In brief

To safely decontaminate masks for reuse, researchers found N95 respirators needed cycles of steam sterilisation, while UV-C irradiation was enough for surgical masks in everyday use.

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Squeaky clean face masks

28 Oct 2022

A head-to-head test of three common mask decontamination methods helps frame standardised national guidelines.

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).

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Teo, J.Y., Kng, J., Periaswamy, B., Liu, S., Lim, P.C. et al. Exploring Reusability of Disposable Face Masks: Effects of Disinfection Methods on Filtration Efficiency, Breathability, and Fluid Resistance, Global Challenges 5:2100030 (2021) | article

About the Researchers

Yi Yan Yang is an Institute Scientist at the Bioprocessing Technology Institute and an Adjunct Professor (Research) at the Department of Orthopaedic Surgery, National University of Singapore. She has over 280 publications in peer-reviewed journals and 70 patents granted, with three patents licensed to two spinoff companies. Her work on antimicrobial polymers was named Scientific American’s 'Top 10 World Changing Ideas' in 2011. In January 2016, she was elected to the American Institute for Medical and Biological Engineering (AIMBE) College of Fellows. In July 2021, she was elected as a Fellow of the Academy of Engineering Singapore. In 2022, she was recognised as a highly cited researcher by Clarivate™.
Jye Yng Teo is a senior research fellow at A*STAR’s Institute of Bioengineering and Bioimaging (IBB). She received her degree in Bioengineering from Nanyang Technological University (NTU), Singapore and obtained her PhD in Chemical Engineering in 2018 from the University of Illinois at Urbana-Champaign (UIUC), USA. She first joined Yi Yan Yang’s team during her PhD studies under the A*STAR-UIUC partnership programme where she developed drug delivery system using polymeric nanoparticles for cancer therapy. She ventured into antimicrobial and antiviral research during her postdoctoral training and now focuses on collaborative projects with the public sector. She has also held an adjunct position with NTU as an assistant professor at the School of Chemistry, Chemical Engineering and Biotechnology since 2021.
Jessica Sze Jia Kng graduated from the National University of Singapore where she majored in Life sciences and minored in Forensic Science. Upon graduation, she worked with Yi Yan Yang for a year on combination cancer drug therapy and contributed to several COVID-19 projects. She then transferred to Kaicheng Liang’s lab as the first staff where she managed the creation of the new lab's infrastructure and capabilities and led the biological efforts that focused on various imaging modalities. These included a non-destructive imaging assay of viability in 2D and 3D cell culture, cell and tissue imaging on a custom fluorescence microscope for clinical applications, and creating preclinical cancer models.

This article was made for A*STAR Research by Wildtype Media Group