Many efforts to reduce transmission of diseases like COVID-19 and the flu have focused on measures such as masking and isolation, but another useful approach is reducing the load of airborne pathogens through filtration or germicidal ultraviolet light. Conventional UV sources can be harmful to eyes and skin, but newer sources that emit at a different wavelength, 222 nanometers, are considered safe.
The findings are reported in the journal Environmental Science & Technology, in a paper by recent MIT postdoc Victoria Barber, doctoral student Matthew Goss, Professor Jesse Kroll, and six others at MIT, Aerodyne Research, and Harvard University.
While Kroll and his team usually work on issues of outdoor air pollution, during the pandemic they became increasingly interested in indoor air quality. Usually, little photochemical reactivity happens indoors, unlike outdoors, where the air is constantly exposed to sunlight. But with the use of devices to clean indoor air using chemical methods or UV light, “all of a sudden some of this oxidation is brought indoors,” triggering a potential cascade of reactions, Kroll says.
Initially, the UV light interacts with oxygen in the air to form ozone, which is itself a health risk. “But also, once you make ozone, there’s a possibility for all these other oxidation reactions,” Kroll says. For example, the UV can interact with the ozone to produce compounds called OH radicals, which are also powerful oxidizers.
Barber, who is now an assistant professor at the University of California at Los Angeles, adds, “If you have volatile organic compounds in the environment, which you do basically in all indoor environments, then these oxidants react with them and you make these oxidized volatile organic compounds, which in some cases turn out to be more harmful to human health than their unoxidized precursors.”
The process also leads to the formation of secondary organic aerosols, she says. “Again, this stuff is harmful to breathe, so having it in your indoor environment is not ideal.”
The formation of such compounds is particularly problematic in the indoors, Kroll says, because people spend so much of their time there, and low ventilation rates can mean these compounds could accumulate to relatively high levels.
Having studied such processes in outdoor air for years, the team had the right equipment in hand to observe these pollution-forming processes indoors directly. They carried out a series of experiments, first exposing clean air to the UV lights inside a controlled container, then adding one organic compound at a time to see how they each affected the compounds that were produced. Although further research is needed to see how these findings apply to real indoor environments, the formation of secondary products was clear.
The devices that make use of the new UV wavelengths, called KrCl excimer lamps, are still relatively rare and expensive. They’re used in some hospital, restaurant, or commercial settings rather than in homes. But while they have sometimes been touted as a substitute for ventilation, especially in hard-to-ventilate older buildings, the new study suggests that’s not appropriate.
“Our big finding was that these lights are not a replacement for ventilation, but rather a complement to it,” says Kroll, who is a professor of civil and environmental engineering, and of chemical engineering.
Some have proposed that with these devices, “maybe if you could just deactivate the viruses and bacteria indoors, you wouldn’t need to worry about ventilation as much. What we showed is that, unfortunately, that’s not necessarily the case, because when you have less ventilation, you get a buildup of these secondary products,” Kroll says.
He suggests a different approach: “There may be a sweet spot in which you’re getting the health benefits of the light, the deactivation of pathogens, but not too many of the disbenefits of the pollutant formation because you’re ventilating that out.”
The results so far are from precisely controlled lab experiments, with air contained in a Teflon bag for testing, Barber points out. “What we’re seeing in our bag is not necessarily directly comparable to what you would see in a real indoor environment,” she says, “but it does give a pretty good picture of what the chemistry is that can happen under radiation from these devices.”
Goss adds that “this work allowed us to validate a simple model that we could plug in parameters to that are more relevant to actual indoor spaces.” In the paper, they use this information “to try to apply the measurements we’ve taken to estimate what would happen in an actual indoor space.” The next step in the research will be to attempt follow-up studies taking measurements in real-world indoor spaces, he says.
“We’ve shown that these are a potential concern,” Kroll says. “But in order to understand what the full real-world implications are, we need to take measurements in real indoor environments.”
“These 222-nanometer radiation devices are being deployed in bathrooms, classrooms, and conference rooms without a full accounting of the potential benefits and/or harm associate with their operation,” says Dustin Poppendieck, a research scientist at the National Institute for Standards and Technology, who was not associated with this study.
“This work lays the foundation for a proper quantification of potential negative health impacts of these devices. It is important this process is completed prior to relying on the technology to help prevent the next pandemic.”
