The problem is we don't know what "irrelevant amounts" means, which is especially concerning because:

1. Microplastics are pervasive and would be very hard to remediate

2. They seem to bioaccumulate over years, and potentially even transmit intergenerationally

3. We have mechanistic evidence of them interfering with some rather critical biological processes, but processes that would yield chronic issues rather than acute ones

All of this makes it both very important and very difficult to understand the relationship between dosages and possible health effects.