillance, or regulation regarding tire wear particles.


Participants noted that many scientists do not have the instrumentation needed to characterize
tire wear particles, particularly at the nano-scale. Scientific literature on the transport of tire wear
particles and associated chemicals is sparse, but this information is necessary to effectively
manage tire wear particles and minimize their impacts in waterways. Environmental monitoring
of particles in air and surface water runoff would provide needed information. Indeed, much of
the roundtable discussions focused on the importance of standardized tire wear particle
collection, separation, and quantification methodologies and analytical approaches to studying
the impacts of tire wear particles on waterways. Generally, participants agreed that a
standardized methodology for collection, separation, and quantification of particles or validation
of existing methods would better enable future tire wear particle research and mitigation efforts.
Consistent methods and access to laboratory instrumentation will be critical for the successful
collection and analysis of tire wear particles. In addition, there was agreement on the importance
of understanding tire wear particle composition, fate, and transport, as well as awareness of how
relevant factors (e.g., tire use and safety) impact decision-making about which solutions to

Participants suggested collaboration among scientists, industry, and state, Tribal, and federal
agencies (both environmental and transportation) would be a helpful next step. Several
participants proposed a clearinghouse of available data on tire wear particle size, composition,
fate and transport, and impacts to encourage coordination and information sharing among
research organizations.


A recurring theme was the lack of a one-size-fits-all approach to tire wear particle reduction,
capture, and treatment. One participant described a framework developed by the San Francisco
Estuary Institute that integrates a broad array of potential solutions that merit further
investigation (Moran et al. 2021; Johannesson & Lithner 2022). The framework is structured as a
continuum of solutions from prevention of tire wear particle formation to remediation of the
resulting pollution. Examples of the solutions described in the framework include:

•	Prevention actions by tire or vehicle manufacturers. These include product reformulation,
voluntary tire ingredient review systems, or voluntary product ingredient controls.

•	Reduction actions, including development and adoption of a reduced tire abrasion rate
standard, production of airless tires, and/or inclusion of tire pressure monitors on all
vehicles to reduce tire wear debris formation. Other ways to reduce debris could involve
modifying road surfaces to reduce wear, reducing vehicle miles traveled, and changing
driver behaviors.

•	Remediation actions to treat the tire wear particle pollution. Techniques to remove tire
wear particles and/or associated chemicals from surface water runoff include bioretention
to treat runoff, infiltration (if safe), and diversion of "first flush" runoff to wastewater
treatment plants.

The framework prompted discussions about prevention actions, including tire modification and
development of new vehicle designs. Some participants suggested that research focus on
technology and innovation to reimagine tires to use different materials and fewer toxic
chemicals, or to design tire wear particle capture systems for use on vehicles. A participant
mentioned that efforts are underway to develop tire wear particle collection systems for


installation on vehicles. Research on alternative tire design, such as airless tires that wear less
than traditional tires, is ongoing. However, more research is needed to ensure that any alternative
designs maintain the safety, durability, and other critical factors that traditional tires provide to
meet regulatory requirements on safety. In addition, future vehicle designs should also consider
the impact on tire wear particle generation and how vehicle improvements may be able to
address the issue. For example, electric vehicles are hailed for their ability to reduce air pollution
and emissions but may generate more tire wear particles than traditional gasoline-powered
vehicles due to their increased weight. In the case of self-driving vehicles, they could be
programmed to reduce tire wear with appropriate braking. Participants encouraged the
development of incentives for industry to research and develop tires that are less prone to
abrasion or vehicles that reduce tire wear or even vehicles without tires.

