Single-Use Face Masks as a Potential Source of Synthetic Antioxidants to the Environment

Single-use face masks are a powerful tool for reducing the spread of COVID-19. The usage of single-use face masks has increased enormously since the start of the COVID-19 pandemic, and pollution from the huge volume of discarded single-use face masks may become an environmental issue. This study focuses on synthetic antioxidants (AOs), including synthetic phenolic antioxidants (SPAs) and organophosphite antioxidants (OPAs), used in single-use three-layer face masks. Both SPAs and OPAs were detected in single-use face masks, with total concentrations ranging from 20.0 to 575 μg/g (median of 175 μg/g). The dominant congeners detected in the face masks were tris(2,4-di-tert-butylphenyl) phosphite (AO168, median of 83.2 μg/g), tris(2,4-di-tert-butylphenyl) phosphate (AO168O, median of 72.9 μg/g), and pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (AO1010, median of 13.7 μg/g). No significant concentration difference was observed between medical and nonmedical face masks. Among the three different layers of the face masks, the middle layers showed the highest AO concentrations. On the basis of the median concentrations detected, we estimate that 1084 tons of AOs is used in face masks annually, suggesting that discarded face masks may be a source of AOs to the environment. This is the first study to report the occurrence of a wide range of AOs in face masks.