Addressing Personal Protective Equipment (PPE) Decontamination: Methylene Blue and Light Inactivates SARS-CoV-2 on N95 Respirators and Masks with Maintenance of Integrity and Fit
Authors: Lendvay Thomas S. , Chen James , Harcourt Brian H. , Scholte Florine E.M. , Kilinc-Balci F. Selcen , Lin Ying Ling , Lamb Molly M. , Chu Larry F. , Price Amy , Evans David , Lin Yi-Chan , Mores Christopher N. , Sahni Jaya , Kabra Kareem B. , Haubruge Eric , Thiry Etienne , Heyne Belinda , Laperre Jan , Simmons Sarah , Davies Jan M. , Cui Yi , Wagner Thor , Clark Tanner , Smit Sarah J. , Parker Rod , Gallagher Thomas , Timm Emily , Ludwig-Begall Louisa F. , Macia Nicolas , Mackie Cyrus , Hope Karen , Page Ken , Reader Susan , Faris Peter , Jolois Olivier , Patel Alpa , Lemyre Jean-Luc , Molloy-Simard Vanessa , Homdayjanakul Kamonthip , Tritsch Sarah R. , Wielick Constance , Mayo Mark , Malott Rebecca , Willaert Jean-Francois , Nauwynck Hans , Dams Lorène , De Jaeger Simon , Liao Lei , Zhao Mervin , Chu Steven , Conly John M. , Chu May C. 
Published: December 2020

Background

The coronavirus disease 2019 (COVID-19) pandemic has resulted in severe shortages of personal protective equipment (PPE) necessary to protect front-line healthcare personnel. These shortages underscore the urgent need for simple, efficient, and inexpensive methods to decontaminate SARS-CoV-2-exposed PPE enabling safe reuse of masks and respirators. Efficient decontamination must be available not only in low-resourced settings, but also in well-resourced settings affected by PPE shortages. Methylene blue (MB) photochemical treatment, hitherto with many clinical applications including those used to inactivate virus in plasma, presents a novel approach for widely applicable PPE decontamination. Dry heat (DH) treatment is another potential low-cost decontamination method.

Methods

MB and light (MBL) and DH treatments were used to inactivate coronavirus on respirator and mask material. We tested three N95 filtering facepiece respirators (FFRs), two medical masks (MMs), and one cloth community mask (CM). FFR/MM/CM materials were inoculated with SARS-CoV-2 (a Betacoronavirus), murine hepatitis virus (MHV) (a Betacoronavirus), or porcine respiratory coronavirus (PRCV) (an Alphacoronavirus), and treated with 10 µM MB followed by 50,000 lux of broad-spectrum light or 12,500 lux of red light for 30 minutes, or with 75°C DH for 60 minutes. In parallel, we tested respirator and mask integrity using several standard methods and compared to the FDA-authorized vaporized hydrogen peroxide plus ozone (VHP+O3) decontamination method. Intact FFRs/MMs/CM were subjected to five cycles of decontamination (5CD) to assess integrity using International Standardization Organization (ISO), American Society for Testing and Materials (ASTM) International, National Institute for Occupational Safety and Health (NIOSH), and Occupational Safety and Health Administration (OSHA) test methods.

Findings

Overall, MBL robustly and consistently inactivated all three coronaviruses with at least a 4-log reduction. DH yielded similar results, with the exception of MHV, which was only reduced by 2-log after treatment. FFR/MM integrity was maintained for 5 cycles of MBL or DH treatment, whereas one FFR failed after 5 cycles of VHP+O3. Baseline performance for the CM was variable, but reduction of integrity was minimal.

Interpretation

Methylene blue with light and DH treatment decontaminated masks and respirators by inactivating three tested coronaviruses without compromising integrity through 5CD. MBL decontamination of masks is effective, low-cost and does not require specialized equipment, making it applicable in all-resource settings. These attractive features support the utilization and continued development of this novel PPE decontamination method.