So if you take someone in the United States, driving an average of 25,000 km per year, they are generating something like 2,750 g of microplastics. If that same person mountain bikes 25 km per week for a year (1,300 km) they are generating something like 46 g of microplastics. I’m all for making mountain biking more environmentally friendly, but it looks like a rounding error on our microplastic emissions when looking at other sources. Combined with giving people more reason to protect nature, I’d guess it’s a net positive. Here in the US, wet need to fix our land use and transportation, as car dependency is not compatible with a livable planet.

Butyl rubber. Iirc, it's combined with plastics for bike tires. I'm hoping we can find biodegradable alternatives for cars and bikes. That said, the impact of bikes and ebikes is most likely far smaller than the millions of cars (including EVs) on the road across continents.

Ideally, we need to make rail a huge priority across the north and south American contingents. Rail and bikes will take a chunk out of microplastic production.