‘Scientists Driven to Understand Microplastics from Tyres and Their Effects on the Natural World’

Recently the media has been buzzing with shocking stories about the negative impact of plastic on our oceans and one type of plastic waste in particular; ‘microplastics’ has really caught the public’s attention. Microplastics are identified as solid, polymer (a plastic chemical)-based materials that don’t dissolve in water and are less than five millimetres in size – that’s roughly the size of an apple pip or smaller.

We’ve all heard of the microbeads once used in beauty products and how plastic bottles break down into tiny fragments, contributing to the plastic pollution issue. But one source of microplastics has become increasingly concerning since its significance was revealed in recent years, fuelling scientists’ interest in the problem. Microplastics from tyres; fragments of tyre worn away by energy (friction) of the rolling tyre tread against the road surface when driving. A typical all-season tyre can contain 40 different types of chemicals, along with polyester and nylon (plastic) fabrics which can cause harm to ecosystems when shed.

Image 1: A tyre wear particle seen under the microscope (image credit: Knight et al. 2020)

A recent study by Lydia Knight and her colleagues from the universities of Plymouth and Surrey set out to measure how many of these sausage-shaped particles are being blown, washed and carried into the natural environment. They also wanted to know what road conditions might speed-up tyre wear. To do this they collected samples of mud from the bottom of multiple drains along a major road in the city of Plymouth, Devon. The drains were chosen based on their location along the road in order to test areas with different levels of traffic and therefore different rates of braking and acceleration. They also tested roadside soil and mud from the local estuary.

90.9% of all the samples had tyre particles present – a staggering statistic! The roadside soil had the highest amounts, with quantities decreasing the further away you get from the road. This study shows several potential pathways of tyre fragments in the natural environment including particles dispersing via the atmosphere or coming directly from the road. They can also emerge from storm water run-off from the drains – which often flow into local waterways, releasing toxic chemicals and potentially damaging organisms.

Image 2: A well-worn car tyre. 1.1kg of microplastics have been shed into the environment when a single car tyre reaches the end of its lifespan

This valuable research shows fragments of tyre are an important source of microplastics in the natural world, but more research is needed to look at how toxic the particles are to the environment and ocean. This report also highlighted that the highest concentrations of particles were recorded in areas where braking was more frequent and aggressive but amounts also increased with vehicle load and under (or over) inflation of tyres. Deviations in wheel alignment and driving at high speeds also led to faster tyre shedding, hinting that in order to limit the number of tyre wear particles we each personally emit, we need to slow down and maintain our vehicles!

Main paper citation:

Knight L., Parker-Jurd F., Al-Sid-Cheikh M., Thompson RC (2020). Tyre wear particles: an abundant yet widely unreported microplastic? Environmental Science and Pollution Research Springer: Available at: doi 10.1007/s11356-020-08187-4

Further reading:

Website link to National Geographic article on tyre microplastics study: https://www.nationalgeographic.com/environment/article/tires-unseen-plastic-polluter

Scientific study (journal article) based on effects of car tyre microplastics in the environment:https://microplastics.springeropen.com/articles/10.1186/s43591-021-00008-w

Website link to information on how you can help the issue: https://friendsoftheearth.uk/sustainable-living/tyres-and-microplastics-time-reinvent-wheel