I have said that from day 1, with my public health experience.
They are effective short term, if there are highly infective vectors that one might come in contact with. Use it, then get out of that area, and dispose.
OTOH, long term use causes you to breath in concentrated expiration pathogens that accumlate on the mask. You literally can make yourself sick with your own mask. This because pathogenic vectors not only can get a foothold by their presence but have a better chance if they are in larger quantities.