We’re frequently told that cars are bad for the planet. That’s why we’re being pushed towards driving electric cars. But exhaust emissions aren’t the only nasties to come from our cars. Every time we drive, tiny bits of rubber fly off our tyres and into the atmosphere. In some cases, these particles are so small they’re considered to be microplastics. Read on to see if they really pose a threat.
How do tyres release fragments?
When a tyre runs along a road it generates friction. By rubbing against the road surface, both the tyre and road surface wear – that’s why periodically you have to replace your tyres. As part of the wearing process, tiny fragments of tyre are released. These are so small they’re called particles, or in some cases microparticles.
How big are the particles?
The next time you look in the gutter, you’ll see grit. Much of this is man made and consists of pieces of worn road, tyre fragments, brake dust plus exhaust and other environmental emissions. The tyre and road particle element of this grit varies in size from between 0.01mm to 0.0025mm. That’s stretching from tiny to microscopic. The larger pieces are the sort of stuff that ends up on the end of a street sweeper’s broom. The smaller particles can become airborne and in some cases are small enough for us to inhale.
What are tyre particles made of?
Sir David Attenborough among others has worked hard to bring the effect of microplastics to our attention. But did you know that tyre particles are considered to be microplastics? This is because tyres are no longer made purely from rubber. They contain between 20 and 40 ingredients and some of these are polymers, which are considered to be plastic.
How serious is the problem?
This is where the experts can’t seem to agree. The Organisation for Economic Cooperation and Development (OECD) claims that a road used by 25,000 vehicles a day will see up to 9kg of tyre dust per kilometre emitted. However, scientific tests conducted by the tyre industry suggest it’s a fraction of this. Tyre makers estimates 1kg of tyre particle emissions per person per year in Europe.
How bad for us are these particles?
Again, the experts disagree. The OECD seems to think they’re very bad. Shayne MacLachlan of the OECD Environment Directorate wrote: “A lot of non-exhaust pollution from tyres and brakes winds up in rivers, streams and lakes. They produce particulate matter which is more harmful for humans than gas pollutants like ozone and nitrogen dioxide.”
However, the tyre industry counters with research that it claims shows tyre dust isn’t nearly as harmful as some might think. In tests on rats it found a no-observable-adverse-effect level. More tests concluded that tyre wear particles are low risk to aquatic eco systems. And research into tyre particles in the Seine river in France found that because particles are heavier than water, they sink and therefore don’t make it into the sea. And it claims that nearly two thirds of tyre particles (61 per cent) end up coming to rest beside roads.
What does this mean for drivers?
In the short term there’s little we can do, other than be more relaxed drivers. Tyre particle expert Susanne Buchholz from tyre maker Continental says: “The biggest part in the number of particles released is played by driver behaviour.” In other words, the slower you drive, the fewer particles your tyres will release and the more miles you’ll get out of your rubber.
In the long term, we might be looking at tyre wear featuring on the labels you see when you buy tyres. That would enable consumers to choose a tyre based on how many particles it might release.
This is a problem that won’t go away
Currently, experts might disagree on how bad for us and the environment tyre particles really are. However, as take-up of electric cars increases and exhaust emissions falls, the focus will fall on other emissions from cars. Sadly, tyre particles are an unavoidable by-product of driving a car.