Synthetic and natural rubber are polymers that break down into smaller polymer particles (usually—whether synthetic or natural—this would strictly be micro-rubbers rather than micro-plastics, but other than the former being elastic, they have pretty similar properties and issues, and micro-plastics seems frequently to be used in a way which includes rather than being distinguished from micro-rubbers.)

They mention PE/PP which I don’t think are found in natural rubber?

This article is making the rounds on news media at the moment without any attention to this, seems a bit suspicious.