Q&A about Tire and Road Wear Particle Research

Marisa Kreider, PhD, DABT, Principal Science Advisor

Kenneth Unice, MS, Principal Health Scientist

Cardno ChemRisk’s multi-disciplinary team of scientists has been a product stewardship and sustainability consultant to the tire industry for more than 15 years. An important focus of our research has been on Tire and Road Wear Particles (TRWP) generated by the necessary friction at the surface of the tire and road. Our team is proud to have assisted the industry address human and environmental health risk questions about their products through our applied research efforts. Our early work included leading a “State of Knowledge” assessment completed in 2007, which provided a product sustainability research “roadmap” for the industry. We began our research in 2008 and published our first TRWP study in 2010, coincident with emerging interest in non-exhaust emissions from vehicles and well before the global emphasis on plastic (non-rubber) polymeric debris in the environment. Although tire particles are not scientifically defined as “plastic”, some agencies and scientists have expanded the definition of “microplastic” to include TRWP. The purpose of this Q&A is to address questions from regulatory agencies, members of the public, scientists and journalists interested in our work.

What was the goal of Cardno ChemRisk’s TRWP research?

The goal of our research sponsored by the tire industry has been to fill knowledge gaps in the assessment of the potential human or ecological risks associated with particles generated by the necessary friction between a tire and the road surface. Our work has been guided by the risk assessment approach as described by the National Academy of Sciences (1983) and applied by most U.S. health agencies. This approach provides a systematic structure for the synthesis of hazard and exposure information to characterize the likelihood of adverse effects.

What are some examples of TRWP peer-reviewed research performed at Cardno?

Our work since 2007 has addressed questions of TRWP characterization, hazard, exposure and risk, which closely align with the topics under discussion today in 2020 for all types of microplastics. We value transparency, and have published a number of tire industry sponsored studies in the peer-reviewed literature. Publishing in peer-reviewed literature is a critical aspect of the research effort since this process includes independent vetting of the research for quality and merit by scientists whose identity is not disclosed to the publication authors. Our team has published:

  • a physical and chemical characterization of TRWP in 2010, which included electron microscopy visualization and was supported by on-road and laboratory collection of particles;
  • acute and chronic aquatic toxicity studies in 2011 and 2012;
  • a subacute inhalation toxicity study in 2012;
  • a novel method for detection of quantification of TRWP mass in environmental samples (soil, sediment and air) in 2012 followed by publication of the concentration of TRWP in the environment in 2013 (sediment), 2014 (air PM-10 fraction) and 2019 (air PM-2.5 fraction);
  • a laboratory study of the effects of TRWP weathering in the environment on the fate of organic chemical additives used in tread manufacture in 2015;
  • a two part computational methodology study of the fate and transport of TRWP in watersheds completed in 2018; and
  • a human health risk assessment for exposure to TRWP in air published in 2019.

Does Cardno ChemRisk team with other researchers or perform all of the work “in house”?

The majority of studies completed by Cardno ChemRisk have involved international and independent partner laboratories drawing on a global pool of specialty expertise. Some examples of laboratories we have collaborated with include:

  • Akron Rubber Development Laboratory (United States)
  • Brixham Laboratory (United Kingdom)
  • Chemical Evaluation and Research Institute (Japan)
  • Deltares (Netherlands)
  • German Federal Highway Research Institute (BASt)
  • Lovelace Respiratory Research Institute (United States)
  • LRCCP (Laboratoire de Recherches et de Contrôle du Caoutchouc et des Plastiques - French Rubber and Plastics Research and Testing Laboratory)
  • Nautilus Environmental, LLC (United States)
  • Pacific EcoRisk (United States)
  • Solar Light (United States)

Are TRWP a type of microplastic?

A global consensus definition of microplastics is lacking. TRWP are small particles (<5 mm) that contain a fraction of polymeric material, and thus are consistent with some definitions of microplastics.
Irrespective of definitions, the principle of shared responsibility and stewardship for human health and the environment suggests that all forms of synthetic particles (plastics, combustion debris, etc.) should be carefully studied within the context of how these particles interact with naturally occurring particles and organisms in the environment.

Has Cardno ChemRisk’s research meaningfully contributed to the broader field of microplastics?

Microplastics research is a dynamic and evolving field drawing on a number of disciplines. Our work has contributed new ideas to this vibrant research community in a number of ways. Our early work provided clear methods for laboratory generation of TRWP closely resembling the particle generated in the real environment, whereas previously most research had been performed using poor surrogates. We then evaluated aquatic and inhalation toxicity of these particles to address questions about environmental health risk. We also demonstrated the use of an internal standard quantitative mass analysis by pyrolysis-GC/MS to determine the amount of TRWP in environmental media, and published the global estimates of TRWP concentrations in the sediments of three watersheds in Japan, the United States and France in 2013. This work was done several years before microplastics became a focus of regulatory agencies, researchers and the public. In 2015, we worked with a partner laboratory to build an environmental chamber to artificially weather TRWP, and subsequently show how weathering affects the availability of organic additive chemicals used in the manufacture of tread. More recently, between 2017 and 2018, we collaborated with the research institute Deltares to publish one of the first computational modeling methodologies for evaluating the fate and transport of a microplastic in the environment, using TRWP as an example.

Who sponsored Cardno ChemRisk’s tire industry research?

