Mask mandates may be gradually easing, but wearing face protection in crowded social settings is likely going to remain commonplace for a while. To combat the environmental strain of single-use disposable face masks, researchers are now exploring ways of giving used masks a new lease of life.
Decontaminating used face masks is one way of extending their lifespan. However, the decontamination technique must also keep the wearer safe, warned Yi Yan Yang, Covering Executive Director at A*STAR’s Institute of Bioengineering and Bioimaging (IBB).
“Repeated exposure to the decontamination methods may affect the integrity of the masks microscopically, which could impair their protective performance,” Yang explained. While there are many commercially-available mask disinfection technologies, little is known about which methods align best with standards set by governing bodies such as the US Centers for Disease Control and Prevention (CDC), and the US Food and Drug Administration (FDA).
To address these gaps, Yang led a team of researchers, and collaborated with the Institute of Materials Research and Engineering (IMRE) and ecosystem partners in a study comparing three common mask disinfection methods: ultraviolet-C (UV-C) irradiation, dry heat and steam sterilisation. Their goal was to identify the strategy that worked best to achieve FDA benchmarks for eliminating specific bacteria, fungi and viruses.
Unlike prior studies examining mask decontamination, Yang’s team investigated microbe-killing efficiencies on both sides of the mask—an important consideration given that different materials are used for the wearer’s side and the outermost layer.
The data revealed that when it comes to mask disinfection, context matters as different technologies work better in different settings. For example, healthcare workers using N95 respirators while caring for patients would likely be exposed to higher levels of infectious agents. Under these high-risk circumstances, five cycles of steam sterilisation of five to 10 minutes each was found to destroy over 99.9 percent of microorganisms on the mask, thereby fulfilling the FDA’s requirements.
To confirm if the masks could still effectively filter bacteria after several rounds of sterilisation, researchers tested samples using an FDA-approved standard method for testing bacterial filtration efficiency called the ASTM F2101-19.
© A*STAR Research
On the other hand, UV-C irradiation was not as effective for decontaminating N95 masks, with a maximum killing efficiency of around 70 percent. However, the researchers showed it to be adequate for sterilising masks worn outside of healthcare settings.
“For members of the public, UV-C irradiation for 10 minutes in a commercially-available UV-C steriliser is a practical method for decontaminating surgical masks, as it is fast and easy to use,” Yang said.
Together, these findings may help to inform national guidelines on mask disinfection best practices as we transition to a new normal.
The A*STAR-affiliated researchers contributing to this research are from the Institute of Bioengineering and Bioimaging (IBB) and the Institute of Materials Research and Engineering (IMRE).
