The ONLY ‘science’ I am aware of etc is that though I do wear around my neck (just so I can say I have it on), once my nose and mouth are covered, I suffer SEVERE respiratory problems...
If approached, I will not argue with the person telling me but mention my respiratory problem and have yet to be challenged.
I do plan on asking to speak to manager if the ‘checker’ persists and again, not argue, just ask them if they are aware of ADA etc.
I fondly recall being considered a social pariah when I ‘demanded/requested’ people keep an arms length from me.
My, how times have changed...
“I do wear around my neck (just so I can say I have it on)”
I wrap the two elastic thingies around my wrist so I can truthfully say I’m wearing a face mask. But I never wear one on my face, and nobody has said a word. (Except in a medical office.)