Medical supplies such as gloves and syringes are often sterilized using radiation, however the method has been found unsuitable for sanitizing worn respiratory face masks. (Photo: L. Potterton/IAEA)
Radiation is an effective and established tool to sterilize personal protective equipment (PPE) that is in high demand during the COVID-19 pandemic, except for respiratory face masks as it weakens their filters, the International Atomic Energy Agency (IAEA) said today.
While radiation is not recommended to sanitize certain types of used masks for hospital staff, the IAEA encourages Member States to continue to irradiate other PPE for sterilization prior to their use, including surgical masks and gloves.
Upon request from several countries, the IAEA reviewed findings from five institutions that tested the use of ionizing radiation - gamma and electron beams - to sterilize used respiratory masks, such as models N95 and FFP2 commonly worn by medical personnel. As numbers of COVID-19 infections increase, shortages in protective equipment for staff on the frontline of the pandemic continue to pose a problem in many countries.
"Many governments are looking to expand the availability of PPE by sterilizing them with chemicals, UV light or radiation," said Celina Horak, Radiation Processing Specialist at the IAEA. "Face masks are of particular interest, as they are indispensable for hospital staff but also used among the general population for protection while shopping or using public transport."
Respiratory face masks are important for health workers, as they contain filters that block small external particles and droplets. These include N95 and FFP2 masks, which filter out at least 95 per cent of external airborne particles. These differ from surgical masks, which for the most part only guard others against the wearer's own respiratory emissions.
Tests carried out by institutes in France, Israel, Republic of Korea, Poland, and the United States showed that the level of radiation required to sterilize respiratory face masks decreased their filtering performance.
"The masks showed no significant changes in fit or measurable structural changes when exposed to the 24 kGy dose of radiation needed to kill viruses and bacteria, but filtering capacity was significantly compromised," said Byungnam Kim, head of the irradiation facilities at the Advanced Radiation Technology Institute of the Korea Atomic Energy Research Institute, which carried out tests using electron beams.
Similar results were obtained by the ARC-Nucleart Laboratory in France for the common European model. "In FFP2 masks, which include an electrostatic filter, results clearly showed that gamma radiation degrades the filtering performance, even at lower doses," said Laurent Cortella, senior researcher at the Laboratory.
Radiation sterilization is used since the late 1950s to eliminate microorganisms, such as bacteria, viruses, fungi and spores, from medical equipment. Currently, almost 50 per cent of healthcare products, such as gloves, syringes and single use protective clothing, are sterilized using gamma rays, electron-beams or X-rays prior to their use.
The use of radiation has, in some countries, been extended to disinfect alternative types of community protection items before their use, such as cloth masks which offer some protection. In Brazil, the Nuclear and Energy Research Institute (IPEN) is using radiation to sterilize textile masks produced by local seamstresses. "Even at a lower dose, radiation is very effective in eliminating microorganisms that may have been introduced during the production process," said Pablo Vasquez, senior researcher at IPEN, adding that the Institute is treating 50,000 of these masks for distribution during the pandemic.
The IAEA promotes industrial applications of radiation, such as the sterilization of medical equipment and food, among its Member States, helping countries through training, expert advice and research.
