New study shows that gaseous ozone, a highly reactive chemical made up of three oxygen atoms, could provide a safe way to disinfect certain types of personal protective equipment that are in high demand to protect healthcare workers from Covid -19.
Conducted by researchers at the Georgia Institute of Technology using two pathogens similar to the novel coronavirus, the study found that ozone can inactivate viruses on items such as Tyvek gowns, polycarbonate face shields, eye protection. and respiratory masks without damaging them – as long as they do not include the elastic straps stapled.
The study found that the consistency and effectiveness of ozone treatment depended on maintaining a relative humidity of at least 50% in the chambers used for disinfection.
Ozone is one of the friendliest, cleanest ways to deactivate viruses and kill most pathogens. It leaves no residue; it is easy to generate from atmospheric air and is easy to operate from an equipment point of view. “
MG Finn, lead study author and chair, Georgia Tech’s School of Chemistry and Biochemistry
The research results are described in an article published on the medRxiv preprint server and will be submitted to a journal for peer review and publication.
Ozone can be produced with inexpensive equipment by exposing atmospheric oxygen to ultraviolet light or by an electrical discharge such as a spark.
During local and regional peaks of coronavirus infection, PPE shortages may force hospitals and other health facilities to reuse PPE that was intended for single use.
Healthcare facilities have used ultraviolet light, vaporized hydrogen peroxide, heat, alcohol, and other techniques to disinfect these items, but until recently ozone disinfection for PPE did not hadn’t generated much interest, said Finn, who also owns the James A. Carlos. Family chair for pediatric technology.
Ozone is widely used to disinfect wastewater, purify drinking water, sanitize food, and disinfect certain types of equipment, even clothing.
Ozone disinfection cabinets are commercially available that take advantage of the oxidative effects of the gas to kill bacteria and inactivate viruses.
âThere was no reason to think it wouldn’t work, but we couldn’t find any examples of testing a variety of personal protective equipment,â Finn said.
âWe wanted to help meet the needs of hospitals and other health organizations to show that this technique could work against pathogens similar to the coronavirus. “
Phil Santangelo, a virologist in Wallace H. Coulter’s Department of Biomedical Engineering, recommended two respiratory viruses – influenza A and respiratory syncytial virus (RSV) – as surrogates for coronavirus.
Both are known as “enveloped” viruses because, like the coronavirus, they are surrounded by an outer lipid membrane. Influenza and RSV are less dangerous than the SARS-CoV-2 coronavirus, allowing Georgia Tech researchers to study them without high-containment laboratory facilities.
Santangelo, Finn and their team designed a test procedure in which solutions containing both viruses were placed on samples of the PPE materials under study.
The solutions were allowed to dry before the samples were placed in a chamber into which ozone was introduced at varying concentrations as low as 20 parts per million.
After treatment for varying durations, the researchers tested the PPE samples to determine whether or not any of the viruses on the treated surfaces could infect cells grown in the lab. The whole test procedure took about a day and a half.
âThe protocol that we have put in place is very sensitive to whether or not the virus can reproduce itself, and we have found that ozone has been very successful in rendering them harmless,â said Finn.
âOxidation of biological samples to a significant extent is sufficient to inactivate a virus. The genetic material or the outer envelope of the virus would be damaged enough so that it can no longer infect a host cell. “
Loren Williams, professor in the School of Chemistry and Biochemistry, introduced the research team to a manufacturer of ozone disinfection chambers, which allowed the equipment to be evaluated using the protocol of test.
During the test, the researchers learned that sufficient relative humidity in the chamber – at least 50% – was essential to quickly inactivate viruses in a consistent manner.
After subjecting the face masks and respirators to ozone disinfection, the team worked with Associate Professor Ng Lee (Sally) Ng of the School of Chemical and Biomolecular Engineering to assess the filtration capabilities of the items.
The ozone treatment did not appear to adversely affect the N-95 filter material.
While the ozone did not affect the filtration ability of the masks, it did damage the elastic materials used to hold the masks together.
Although elastic bands can be removed from masks during ozone disinfection, their removal and replacement on a large scale can make the ozone treatment technique impractical.
Otherwise, however, ozone may offer an alternative technique for disinfecting other types of PPE.
âOzone would be a viable method for hospitals and other organizations to disinfect clothing, goggles and gloves,â Finn added.
“It is inexpensive to produce, and we hope that by sharing information about what we have found, healthcare facilities can see it as an option, especially in low-resource areas of the world.”
Georgia Institute of Technology