More information: Victoria P. Barber et al, Indoor Air Quality Implications of Germicidal 222 nm Light, Environmental Science & Technology (2023). DOI: 10.1021/acs.est.3c05680
Journal information: Environmental Science & Technology
News
Ethics in Nanomedicine: Key Issues and Principles
Nanomedicine, a branch of nanotechnology, is revolutionizing healthcare by enabling the manipulation of materials at the nanoscale to diagnose, treat, and prevent diseases. Unlike traditional treatments, nanoparticles (NPs) are highly precise in targeting diseased [...]
A call for robust H5N1 influenza preparedness and response
As the global threat of H5N1 influenza looms with outbreaks across species and continents including the U.S., three international vaccine and public health experts say it is time to fully resource and support a [...]
Mucosal COVID-19 boosters outperform mRNA shots in preventing upper airway infections
In a recent study published in Nature Immunology, a team of researchers from the United States used non-human primate models to compare the protection conferred by an intramuscular booster dose of the bivalent messenger ribonucleic acid [...]
How Space Travel Really Changes Astronauts – From the Inside Out
International team reveals previously unknown effects on physiology that could shape the future of long-duration space missions. Researchers have discovered significant changes in the gut microbiome due to spaceflight, which affects host physiology and [...]
Breakthrough in blood stem cell development offers hope for leukemia and bone marrow failure
Melbourne researchers have made a world first breakthrough into creating blood stem cells that closely resemble those in the human body. And the discovery could soon lead to personalized treatments for children with leukemia [...]
Scientists Develop Game-Changing Needle-Free COVID-19 Intranasal Vaccine
A new mucosal COVID-19 vaccine poised to revolutionize the delivery process is especially beneficial for those with a fear of needles. A next-generation COVID-19 mucosal vaccine is set to be a game-changer not only when delivering [...]
Scientists Develop All-in-One Solution To Catch and Destroy “Forever Chemicals”
A new water treatment system developed by UBC researchers efficiently removes and destroys PFAS pollutants using a dual-action catalyst, offering a sustainable and cost-effective solution for water purification challenges. Chemical engineers at the University of [...]
New method accelerates drug discovery from years to months
Researchers from the University of Cincinnati College of Medicine and Cincinnati Children's Hospital have found a new method to increase both speed and success rates in drug discovery. The study, published Aug. 30 in [...]
A new smart mask analyzes your breath to monitor your health
Your breath can give away a lot about you. Each exhalation contains all sorts of compounds, including possible biomarkers for disease or lung conditions, that could give doctors a valuable insight into your health. [...]
Study reveals the role of blood clotting in COVID-19
In a study that reshapes what we know about COVID-19 and its most perplexing symptoms, scientists have discovered that the blood coagulation protein fibrin causes the unusual clotting and inflammation that have become hallmarks [...]
A Novel Cancer Vaccine Combining Nano-11 and ADU-S100
In a recent article published in npj Vaccines, researchers detailed the development of a novel cancer vaccine that combines a plant-derived nanoparticle adjuvant, Nano-11, with a clinically tested STING agonist, ADU-S100. The primary objective was [...]
AI spots cancer and viral infections with nanoscale precision
Researchers have developed an artificial intelligence which can differentiate cancer cells from normal cells, as well as detect the very early stages of viral infection inside cells. The findings, published today in a study [...]
Tiny shards of plastic are increasingly infiltrating our brains, study says
Human brain samples collected at autopsy in early 2024 contained more tiny shards of plastic than samples collected eight years prior, according to a preprint posted online in May. A preprint is a study which has not yet [...]
Scientists Have Discovered Strange DNA in Our Brains – and It Could Be Shortening Our Lives
According to the research, these mitochondrial DNA insertions could be linked to early death. Mitochondria in brain cells frequently insert their DNA into the nucleus, potentially impacting lifespan, as those with more insertions were found to [...]
Watch Out After a Hospital Stay: You Could Be Exposing Your Family to Superbugs
Research indicates hospitals contribute to the local spread of antibiotic-resistant infections. A recent study published in the journal Infection Control & Hospital Epidemiology by the Society for Healthcare Epidemiology of America suggests that family members of [...]
Molecular Trickery: How COVID-19 Silently Sabotages the Human Immune System
Researchers have discovered that SARS-CoV-2 manipulates the human immune system by forcing cells to produce non-functional proteins, hindering the body’s antiviral defenses. This groundbreaking study by teams from prestigious Brazilian universities highlights potential targets for new COVID-19 treatments, [...]