Texas A&M Researchers Propose Recycling PPE Through Radiation

Sterilizing used face masks and gowns by exposing them to electron beams could help mitigate the shortage of personal protective equipment.
By Laura Simmons, Texas A&M University College of Engineering July 1, 2020

N95 mask sitting on blue fabric
Radiated face masks are still more effective at filtering particles than homemade masks, researchers say.

Courtesy of David Staack


The COVID-19 pandemic has led to such a shortage of personal protective equipment (PPE) that some health care professionals have resorted to wearing trash bags as makeshift gowns. To mitigate the shortage, Texas A&M University researchers began to study ways to recycle PPE using radiation.

David Staack and Matt Pharr from the College of Engineering and Suresh Pillai from the College of Agriculture and Life Sciences teamed up, using the Food Technology Facility for Electron Beam and Space Food Research and the Plasma Engineering and Non-Equilibrium Processing laboratory on the Texas A&M campus.

Prior to COVID-19, a large portion of Staack’s research focused on medical device sterilization and decontamination. Staack, Pillai and Pharr were working on a similar medical device sterilization project funded by the Department of Energy that identified how polymers and plastics are changed when directly exposed to electron beams or gamma rays. So when the pandemic struck, it wasn’t difficult for the research team to shift their focus to begin sterilizing and recycling PPE including surgical masks and gowns, face shields and N95 respirators.

There are two components of an N95 mask that determine its functionality: filtration and fit. The N95 mask is composed of microscopic pores meant to filter out contaminants such as dust and fumes down to about 0.3 microns. Combined with an electrostatic charge on the non-woven polypropylene fiber for nanoscale particle trapping, the mask is capable of filtering 95 percent of particles 300 nanometers in size, if worn properly. Designed to fit snuggly around the nose, face and chin, the mask can prevent germs from escaping through the sides of the mask when speaking or breathing.

n95 masks in a cardboard box
The Electron Beam Facility could process an estimated 10,000 masks per hour.

Courtesy of David Staack


As part of their research, Staack and his team sent new N95 masks and other PPE through the radiation recycling process at the Electron Beam Facility. While they found that the mechanical properties of the equipment were not damaged and could still be worn appropriately, the N95 mask no longer filtered 95 percent of particles.

“The radiated masks ended up going from filtering 95 percent of particles 300 nanometers in size to only filtering between 50 percent and 60 percent of particles a few hundred nanometers in size,” said Staack, the Sallie and Don Davis ’61 Career Development Professor in Mechanical Engineering. “That’s still a lot better than a homemade mask made from a T-shirt.”

Additionally, some of the electrostatic filtration of the N95 mask is lost from a day of wear, hence their disposable nature. And while the best option is to immediately reach for a brand-new mask each day, pandemics like ones caused by COVID-19 can quickly lead to a stark shortage in PPE for health care professionals.

Ideally, a hospital would box up its used PPE and send it to a radiation facility to be recycled, rather than disposing of them. The Electron Beam Facility is divided in half; one side is designated for contaminated equipment and the other is for clean equipment post-recycling. If the hospital was local, a delivery truck would arrive at the facility’s loading dock on the contaminated side. The boxes of PPE would be loaded onto a conveyer belt moving at three feet per minute and be transported throughout the facility to be radiated.

The box would pass under a 10-million-electron volt beam that would radiate the box with a dose of 25 kilojoules per kilogram – a typical Food and Drug Administration-recommended (FDA) dose for medical device sterilization. This would completely sterilizes anything on or within the box by breaking DNA and RNA bonds, preventing any living organism from reproducing. The box would the travel to the clean side of the facility, where a new truck would transport the treated material back to the hospital it came from for the PPE to be redistributed.

Electron beam irradiation is a common, proven and FDA-approved method of medical device sterilization. Irradiation by electron beam, gamma and X-ray methods account for approximately 50 percent of the market of all medical devices sterilized worldwide. The Electron Beam Facility is already equipped for industrial use, and based on Staack’s research, is able to process and recycle 10,000 masks an hour.

“There’s still some logistical issues we’re working through,” Staack said. “Can we do it safely? Can masks be distributed to someone other than the original user? These are the questions we’re researching now so that if something happens in the short term like another wave of COVID-19, we’re ready. And if something happens in the long term, we’re more knowledgeable about it.”

There are approximately 50 to 100 electron beam facilities in the United States alone. Staack’s goal is to be able to share the team’s results and distribute this critical information around the world so that everyone is better equipped to tackle a global pandemic.

This article by Laura Simmons originally appeared on the College of Engineering website.

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