As in all matters, never, I repeat, never be interviewed by the police or in this case health department persons. Tell them you are a great friend of the police, the department of health or whatever, but do not answer any question other than providing identification.
It is virtually impossible for an enforcement person to prove you are not exempt from the mask requirement due to your health, activity or destination other than your answer to their questions:
“Anton, do you have a respiratory illness that prevents you from wearing a mask? Uh, no.”
Wrong answer. They cannot get your medical records.
The answer is, "You may not ask me that question". If you really want to gild the lily you can say, "I am sorry but my answering that question would mean that I helped you violate the ADA and I do not want to get you into legal trouble."
Of course talking to the police in the first place is a no no.
There are only five things you can say to the police.
1.)Am I free to leave? (if they say yes then leave)
2.) Am I under arrest? (If the answer is no then ask the first question.)
3.) Do you have a warrant?
4.) May I see the warrant?
5.) I wish to consult with my attorney before answering any questions.
6.) No comment.
Ok maybe seven things.