BackgroundThe 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 . MethodsMB 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 {micro}M MB followed by 50,000 lux of broad-spectrum
light or 12,500 lux of red
light for 30 minutes, or with 75{degrees}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 . FindingsOverall, 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. InterpretationMethylene 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 .