Much more in depth NIH article (go to section 3)
We are definitely NOT in theory territory here, there have been studies and reports of people directly suffering from the effects of PFAS, what we are not clear on is how it’s interacting with our bodies.
I know you’re looking for on or over ear, but for the gym, it might make more sense to get the non TWS earbuds like the LG Tone or similar. They’re light in your ear as all the battery weight stays on your neck.