Driving Cars Is by Far the Largest Cause of Microplastic Pollution in Oceans

My colleague Katherine Martinko has written that Synthetic Fabrics and Car Tires Are Major Source of Microplastic Pollution, but perhaps we should be reworking the title, because a new study concludes that plastic from tires generates vastly more microplastic waste than any other source. It's also carried by the wind, hence the title Atmospheric transport is a major pathway of microplastics to remote regions.

The average emissions are about .81 kg (1.78 pounds) per capita, for a total of 6.1 million tonnes; brake wear adds another half of a million tonnes. And this isn't just from burning rubber like my photo, it's from regular use, the wear and tear of driving. It was thought that most of this entered the oceans via rivers, but it turns out that they are airborne, and are found deposited on ice in polar regions.

Damian Carrington of The Guardian interviews one of the researchers about how this exceeds other sources:

“Roads are a very significant source of microplastics to remote areas, including the oceans,” said Andreas Stohl, from the Norwegian Institute for Air Research, who led the research. He said an average tyre loses 4kg during its lifetime. “It’s such a huge amount of plastic compared to, say, clothes,” whose fibres are commonly found in rivers, Stohl said. “You will not lose kilograms of plastic from your clothing.”

Stohl also says something that got me in so much trouble in a few years ago, in a post about electric cars:

Stohl said the issue of tyre and brake pollution is likely to get worse before it gets better as electric cars become more common: 'Electric cars are normally heavier than internal combustion engine cars. That means more wear on tyres and brakes.'

It should be noted that not all electric cars are heavier than internal-combustion-engine powered cars, and that electric cars have regenerative braking which reduces the amount of brake wear by about half. However, as electric pickups with giant battery packs come on the market, no doubt we will see the microplastic pollution increasing.

So why is it we spend so much time and energy worrying about plastics from our clothing and even our cosmetics, which are barely a rounding error, and don't get me started on drinking straws, while we continue ignoring cars? Likely because once again, nobody really likes to talk about the negative impact of cars and trucks, they are just too convenient, the industries behind them are much more powerful, and our society is designed around them. Talking about straws is much easier.

Why We Need to Drive Smaller, Lighter Cars (with Much Smaller Tires)

Of course, there are things we could do if we wanted to, or the regulators could do if they cared; according to the study,

 TWPs [tire wear particles] are produced by shear forces between the tread and the road pavement, generating coarse particles, or by volatilization generating submicronic particles. The wearing process depends on the type of tyre, road surface and vehicle characteristics, as well as on the vehicle’s state of operation.

That's why our title is different from The Guardian's, which said Car tyres are major source of ocean microplastics. It's the old "driver not car" thing that we talk about in crashes; a tire just sitting there doesn't wear down. Much comes down to the choice of vehicle and the way it's driven. That's why I previously wrote Why We Need Fewer, Smaller, Lighter, Slower Cars: Plastic Particulates From Tire Wear Are Being Found in the Arctic. And of course, lower speed limits.

But then, tires are mostly synthetic rubber made from fossil fuels; the bigger the car or truck, the bigger the tire, and more tire particles mean more money for the petrochemical industry, so don't expect any action here.