Face masks worn by the public are not regulated, and some fall short of standards of medical PPE. Certain types of masks which are readily available to the public during the coronavirus pandemic were found to cause dangerous levels of exposure to chemicals if worn for long enough. Analysis from the Hamburg Environmental Institute, which was obtained by Ecotextile News, revealed a plethora of face masks contained levels of formaldehyde and fluorocarbons.
https://www.express.co.uk/news/science/1418012/face-masks-coronavirus-covid-19-guidelines-ppe-evg