Microparticles from road tyres are “high concern” pollutants, research shows

The new study is part of the University's ongoing TYRE-LOSS project
Tyre wear particles captured from the road network in wetlands used to trap stormwater. Taken at the University of Plymouth Scanning Electron Microscopy Unit

Plastic microparticles released into the environment from common road tyres should be treated as a “high concern” pollutant, that may exceed chronic safety limits in some heavily contaminated environments, new research has shown.
A team of researchers, including experts from the University of Plymouth and the University of Exeter, looked at the chronic toxicity of particles and chemical leachates found on a series of popular tyre brands.
They then looked at the effect these particles and chemicals would have on small planktonic crustaceans, the water flea (Daphnia magna).
They discovered that the plastic pollutants from the tyres showed a distinct effect on both the reproduction and development of the water flea – which also displayed visible particle uptake within their digestive tract.
When looking at the leachates – liquid that has passed through the tyre material, taking some of the harmful chemicals with it – they found a strong presence of zinc, titanium and strontium as well as many organic chemicals.
Overall, of the numerous organic chemicals present during the test, more than 50 were found across all five tyre brands, with a significant number of those chemicals classified as very toxic.
This new research shows that tyre particles are hazardous pollutants, and should be treated as a particular concern close, to or possibly above, chronic environmental safety limits in some locations, researchers say.
The research, published in the Journal of Hazardous Materials, is part of the TYRE-LOSS: Lost at Sea – where are all the tyre particles? project being led by the University of Plymouth with funding from the Natural Environment Research Council.
Professor Richard Thompson OBE FRS , Head of the International Marine Litter Research Unit at the University of Plymouth, leads the TYRE-LOSS project and is a co-author on the new study.

Our previous work has shown that road debris is a major source of microplastics in the environment. In recent years, we have been working with partners across research and industry to determine how those particles distribute and their potential to cause harm. This new study is of key importance because it demonstrates the potential for harmful effects on an aquatic invertebrate species, at concentrations similar to those we have recorded near to roads in the UK. It is clearly an area we need to explore further.

Richard Thompson OBE FRSProfessor Richard Thompson OBE FRS
Head of the International Marine Litter Research Unit

Tyres exert a complex toxic pressure to wildlife because they release plenty of toxic chemicals as well as tiny particles that can be ingested, so both chemical and physical effects are occurring.

Dr Paul Boisseaux
Postdoctoral Research Fellow in Ecotoxicology at the University of Exeter, and lead author of the study
The use of tyres by cars, buses and other vehicles is a ubiquitous feature of modern life, all served by a mass global tyre industry that is forecast to grow around three per cent each year.
Tyre-tread particles generated during roadway use are a major environmental pollutant, with a significant proportion being washed away into waterways near traffic networks. It is estimated at around 18 per cent of these particles eventually reach freshwater, while two per cent reach estuaries.
However, while previous research suggested there may be concentrations of these particles in the environment, the toxicological effects they have on aquatic organisms were less well understood.
For this study, the team used several popular tyre brands from around the world to generate a tyre tread microparticle mixture. The toxicity of both particles and chemical leachates were then studied on the test species, the water flea.
They found that, over a three-week period, pristine tyre tread microparticles were more toxic (concentration being lethal for 50% of the population, LC50, is 60 mg.L‑1) than chemical leachates alone (LC50 542 mg.L‑1).
The results suggest the particles were more toxic to water flea than the more commonly studied polyethylene microplastics.
  • The full study – Boisseaux et al: Deep dive into the chronic toxicity of tyre particle mixtures and their leachates – is published in Journal of Hazardous Materials, DOI: 10.1016/j.jhazmat.2024.133580.

Read about more research linked to this study

A study led by the University of Plymouth is one of the first worldwide to identify tyre particles as a major and additional source of microplastics (Credit Getty Images)

Major study reveals substantial quantities of tyre particles contaminating our rivers and ocean

Getty image 872418096 tyres 

Project aims to reveal the fate of tyre particles in the marine environment

Tyre wear concept. Old car bald tyre with very little tread remaining.

Scientists continue work to establish the fate and impact of tyre wear particles in the environment

The underestimated microplastic

330 billion road miles are driven in the UK every year, generating particles of synthetic rubber as a consequence of friction between the tyre and the road surface. It has been estimated that tyre wear could account for 65% (18,000 tonnes annually) of all microplastics released to UK surface waters, however their fate and impact remains largely unknown. Tyre particles are not currently well documented in environmental data potentially due to the difficulty in identifying them from other plastics in environmental samples.

The number of road vehicles is set to double by 2050 leading to increased particle emissions; however, there are interventions that could reduce the rate of tyre particle generation.