Tires as a source of microparticles

Some time ago I had a lively discussion about micro particles emitted by vehicles. The focus was on cars and bikes.

The devil's advocate, my discussion partner, claimed that the emission of micro particles by a bike is probably as high that of a car (as I remember, he meant the micro particles in the exhaust gas).

This discussion was on my mind since taking place. Today I read some articles and studies about that topic. Those focus on the emission of particles by tires but it's good start to get an overview.

This Spiegel-Online article (german language) let me to this study by Fraunhofer institute UMSICHT (german language). There the sources of micro particles (plastics) is listed in quite some detail. Unfortunately only the mass per year and person are listed not the mass per kilometer. To get a better overview I looked for statistics about the traveled distance of bikes and cars per year. Here you can find information about cars and here about bikes.

Another interesting article can be found in the current Suedeutsche Zeitung from 8th September 2018 or on their website behind a paywall (german language). Bikes