Participants also discussed approaches for reducing the generation of tire wear particles. One
topic to explore is the availability of pavement alternatives that may reduce tire abrasion. In
addition, a participant suggested investigating whether recycled tire materials used in asphalt
resurfacing contribute to tire wear particles in waterways. Participants suggested coordination
among research programs on alternative tire and pavement designs that meet safety

In the area of remediation of tire wear particle pollution, the participants requested EPA
guidance to help states and municipalities manage tire wear particles while long-term solutions
are developed. Such guidance might include stormwater best management practices and green
infrastructure designs to capture tire wear particle pollution. Advancements in particle capture
technology, such as catch basin inserts or filters to stop trash from moving from roads into
stormwater conveyances, could be amended to address tire wear particles. One participant
suggested the small size of tire wear particles is a barrier to collecting them, and that filter
technologies deployed to collect tire wear particles from roadways could be developed. Certain
green infrastructure techniques, such as bioretention areas, have potential for capturing tire wear
particles before they reach waterways. Participants noted that further examination of stormwater
management practices to evaluate efficacy and feasibility for collecting tire wear particles is
needed. Solution design and selection should consider both the relevant tire particle size (e.g.,
nanoparticles to about 100 |im) and surface area.

There was consensus that communities could not just "treat their way out of' the tire wear
particle problem. Land availability is another barrier noted. Most green infrastructure and
stormwater management practices require space, which might not be available near roadways or
adjacent to downstream waterways. Participants advocated that stakeholders compile information
on the testing, feasibility, and practicality of tire wear particle capture solutions to help decision-
makers understand the efficacy and applicability of stormwater remediation options.


When discussing the barriers to understand tire wear particle toxicity and treatment options,
roundtable participants identified costs as a major issue. Costs are associated with research to
collect, test, and monitor particles shed from tires, to understand the ecological and human health
effects of exposure to tire wear particles, and to develop and test treatment options and
alternatives. Future discussions involving prevention through particle capture should involve
entities administering local stormwater utilities and consider funding green infrastructure
solutions where such practices are not already eligible for funding.


Participants also noted that not addressing the problem could lead to significant costs. The
"downstream" costs of what happens to the environment and human health could be considered
in a cost-benefit analysis, including costs to indigenous and at-risk communities. It was noted
that Tribes are discussing the legal ramifications of the loss of food sources (such as salmon or
other fish) resulting from the effects of tire wear
particle pollution on ecosystems. Without
meaningful improvements in mitigating tire
wear particle generation and impacts to water-
bodies, this could result in litigation costs to the
Tribes and potential defendants (e.g., states).

To ensure that funding is used effectively,
participants suggested it would be helpful for
EPA to develop guidance on research,
treatment, and other priorities. For example,
participants discussed that modeling potential
solutions may determine their effectiveness,
which could then inform a roadmap for future
mitigation. Modeling the relative effectiveness
of various interventions (e.g., reduction in miles
driven, substitution of low abrasion tires, green
infrastructure, etc.) could help decision-makers
prioritize interventions with the potential for the
greatest reductions in tire wear particle


Participants acknowledged that consumers could play a role in reducing tire wear by changing
the ways they operate their vehicles. However, most consumers are not aware of how their
driving habits affect the generation of tire wear particles, or even that tire wear particle pollution
is an environmental issue. Educational materials should include clear definitions of terms such as
abrasion and microplastics, as well as explanations for how driving behavior influences the
generation of tire wear particles. For example, both tire inflation and driving style (e.g., hard
stops and starts) are something that drivers control, but consumers will need to understand not
only how to change their behavior, but why such changes would be helpful in reducing tire wear
particle pollution. By eliminating unnecessary trips to reduce vehicle miles traveled, consumers
could be part of the solution. As with any suggested change in consumer behavior, providing
educational resources and incentives for modifying habits will be necessary to support public
adoption of best practices for reducing tire wear particles.

Raising awareness about the factors that cause tire abrasion and what happens when tire wear
particles reach waterbodies was identified as the first step in educating the public. Participants
recommended providing the public with information on the proper inflation of their tires and
how their driving techniques can reduce tire abrasion. A participant noted that some education
efforts are already underway, such as a regional stormwater outreach group in the Seattle area
that focused on auto maintenance, eco-driving practices, and a study on 6PPD-quinone in street
sweeping waste. Awareness and education could take place at the national, Tribal, state, and







local level, and participants noted that national coordination or tools would help create a
consistent message.

Education was also mentioned as a way to help stakeholders across the country understand if,
and to what extent, pollution from tire wear particles is a locally important issue, including on
Tribal lands and in communities with environmental justice concerns. Digital compilations of
research, alternatives, best practices, and other critical information in one easy-to-access public
clearinghouse was a common request during the roundtables.