Individual companies and trade associations sponsor research at research universities, non-profit institutions, governmental laboratories and private consultancies. Much of our work has been sponsored by the Tire Industry Project organized under the World Business Council for Sustainable Development (WBCSD). Additionally, the European Tyre and Rubber Manufacturers’ Association (ETRMA) recently sponsored the computational study of the fate and transport of TRWP in watersheds. This funding is disclosed on all our research publications.

What processes are in place to ensure the independence and quality of the research?

Cardno ChemRisk is an independent consultancy that receives financial support from an industry sponsor, not unlike academic research universities that receive industry sponsorships. Our team requires a principle of scientific independence as a condition of accepting the work from sponsors. Thus, the design, conduct and conclusions of our research are completely independent of the sponsor. While the tire industry has identified areas of research based on data gaps and is regularly updated with respect to progress on the research, any conclusions on our work addressing those data gaps is not influenced by the member companies of the industry, nor by the trade associations that coordinate the completion of the work.

The quality of work is ensured through the presentation of our research in scientific peer reviewed publications and at scientific conferences. Additionally, most of our work has been completed with independent teaming partner laboratories or consultancies recognized globally for their expertise. For example, to complete our recent microplastics computational study we interviewed six research groups or non-profit institutes and selected Deltares as our partner based on technical rigor of their capabilities. Finally, throughout the history of our work with the tire industry, the sponsor has appointed external science advisors and/or quality assurance committee members to advise the industry on the scientific rigor and quality of the work. These technical advisors and assurance committee members are well- respected members of their disciplines.

What are the qualifications of Cardno ChemRisk to perform these studies?

Cardno ChemRisk’s multi-disciplinary team of engineers, toxicologists, industrial hygienists and environmental scientists has a robust history in human health and environmental risk assessment that can be applied to products and their lifecycle. Our team has included leaders in their respective fields with decades of integrated environmental health research experience throughout the history of our work for the tire industry. The scientists who contributed to the work are active in professional societies, serve frequently as peer reviewers for journal editors, and excel in cross-discipline scientific research.

Kreider, M.L., Panko, J.M., McAtee, B.L., Sweet, L.I. and Finley, B.L., 2010. Physical and chemical characterization of tire-related particles: Comparison of particles generated using different methodologies. Science of the Total Environment, 408(3), pp.652-659.

Kreider, M.L., Doyle-Eisele, M., Russell, R.G., McDonald, J.D. and Panko, J.M., 2012. Evaluation of potential for toxicity from subacute inhalation of tire and road wear particles in rats. Inhalation toxicology, 24(13), pp.907-917.

Kreider, M.L., Unice, K.M. and Panko, J.M., 2019. Human health risk assessment of Tire and Road Wear Particles (TRWP) in air. Human and Ecological Risk Assessment: An International Journal, pp.1-19.

Marwood, C., McAtee, B., Kreider, M., Ogle, R.S., Finley, B., Sweet, L. and Panko, J., 2011. Acute aquatic toxicity of tire and road wear particles to alga, daphnid, and fish. Ecotoxicology, 20(8), p.2079.
National Research Council, 1983. Risk assessment in the federal government: managing the process. National Academies Press.

Panko, J.M., Kreider, M.L., McAtee, B.L. and Marwood, C., 2013. Chronic toxicity of tire and road wear particles to water-and sediment-dwelling organisms. Ecotoxicology, 22(1), pp.13-21.

Panko, J.M., Chu, J., Kreider, M.L. and Unice, K.M., 2013. Measurement of airborne concentrations of tire and road wear particles in urban and rural areas of France, Japan, and the United States.
Atmospheric Environment, 72, pp.192-199.

Panko, J.M., Hitchcock, K.M., Fuller, G.W. and Green, D., 2019. Evaluation of tire wear contribution to pm2.5 in urban environments. Atmosphere, 10(2), p.99.

Unice, K.M., Kreider, M.L. and Panko, J.M., 2012. Use of a deuterated internal standard with pyrolysis- GC/MS dimeric marker analysis to quantify tire tread particles in the environment. International journal of environmental research and public health, 9(11), pp.4033-4055.

Unice, K.M., Kreider, M.L. and Panko, J.M., 2013. Comparison of tire and road wear particle concentrations in sediment for watersheds in France, Japan, and the United States by quantitative pyrolysis GC/MS analysis. Environmental science & technology, 47(15), pp.8138-8147.

Unice, K.M., Bare, J.L., Kreider, M.L. and Panko, J.M., 2015. Experimental methodology for assessing the environmental fate of organic chemicals in polymer matrices using column leaching studies and OECD 308 water/sediment systems: application to tire and road wear particles. Science of The Total Environment, 533, pp.476-487.

Unice, K.M., Weeber, M.P., Abramson, M.M., Reid, R.C.D., van Gils, J.A.G., Markus, A.A., Vethaak, A.D. and Panko, J.M., 2019. Characterizing export of land-based microplastics to the estuary-Part I: Application of integrated geospatial microplastic transport models to assess tire and road wear particles in the Seine watershed. Science of the Total Environment, 646, pp.1639-1649.

Unice, K.M., Weeber, M.P., Abramson, M.M., Reid, R.C.D., van Gils, J.A.G., Markus, A.A., Vethaak, A.D. and Panko, J.M., 2019. Characterizing export of land-based microplastics to the estuary-Part II: Sensitivity analysis of an integrated geospatial microplastic transport modeling assessment of tire and road wear particles. Science of the Total Environment, 646, pp.1650-1659.