I’m not sure if a study exists for it, but I’d assume walking produces more microplastics/km than bicycling because of how soft shoe rubber is and how scrubby the action is. Who knows. There is a study I saw that said that walking produces more CO2 per km than cycling, but I’m not sure if this is parallel to microplastic emissions.

The logic will make sense if you think that tailpipe emissions are so litte, it’s almost not worth considering in comparison to tire emissions. So the next step is to say “so how do we limit the microplastics in the air and in the ground on a necessary part of transportation”- the answer is to make it smaller and lighter. And if you want to go distances that you can’t get to by bike, that’s where public transportation comes in.