Can someone tell me why microplastics are actually bad? I feel like scientists have recently been discovering they're everywhere, but is there any negative effe

Can someone tell me why microplastics are actually bad? I feel like scientists have recently been discovering they're everywhere, but is there any negative effect? They really are everywhere, and theres nothing we can do now. I bought a Patagonia fleece the other day, and realized the thing is practically made out of microplastics, or 'recycled polyester'. And Patagonia claims to be an eco-friendly company, even though they acknowledge the microplastics problem.