The gunk that accumulates on the inside of the mask generally isn't a huge threat so long as you only wear it for 2 hours. Think of it like food safety. You wouldn't leave a cooked meal out for longer than 2 hours. Masks should be treated the same.
That said, masks also should only be worn by symptomatic people (and of course some healthcare worker situations, but that's a distraction from the topic).
The gunk that accumulates on the inside of the mask generally isn't a huge threat so long as you only wear it for 2 hours. Think of it like food safety. You wouldn't leave a cooked meal out for longer than 2 hours. Masks should be treated the same.
That said, masks also should only be worn by symptomatic people (and of course some healthcare worker situations, but that's a distraction from the topic).