Single-use face masks are used globally to mitigate the spread of the ongoing coronavirus pandemic. While this is an effective measure to protect public health, the indiscriminate disposal of the same masks can result in the release of microfibers to the environment. Single-use face masks comprise polypropylene, a common plastic polymer, which shares the same ecological concerns as other types of plastic polymers.  Until now, few studies have shown the release of microfibers from single-use face masks. Also, there is limited knowledge on the effects of the polypropylene microfibers if released into the environment. In this study, we conducted weathering of single-use face masks under simulated environmental conditions to investigate the release of microfibers. The number of fibers released in the presence and absence of UV light was compared. The results reveal that comparable numbers of microfibers were released from both the inner and outer layers of the face masks when floating on moving water. UV exposure drastically increases the number of microfibers released, and it is expected that longer exposure periods combined with mechanical stress (<i>e.g.,</i> vehicle traffic on discarded masks) would lead to important fiber release.  The pristine and weathered microfibers released from the inner and outer layer of the face masks were used in coagulation tests to investigate their removal in wastewater treatment plants (WWTPs). During conventional water treatment (alum combined with polyacrylamide), pristine microfibers have lower removal efficiency (79 - 85%) compared to weathered microfibers (94 - 95%) (statistically significant; p-value &lt; 0.05), but no statistically significant difference was observed in the removal efficiency of fibers from both the inner and outer layers of the masks. Based on these removals, we conservatively estimate the fiber release to natural waters to be &gt; 250 plastic fibers for each discarded mask. If the fibers are directly discharged into natural waters via stormwater sewers (<i>i.e.</i>, no treatment), we estimate that more than 4700 plastic fibers/masks would be released.

Release of fibers from disposable face masks and their fate in aquatic environments

ACS Fall 2021

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