I have absolutely no in-depth scientific understanding of the topic, and tend to be wary of any sort of panic-inducing press releases and such, so have no idea of the validity of the concerns, methodologies, etc.
Here’s something from the CDC:
It sounds like, yes, they are present but they don’t know what levels present a problem. Like many thing the dangerous levels may be far, far more than the average human will ever experience. But a good thing to be aware of…and follow.