When you think about car pollution, you probably think mainly about exhaust emissions.
We’ve been pointing out the global-warming and health-harming effects of petrol and diesel vehicles for years.
But recent research shows there’s another serious, maybe more surprising environmental threat from road traffic. It comes from tyres.
Although we loosely call them ‘rubber’, vehicle tyres are actually made from a complex blend of a lot of mostly synthetic materials and chemicals, including different types of plastic.
As cars and trucks pound along our roads, they gradually shed tiny bits of tyre material. Think about how tyre tread slowly but inevitably wears down until tyres need replacing.
When it rains, those tyre particles – essentially microplastics – are washed off the road surface into drains or waterways. They will often end up in our rivers and seas.
A new report by Eunomia Research & Consulting indicates that vehicle tyres are the single biggest cause of microplastic pollution in ‘surface waters’ – meaning rivers, lakes, wetlands and oceans in the UK.
The Eunomia report, Reducing Household Contributions to Marine Plastic Pollution [PDF], highlights the main everyday activities that lead to plastic getting into our seas. And looks at ways of stopping it.
It turns out vehicle tyres are the main source – who knew? It’s estimated that an astonishing half a million tonnes of tyre-wear fragments are released every year across Europe. The UK’s share of that is around 68,000 tonnes with up to 19,000 tonnes of microplastic tyre pollution getting into our waterways, rivers and seas each year.
We want to see the government use these findings to create an action plan to cut plastic pollution from tyres.
Microplastics in general can get into the food chain and harm marine life – they've even been found in human poo.
When the rubber hits the road
As we’ve said, rubber tyres aren’t strictly rubber nowadays – at least not in the sense of natural latex rubber, harvested from trees.
Natural rubber may be a minor component (sometimes as little as 20%), but the bulk of a modern tyre is a mix of synthetic compounds, fillers, binders, plasticisers and other chemical additives to add strength, weatherproofness etc. The exact composition will vary and is often kept secret by tyre manufacturers.
One important but less-than-obvious ingredient added to tyres is carbon black. It’s a dark sooty material usually sourced from burning fossil fuels, and is used to increase tyre strength and resistance to UV light. It’s the main reason tyres are black.
Before carbon black was introduced, over 100 years ago, tyres were usually creamy white – the colour of natural latex. Carbon black is known not to be biodegradable, and is a ‘possible human carcinogen’, according to a report published by the International Agency for Research on Cancer.
Rubber tyres = plastic waste
If you hadn’t considered tyres as a big problem before, it’s time to think again.
According to government figures, there are around 30 million cars licensed for use in the UK. That means 120 million car tyres on our roads. And that’s not including all the lorries and massive multi-wheeled HGVs, from the UK and elsewhere, that thunder down our streets and motorways every day. All that rubber on the road is potential plastic pollution down the drain.
Modern tyres include a variety of synthetic polymers, with names like styrene butadiene and halobutyl rubber, and polyester cord fibres to strengthen the internal structure. In short, tyres are essentially yet more big chunks of plastic. And when they break down they behave and persist like other plastics in the environment.
Once in the ocean, tyre particles adsorb and concentrate toxic pollutants from seawater, like other microplastics do. This makes them even more poisonous to animals that mistake them for food or absorb them through their gills or skin.
Airborne microparticles (and even smaller nanoparticles) are a worry on land too. It is estimated that up to 10% of tyre wear is generated as airborne particles, which contribute to ongoing problems of air pollution and lung problems in UK cities.
The truth is it can be very difficult to identify and track exactly where all the tiny tyre particles go, and how they affect people and wildlife locally and more widely. But the sheer volume of particles that we know tyres create is a big cause for concern, and a subject of ongoing research.
Keeping tyre pollution out of our oceans
The Eunomia report findings highlight the need for a government action plan to redress the huge problem of vehicle tyre pollution.
The main elements that need to be considered are:
- How tyres are made.
- How tyres wear and shed material on the road.
- How people drive.
- How tyre particles are removed from roads.
- What alternatives there are to existing tyres.
We’ve got several recommendations for tackling tyre pollution from all these angles. They will require cooperation from national and local government, industry and all of us in our everyday lives.
How government and local authorities can cut tyre pollution
1. Test and label tyres
We want to see a new government-backed test to make it clear how resistant each type of tyre is to wear and tear – with clear labels for buyers.
