As a consequence of the COVID-19 pandemic, billions of
people wear
face masks for hours on a daily basis. However, whether hazardous
materials released from the face masks might pose potential risks
to human health remains mostly unexplored. In particular, nanoparticle-containing
face masks have become popular in the market due to their improved
antiviral and antibacterial effects. The leachability of nanoparticles
and any subsequent toxicity are largely unknown. This study is the
first to evaluate the Cu leachability from a face mask containing
Cu nanoparticles and the subsequent cytotoxicity of the leachate.
We showed that ∼20 μg of Cu in the mask was inhaled,
accounting for almost 3% of the total Cu. Moreover, 30–40%
of the Cu attached to fibers from the mask could be easily released
into solution, and most of the released Cu existed in ionic forms.
Cell-based testing indicated that although the leachate did not induce
any cytotoxicity, it caused significant Cu stress leading to the exocytosis
of lysosomes, changes in glutathione concentration, and the generation
of reactive oxygen species. Overall, our results suggest that the
leachability of nanoparticle-containing face masks should be carefully
assessed, especially considering that most nanoparticle-containing
face masks are recommended to be reusable after being washed.