This matters because tyres shed a lot of material into the environment.
What else is coming out of our tailpipes?
Tightening tailpipe regulations is a natural impulse in a post-Dieselgate world. However, we are in danger of over-regulating familiar, easy-to-measure emissions such as CO2 and NOx while ignoring a wide range of other, potentially harmful substances that can now be measured but have previously been ignored.