Researchers from the University of Cincinnati have shown that two widely available sterilization methods for cleaning disposable surgical masks and N95 respirators make them less effective.
The coronavirus pandemic has caused an explosion in demand for PPE, not only from healthcare workers but also from the general public.
According to Professor Sergey Grinshpun at the University of Cincinnati, this has led some health services to consider sterilizing and reusing single-use masks. The Centers for Disease Control and Prevention has allowed the reuse of N95 respirators, which filter 95 percent of the particles in the air, roughly equivalent to an FFP2 mask, as a crisis capacity strategy.
Grinshpun and colleagues tested two brands of N95 respirators and two types of surgical masks (one with high filtration and one with lower filtration capabilities) using two standard sterilization techniques: autoclaving and soaking in 70% ethanol for two hours. . An autoclave is a device that works similarly to a pressure cooker, applying steam, heat, and pressure to sterilize objects.
“The question for us was: what will happen to the performance of these N95 respirators and surgical masks after they have spent minutes or more in the autoclave and to what extent heat or steam will destroy the filter structure, causing the elements Less useful? “Grinshpun said.
Grinshpun conducted tests in which the PPE was soiled with a protein, using a technique that mimicked a healthcare worker’s breathing, and then sterilized with ethanol or in an autoclave. He repeated this cycle up to five times to simulate the reuse that can occur in a healthcare setting.
He found that while sterilization did not cause visible damage to surgical masks, it did cause damage to the N95 respirator, including disintegration of the sealing material around the nasal clip and loss of elasticity of the strap. The sterilization process also weakens the electrostatic charge on the fibers of surgical masks and N95 respirators, which allow the fibers to capture small particles.
In some cases, this reduced the collection efficiency of N95 respirators below their 95 percent certification level.
“It hardly mattered how often we decontaminated protective devices once, twice, or five times, as the major damage inflicted on the performance characteristics of the items followed the first test,” Grinshpun said.
“You will lose performance if these masks or respirators are sterilized with any of these treatments. Of course, quantitatively, the effect differs for different devices.”
Grinshpun said that instead of relying on autoclaving or ethanol, alternative sterilization techniques, such as the use of UV light, can be explored. The researchers did not analyze UV rays in this study, as they intended to first examine the methods that are available in hospitals.
“We anticipate that UV-based techniques and probably other techniques may be almost as efficient as autoclaving and ethanol in inactivating pathogens, but at the same time would not damage the fibers of the protective devices so that the collection efficiency particle is not affected, “Grinshpun said. “Similar studies can and should be done with alternative decontamination methods.
“The question of how disinfection treatments affect the performance and integrity of respiratory protection devices remains important as long as healthcare workers have to reuse these devices due to their shortage of [PPE]. “
A recent policy document released by the UCL Plastic Waste Innovation Hub estimated that the UK public with reusable masks, such as non-medical fabric masks, could prevent 66,000 tonnes of contaminated plastic waste from being generated each year.
Sign up for the E&T News email to receive great stories like this in your inbox every day.
