Canada has prohibited the use of face masks containing graphene due to the possibility of risks from inhalation of particles.
Health Canada announced on Friday that it has "directed all known distributors, importers and manufacturers to stop selling and to recall the affected products".
The department is currently in the midst of a scientific assessment of the graphene and biomass graphene masks even as it initiated "the precautionary approach of withdrawing them from the market while continuing to gather and assess information".
Graphene is a novel nanomaterial, comprising minute particles, which has been touted as having "anti-viral and anti-bacterial properties".
According to a report in September last year, researchers at the City University of Hong Kong claimed that such masks could help in countering coronaviruses.
However, Health Canada said that its "preliminary assessment of available research identified that inhaled graphene particles had some potential to cause early lung toxicity in animals".
That assessment came after the department was made aware that "masks containing graphene have been sold with Covid-19 claims and used by adults and children in schools and daycares" and "may also have been distributed for use in healthcare settings".
While the recall was announced on Friday, such masks, manufactured using nanotechnology, remain widely available in Canada, and in India.
While the effect of inhalation of the microscopic particles in humans is still being studied, Health Canada said that it has "requested data from mask manufacturers to assess the potential health risks related to their masks that contain graphene".
Health Canada added that it has written to provinces and territories advising them to "stop distribution and use of masks containing graphene" while the department "will continue to take appropriate action to stop the import and sale of graphene face masks."