With cold and flu season rapidly approaching, public health officials worry about a resurgence of COVID-19 and personal protective equipment shortages. Protecting frontline workers will likely include decontaminating face masks.
A spike in COVID-19 cases this fall and winter could leave healthcare facilities with renewed shortages of personal protective equipment — particularly masks.
Hundreds of frontline healthcare workers have died from the virus since the pandemic struck in China in 2019, bringing the need for effective face masks into sharp relief. But despite the efforts of 3M and other companies worldwide to boost production of the most effective filtering masks — N95s — there still might not be enough.
N95s, which filter out 95% of airborne particles, were designed for industrial use; for medical use, they should be discarded after every patient encounter, according to the Centers for Disease Control and Prevention (CDC). But pandemic-induced shortages have forced healthcare providers to wear the same mask for full shifts and for hospitals and clinics to seek ways to reuse them.
A number of researchers have studied the efficacy of mask decontamination systems. As of September 4, the FDA had granted emergency use authorizations (EUAs) for 10 decontamination systems, nine of which use vaporized hydrogen peroxide (VHP) and one that uses supercritical carbon dioxide — a fluid/gas combination created by pressurization.
The National Institute of Occupational Safety and Health (NIOSH) has also said that ultraviolet germicidal irradiation, VHP and moist heat have shown the most promise. Other methods under study include peracetic acid and ethylene oxide.
Medical Design & Outsourcing talked to a researcher who recently studied mask decontamination methods for effectiveness in killing the virus and in not damaging masks or their straps. Co-lead investigators Dr. Anand Kumar, an infectious disease and critical care specialist at the University of Manitoba’s Health Sciences Center, and Jay Krishnan, senior biosafety officer at the National Microbiology Laboratory of the Public Health Agency of Canada in Winnipeg, studied seven possible decontamination methods. The researchers have submitted the study for publication.
“The study basically demonstrates which methods might be most effective and easily implemented,” Kumar said in an interview. “We basically found that a couple of them were particularly strong, and a couple that we had hoped would work didn’t.”
Their conclusions: The best and most practical method is the application of moist heat at about 70 °C (158 °F) for an hour or so at about 25% humidity, which helps kill the pathogen. Moist heat decontamination can easily be done in bulk, leaves no chemical residue that would require extra aeration time. It can even be performed in hospital blanket heaters, Kumar posited.
“Most can be adjusted to 70 degrees, and if you put a large pan of water in it, you’d hit 22% humidity,” he explained. “That means you can do it in any ward in North America. Most of them have these blanket heaters.”
Vaporized hydrogen peroxide is not as easily accessible, but the researchers found it to be effective. Peracetic acid fogging also worked well.
“It’s not routinely used in most places, but it is a technique that can be quite easily performed,” Kumar said of peracetic acid. “You can set up to do it quite easily.”
Ethylene oxide, which is widely used to sterilize medical devices, also worked well, but required 24-hour aeration to eliminate toxins. “Between the toxicity and the long cycle time, I don’t think it’s really practical,” Kumar said.
Ultraviolet light (UVC), which has been touted as an effective decontaminant, failed in the Winnipeg study.
“If you actually do the decontamination as suggested by some other groups and dissect the mask, you would find a fair amount of virus still there,” Kumar said. “The ultraviolet light does not penetrate through the multiple layers of most of these kinds of masks.”
Educational institutions including Duke University have received EUAs to set up mask decontamination equipment in dedicated spaces. Michigan State University’s Animal Care Program received one of the most recent EUAs for this purpose in July.
The animal care program in Lansing, Mich., had used vaporized hydrogen peroxide for years to decontaminate rooms between uses by different animals and projects, according to Dr. F. Claire Hankenson, a veterinarian, director of campus animal resources and a professor of pathobiology and diagnostic investigation. On March 31, Michigan’s governor and the university president contacted the veterinary center to ask if staff would consider mask decontamination.
Hankenson co-authored a study on the efficacy of vaporized hydrogen peroxide (H2O2) to decontaminate masks in an unused 20,000 ft2 building. H2O2 was delivered to rooms using robotic HaloFoggers, dispersing H2O2 vapor and increasingly concentrated microdroplets as a fog for a timed period based on cubic footage of rooms.
Published in May in Applied Biosafety, the journal of the Association for Biosafety and Biosecurity, the peer-reviewed study determined that it’s possible to clear a variety of N95 respirator types and sizes of potential bacterial and viral agents using VHP in a controlled fog/dwell/exhaust cycle.
Hankenson described how it works: After the prepared masks are loaded in the rooms, the VHP decontamination cycle takes six hours. Once complete and effectiveness is verified, the equipment is packaged and picked up by staff from participating healthcare and first responders’ facilities. The process is designed to reduce the possibility of cross-contamination and ensure each piece of equipment is returned to the original user.
The Michigan State system can decontaminate up to 7,000 respirators daily, which the authors wrote “will address the predicted surge of COVID-19 cases in the state, and ultimately allow each respirator to be reused multiple times. There is no other public site in the region with our capacity to offset the continued supply chain issues for PPE needs.”
In addition to helping keep frontline healthcare workers and first responders safe from COVID-19, Hankenson hopes the decontamination program will save users money. She has found that prices for N95 masks can range as high as $5 apiece, but the Animal Care system will be able to recycle them for about 25 cents each.
“The most gratifying thing was just this incredible coming together of experts who were interested in doing whatever they could to help the community,” Hankenson added. “It was incredibly rewarding to work with everybody.”