It seems natural rubber is not help. It can as well involve in microplastics. It still ends up acting like polymers and additives can still be harmful. Just because something is natural does not mean it is safe or is not made to be harmful when processed.

Less cars. Obviously they will continue to exist, but reducing car miles by: prioritizing mass transit, walking, and biking. Encouraging large companies and businesses to locate with density near stations and urban centers rather in suburbia. Increasing housing stock and density close to stations and urban centers to improve transit effectiveness and reduce commuting miles.

What alternate composition? I mean what is the no plastic alternative option?

Is there even a way to get same characteristic with say fully natural rubber. And would such rubber also be free of any risks?

Yes, also lighter cars.