Improper Use of UV Germicidal Lamps May Generate Indoor Air Pollutants

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MIT Research Reveals Improper Use of UV Germicidal Lamps May Generate Indoor Air Pollutants

MIT Research Reveals Improper Use of UV Germicidal Lamps May Generate Indoor Air Pollutants

Although ultraviolet light can effectively kill pathogens, including SARS-CoV-2, it might trigger unnecessary chemical reactions, emphasizing the need for proper ventilation during its use.

Many efforts to reduce the spread of diseases like COVID-19 and the flu focus on measures like masking and isolation, but an alternative method involves reducing the pathogen load in the air through filtration or UV germicidal lamps.

Traditional UV light sources can pose risks to the eyes and skin, but novel light sources emitting at a different wavelength (222 nanometers) were previously deemed safe.

Improper Use of UV Germicidal Lamps May Generate Indoor Air Pollutants

Recent research from MIT, however, indicates that these UV lamps could potentially produce harmful compounds indoors. While researchers emphasize this doesn’t imply a complete avoidance of these lamps, they do stress the necessity for appropriate UV intensity in specific indoor environments and its use alongside proper ventilation.

MIT postdoctoral fellow Victoria Barber, doctoral student Matthew Goss, Professor Jesse Kroll, along with six other scholars from MIT, Aerodyne Research, and Harvard University, published their findings in the journal “Environmental Science and Technology.”

Kroll and his team typically study outdoor air pollution issues but have increasingly focused on indoor air quality during the pandemic. Unlike outdoors where sunlight exposure is frequent, indoor spaces usually witness minimal photochemical reactions. However, the use of chemical methods or UV air purification devices suddenly introduces “some of these oxidation reactions indoors,” according to Kroll.

Initially, UV reacts with oxygen in the air, forming ozone, a health risk in itself. “But once you make ozone, there is the possibility for other oxidation reactions. For example, UV can interact with ozone to produce compounds called OH radicals, which are powerful oxidants,” Kroll stated.

Barber, now an assistant professor at the University of California, Los Angeles, added, “If there are volatile organic compounds in the environment (which are present in almost all indoor environments), these oxidants will react with them, forming these oxidized volatile organic compounds, which in some cases can be more harmful to human health than the unoxidized precursors.” This process also leads to secondary organic aerosols, which are harmful for respiration, making their presence indoors less than ideal.

Kroll highlighted the indoor formation of these compounds as a concern due to prolonged indoor stays and lower ventilation rates, potentially leading to the accumulation of these compounds to relatively high levels.

After years of studying similar processes in outdoor air, the research team employed suitable equipment to directly observe these pollution formation processes indoors. Through a series of experiments, they exposed clean air in a controlled container to UV light and introduced various organic compounds, observing their impact on the resulting compounds. While further research is necessary to understand how these findings apply to real indoor environments, the formation of these secondary products was evident.

Devices using the new UV wavelength, namely KrCl excimer lamps, remain rare and expensive, primarily used in hospitals, restaurants, or commercial spaces, not households. Although these devices have been hailed as ventilation alternatives, particularly in poorly ventilated old buildings, the new research suggests they don’t replace ventilation but act as a complement.

“It was a significant finding for us that these lamps aren’t a replacement for ventilation but rather a supplement to it,” Kroll mentioned. “Some people might think that with these devices, you could deactivate viruses and bacteria indoors and not worry about ventilation issues. Unfortunately, our research shows that when ventilation is reduced, these secondary reaction products can accumulate.”

He suggested a different approach to use these disinfection devices: “There might be a sweet spot where you can get the benefits of the light for health and pathogen deactivation without too many adverse effects from the pollutants because you’re exhausting those pollutants out through ventilation.”

Barber noted that so far, these results stem from precisely controlled lab experiments where air was enclosed in Teflon bags. “What we see in the bag might not be directly comparable to what you’d see in a real indoor environment, but it gives a good description of the chemical reactions that might occur under the radiation from these devices.”

Goss added, “This work allowed us to validate a simple model where we can input parameters more relevant to real indoor spaces. In the paper, they used this information to “try to apply what we measured to estimate what might happen in actual indoor spaces.” The next step in the research will involve attempting to measure these effects in real indoor environments.

Kroll stressed, “These are all potential issues we’ve demonstrated. But to understand the full impact in the real world, we need to measure in real indoor environments.”

Dustin Poppendieck, a research scientist at the National Institute of Standards and Technology, who was not involved in the study, said, “These 222-nanometer radiation devices are deployed in bathrooms, classrooms, and meeting rooms without fully considering the potential benefits and/or hazards of their operation. This work lays the foundation for appropriately quantifying the potential negative impacts of these devices on health. Completing this process is crucial before relying on this technology to help prevent the next major outbreak.”