Because tire wear particle pollution is an issue at the local, state, and national scales, participants
acknowledged that it would take leadership, coordination, and political will to comprehensively
address and mitigate the generation of tire wear particles and their effects on waterways.
Consistent definitions, methods, thresholds, incentives, and requirements are necessary to ensure
the success of all remediation and mitigation efforts, as is clear leadership. Roundtable
participants sought leadership from EPA on scientific methodologies, measurement, research
funding, prioritization, information gathering, best management practices, and education. In
addition, they suggested the U.S. Department of Transportation (DOT), state agencies with
authorities relevant to any aspect of the tire wear particle issue, and local stormwater utilities also
have roles to play. State agencies sought a more developed understanding of the types of efforts
their communities plan to pursue, so they can seek funding for such projects. State DOTs,
regional transportation authorities, and municipal governments could also provide incentives and
alternatives to decrease vehicle miles traveled and increase walkability to reduce the generation
of tire wear particles on busy roads. Intergovernmental coordination related to tire wear particle
remediation and mitigation must include Tribal governments, as Tribal communities are
guaranteed fishing access in many waterbodies that may be impacted by tire wear particles.


Participants acknowledged that the roundtables were a first step to share knowledge on tire wear
particles in waterways. They affirmed an interest in continued collaboration among Federal
agencies, Tribes, states, utilities, industry, transportation departments, and other interested
stakeholders. Participants suggested convening stakeholders in a consistent and holistic way to
build and connect a community of practitioners interested in developing long-term solutions for
tire wear particle pollution.



Baensch-Baltruschat, B., et al., Tyre and road wear particles (TRWP)-A review of generation,
properties, emissions, human health risk, ecotoxicity, and fate in the environment. Science of
the Total Environment, 2020. 733: p. 137823.

Baensch-Baltruschat, B., et al., Tyre and road wear particles-A calculation of generation,
transport and release to water and soil with special regard to German roads. Science of the
Total Environment, 2021. 752: p. 141939.

Brahney, J., et al., Constraining the atmospheric limb of the plastic cycle. Proceedings of the
National Academy of Sciences, 2021. 118(16).

Chibwe, L., et al., A Deep Dive into the Complex Chemical Mixture and Toxicity of Tire Wear
Particle Leachate in Fathead Minnow. Environmental Toxicology and Chemistry, 2021.
00(00): p. 10.

Johannesson, M. & Lithner. D. Potential policy instruments and measures against microplastics
from tyre and road wear: Mapping and prioritisation, VTI rapport, ISSN 0347-6030; 1092A;
2022. p. 112.

Kole, P. J., et al., Wear and tear of tyres: a stealthy source of microplastics in the environment.
International journal of environmental research and public health, 2017. 14(10): p. 1265.

Luo, Z., et al., Environmental occurrence, fate, impact, and potential solution of tire

microplastics: Similarities and differences with tire wear particles. Sci Total Environ, 2021.
795: p. 148902.

Moran, K. D., et al. A Synthesis of Microplastic Sources and Pathways to Urban Runoff, 2021.
SFEI Technical Report SFEI Contribution # 1049; 2021. P. 138

Wagner, S., et al., Tire wear particles in the aquatic environment-a review on generation,
analysis, occurrence, fate and effects. Water research, 2018. 139: p. 83-100.

Wang, C., J. Zhao, and B. Xing, Environmental source, fate, and toxicity of microplastics.
Journal of hazardous materials, 2020: p. 124357.

Werbowski, L., et al., Urban Stormwater Runoff: A Major Pathway for Anthropogenic Particles,
Black Rubbery Fragments, and Other Types of Microplastics to Urban Receiving Waters.
ACS EST Water, 2021, 1, 6, 1420-1428.