Tyres with the highest rates of tread abrasion could be banned from sale completely. At the moment there are European tyre labelling regulations covering things like wet grip, noise, and fuel consumption, but not wear and tear.
2. Introduce a tyre levy
We’re calling on the government to consider a small charge on each tyre sold. This could vary depending on how the tyre is made and how resistant it is to wear and tear. The money raised could be used to help pay for further research and to implement the best solutions to the problem of microplastic pollution.
3. Capture tyre pollution from roads
For example more efficient use of roadside gully pots – which are used to catch debris, sediment and microplastics before they get into the drains or waterways. These can be up to 80% effective if they are emptied regularly, but unfortunately they’re often allowed to overfill/overflow.
Another option is to use porous asphalt as a road material. This can trap tyre particles in the road surface for later removal. It’s also known to be a safer road surface for drivers, as it reduces standing water and spray, although it’s more expensive than traditional asphalt.
4. Increase road cleaning
Road sweeping can be used to mop up tyre particles from the roads or adjacent paths. Scheduling is important for this, as it’s best done just before it rains. The UK also has detailed traffic data which a local authority can use to target the busiest roads in the most effective way.
5. Encourage less driving
Introduce measures and incentives to reduce the number of vehicles on the roads. For instance better public transport, cycling facilities and walking routes. As well as cutting microplastic pollution, this could have knock-on benefits all round, including public health and road safety.
How industry can help cut tyre pollution
1. Make tyres more resilient to wear and tear
At the moment there’s no meaningful incentive for tyre manufactures to prolong the life of their tyres, ie reduce the wear rate of the tread.
The position of the European Tyre Manufactures Association (ETRMA) is that driver behaviour has the biggest effect on tyre wear. Even if that’s true (we’ll look at this in a minute), it doesn’t change the fact that better wear characteristics in the tyre design will undoubtedly reduce microplastic pollution overall.
It’s sometimes suggested that improving the wear rate can reduce tyre grip and therefore safety, but there’s no clear correlation between these two for tyres on the EU market. Evidence suggests that manufacturers can and do make tyres that grip well and have better wear qualities.
We’d like to see manufacturers take that further, and prioritise the development of tyres that maintain (even improve) performance in terms of efficiency, safety and noise, at the same time as reducing the rate at which the tyre tread wears.
2. Alternative tyre materials
The tyre manufacturing industry has apparently been working on biodegradable polymers for many years, although there’s nothing commercially available so far.
One of the big challenges is to find a material that biodegrades safely and effectively in the environment, but is tough enough not to disintegrate too easily or quickly in everyday use.
Michelin has proposed an airless tyre that can be 3D printed from organic material and is fully biodegradable.
But the car industry is well known for challenging convention with outlandish concept designs, and we’re aware that’s not the same as producing something commercially viable, at least in the near future.
3. Tyre retailers should help guide buyers
Both in person and online, tyre sellers have a big influence on what people buy.
In the UK alone around 50 million tyres are sold every year. But because tyres aren’t a frequent purchase for most people, buyers generally don’t know enough about them, so rely on the apparent expertise of the retailer.
Retailers should actively support the tyre wear rate labelling scheme, and help explain the options at the point of purchase.
Research shows that consumers already find the concept of mileage (how many miles the tyre will last) to be equally as important as the tyre’s effect on fuel efficiency.
How we can all help
1. Choose to walk, cycle or take public transport
This is the most preferable option, wherever possible. Shared vehicle journeys rather than single-occupancy cars would be the next best thing. There are plenty of car-sharing schemes you can find out about online.
Bear in mind too that even electric cars, which are otherwise better for the environment, still have the same kind of synthetic rubber tyres as conventional cars, so still cause microplastic pollution.
2. If you have to drive, go gently
When a journey by private car is unavoidable, there are several small things that drivers can do to reduce tyre wear and therefore microplastic shedding. These generally coincide with what’s widely considered eco-driving. For example:
- Drive smoothly and avoiding aggressive manoeuvring and abrupt cornering.
- Accelerate gently, and don't over-brake unless you have to. Break pad wear and tear is yet another source of microplastic pollution on the roads.
- Drive with the correct tyre pressure.
- Remove unnecessary weight from the vehicle.
- Choose to drive smaller, lower-weight vehicles.
So there’s a role we can all play – but the main push has to come from government. We hope the new Eunomia report will drive urgent government action to help keep tyre pollution out of our rivers and seas.