Driving is not just an air pollution and climate change problem: turns out, it just might be the largest contributor of microplastics in coastal waters.

That is one of many new findings from the most comprehensive study to date on microplastics in the US state of California.

Rainfall washes more than 7 trillion microplastics, much of it tyre particles left behind on streets, into San Francisco Bay each year – an amount 300 times greater than what comes from microfibres washing off polyester clothes, microbeads from beauty products and the many other plastics washing down our sinks and sewers.