Alliance for Automotive Innovation
Bay Area Clean Water Agencies

Bellingham, Washington, and Washington State 6PPD-quinone Subgroup
Brown & Caldwell

California Association of Sanitation Agencies

California Stormwater Quality Association

Central Contra Costa Sanitary District

City of Seattle

College of Charleston

Goodyear Tire & Rubber Company

Hoopa Valley Tribe

National Asphalt Paving Association

National Association of Clean Water Agencies

New England Interstate Water Pollution Control Commission

New Jersey Department of Environmental Protection

North Carolina Department of Transportation's Highway Stormwater Program

Ocean Conservancy

Oregon Department of Transportation

Oregon State University

Pew Charitable Trusts

Puget Sound Partnership

San Francisco Bay Regional Water Quality Control Board
San Francisco Estuary Institute
Talk Strategies

Texas Commission of Environmental Quality

U.S. Environmental Protection Agency (Office of Wetlands, Oceans and Watersheds, Office of
Wastewater Management, Office of Research and Development, regional offices and laboratories)

U.S. Tire Manufacturers Association

Virginia Department of Transportation

Washington State Department of Ecology

Zero Waste Washington



San Francisco Estuary Institute (SFEI) has a fact sheet on microplastics from tire wear particles
in the San Francisco Bay and a Synthesis of Mixoplastic Sources and Pathways to Urban Runoff
that includes an outline of potential tire wear particle mitigation options:

•	https://www.sfei.ore/documents/microplastics4ire-particles-san-francisco-baY-factslieet-0

•	https://www.sfei.org/docurnents/svnthesis-microplastic-sources-and-pathwavs-urban-


European Review of Mitigation Options from the Swedish National Road and Transport
Research Institute, 2022

•	https://www.vti.se/en/archives/news/archives/2022-03-02-how-microplastic-pollution-

EPA's Trash Free Waters program published and recently updated a Report on Priority
Microplastics Research Needs:

•	https://www.epa.gov/sYStem/files/documents/2Q2 1 -1 -report-on-priori tv-
microplastics-research-needs 0.pdf

The EPA laboratory in Corvallis, Oregon, and EPA Region 10 in Seattle are creating an
ecohydrological model to assess the effectiveness of green and gray infrastructure improvements
meant to reduce stormwater contaminant loads to Seattle's Longfellow Creek. The creek
experiences high rates of coho salmon pre-spawn mortality associated with lethal concentrations
of 6PPD-quinone associated with tire wear particles.

•	https://ctpub.epa.gov/si/si public record Report.cfm?dirEntrvId=352990&Lab=CPHEA.

The Tire Industry Project (TIP) is a forum supported by U.S. Tire Manufacturers Association
(USTMA) and the World Business Council for Sustainable Development (WBCSD):

•	https://www.wbcsd.ore/Sector-Proiects/Tire-Industrv-Proiect

TIP has a web page on tire and road wear particles and other material research:

•	https://www.wbcsd.ore/Sector-Proiects/Tire-Industry-Proiect/Resources/Tire-and-Road-

Cryo-milled tire tread samples are also available for researchers from TIP:

•	https://www.ustires.ore/cmtt

Studies were shared regarding tire wear particles and environmental effects:

•	https://azdot.gov/sites/default/files/2019/05/tire-wear-emissions-for-asphalt~rubber-

•	https://www.researchgate.net/publication/35798ii »>> Toxicity of Micro and Nano Tir
e Particles and I.eachate for Model I ushwater Oreanisms

•	https://envi ronm ent.transportati on. org/teri -idea/ storm water-managem ent-to-address-
hi gh way-runoff-toxi citv-associ ated-wi th-ti re-wear/


Washington State Department of Ecology assessed potential hazards of 6PPD-quinone and

•	https://www.ezview.wa.gov/Portals/ 1962/Documents/6ppd/6PPD%20Alternatives%20T
echnical%20Memo.pdf#:~:text=In%20202 l%2C%20the%20Washington%20State%20L

Oregon Department of Transportation has a Stormwater Technology Testing Center:

•	https:// sttcoregon. com/

The Watershed Game, created by the University of Minnesota-Duluth, helps participants learn
how land use affects water quality and natural resources:

•	https://seagrant.umn. edu/watershed-game?msclkid=5bc28553af8fllecb02a5	:cb2f8