Health Canada said graphene is a novel nanomaterial that is reported to have antiviral and antibacterial properties.
However, the advisory issued Friday warns that there is "potential that wearers could inhale graphene particles from some masks," Global News reported.
A preliminary assessment found that these particles had "some potential to cause early lung toxicity in animals."
The potential for humans, however, is unknown, and may "vary based on mask design."
No incidents have yet been reported, but that has not stopped Health Canada from advising that all known distributors, importers and manufacturers stop selling masks containing graphene.
Some of these masks may have been distributed in health care settings, the agency said.
While the full potential health danger is not clear, the agency said the risks associated with the medical devices are "unacceptable," CTV News reported.
"Unless the manufacturers of these masks can provide substantial evidence to support the safe and effective use of graphene-coated masks, Health Canada considers the risk of these medical devices to be unacceptable," Health Canada said.
Health Canada is continuing to study data and requested further information from manufacturers to better assess health risks.