UV sterilization of masks

clean masksDuring the global COVID-19 pandemic, the sudden and overwhelming demand for protective masks exceeded the supply. As cases of COVID-19 have been rising again, wearing a mask continues to be one of the most effective ways to reduce the risk of viral transmission in crowded indoor spaces with poor ventilation. But do masks come with a cost? The answer is yes!

“Reports indicate that the single use and disposal of millions of masks during the pandemic have contributed to microplastics effluence causing damage to the environment, animals, and even human cells,” explains John Gibson, a postdoctoral fellow in U of T’s Department of Chemical Engineering & Applied Chemistry. “One way to increase mask supply and reduce its subsequent pollution is to sterilize them for reuse using UV light.”

Although many researchers have shown that UV light can be used for sterilization of materials, very few have provided a framework that can make predictions about how a complex material, such as a face mask, will respond to UV light and hence sterilization. To address this challenge, a team led by Professor Ramin Farnood and involving Housyn Mahmoud, Gibson, Ted Mao (ChemE MASc 8T3, PhD 9T7), and Conrad Obegaard devised and validated a novel and practical approach to estimate the UV-light propagation inside face masks.

“There are numerous advantages of UV sterilization for masks. Specifically, mask performance and fit remain intact, there’s no residual toxicity, it’s fast-acting, and readily available. Our research provides a model that can be used to make predictions about virtually any multi-layered material, including masks,” elaborates Gibson.

Masks have always been a superior disease prevention tool. They were important long before the pandemic, and will continue to be vital. It is simply good practice to wear a mask to protect yourself and others when in a high-risk situation. The research by Professor Farnood’s team provides a way of making this practice sustainable. Their paper, Generalized Kubelka’s Theory for Light Transmission in Multi-layer Materials and Its Application for UV Light Penetration in Filtering Facepiece Respirators, was released in the Journal of Biophotonics this month.


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