Unwanted Indoor Air Quality Effects from Using Ultraviolet C Lamps for Disinfection

Abstract

Ultraviolet germicidal irradiation (UVGI) is known to inactivate various viruses and bacteria, including SARS-CoV-2, and is widely applied especially in medical facilities. This inactivation results from the high photon energies causing molecular bonds to break, but when nonpathogen molecules are affected, unwanted effects may occur. Here, we explored the effect of a commercial high-intensity (∼2 kW) UVC disinfection device on the composition and concentration of gases and particles in indoor air. We find that the UVC (254 nm) caused dramatic increases in particle number concentrations, and nearly all (∼1000) monitored gas phase species also increased. These responses were unsurprising when considering the typical impacts of UVC on atmospheric chemistry. High particle concentrations are associated with adverse health effects, suggesting that the impact of UVGI devices on indoor air quality (IAQ) should be studied in much more detail. The high-intensity device in this study was intended for short durations in unoccupied rooms, but lower-intensity devices for continuous use in occupied rooms are also widely applied. This makes further studies even more urgent, as the potential IAQ effects of these approaches remain largely unexplored.

Ozone Generation from a Germicidal Ultraviolet Lamp with Peak Emission at 222 nm

“…We note that the effective fluence rate (i.e., the average amount of light irradiating a given volume; Table S2) will depend on the GUV222 path length, and so the O 3 generation values reported here are most applicable to indoor spaces with volumes equal to, or larger than, 31.5 m 3 . Like the losses of O 3 to chamber walls and gas-phase reactions we observed, much higher reactive losses of O 3 generated from GUV222 devices would be expected in real indoor environments (e.g., k loss = 2 h –1 (surfaces) and k loss = 0.09 h –1 per person (human envelope)) with potential impacts for byproduct formation that would affect indoor air quality . Additionally, we note that the radiation dosing necessary to achieve high levels of virus deactivation may require multiple GUV222 lamps and thus our measured O 3 generation rate could be used to simulate the effects of multiple lamp installations on indoor air quality.…”

“…Like the losses of O 3 to chamber walls and gas-phase reactions we observed, much higher reactive losses of O 3 generated from GUV222 devices would be expected in real indoor environments (e.g., k loss = 2 h −1 (surfaces) and k loss = 0.09 h −1 per person (human envelope)) 26 with potential impacts for byproduct formation that would affect indoor air quality. 27 Additionally, we note that the radiation dosing necessary to achieve high levels of virus deactivation may require multiple GUV222 lamps 28 and thus our measured O 3 generation rate could be used to simulate the effects of multiple lamp installations on indoor air quality. We suggest that more measurements of O 3 production should be made from commercial air cleaning devices that use GUV222 lamps to assess the impacts on indoor air quality in both real indoor and laboratory settings.…”

Oxygen Effect on the Ultraviolet-C Photochemistry of Lactic Acid

“…As discussed previously, UVC has been used as a sterilization method in hospitals due to its germicidal effects and ability to deactivate some viruses. − Moreover, with the recent Coronavirus Disease 2019 (COVID-19) pandemic, UVC disinfection systems have seen a spike in sales, necessitating further studies for the safe usage of UVC radiation. Many of the safety studies performed to date have focused on the impact of direct radiation on DNA. ,, However, recent studies − and the work presented here shows that safety studies should also consider secondary reactions caused by UVC irradiation of organic molecules, including those resulting from human emissions in indoor environments.…”

“…). − ,, As mentioned previously, lactic acid is prevalent in indoor environments due to human emissions, where it will likely be found on surfaces or in aerosols due to its low vapor pressure. , We therefore suggest that lactic acid photolysis may be occurring in such indoor environments and could produce harmful byproducts during these UVC sterilization procedures. However, most photochemical studies address photochemistry in the modern Earth’s outdoor environment where UVC is not available, and thus, few studies have addressed photochemistry using radiation with energies equal to UVC sterilization procedures. − Previous work by Deal et al and others ,, suggests that lactic acid may be photoactive under these conditions and, if so, will produce harmful byproducts (e.g., CO and formic acid) that may remain even after the UVC sterilization is complete, thereby posing an indirect risk to human health. It is therefore important to understand the products and mechanisms of lactic acid photolysis in environments which more accurately model indoor environments (i.e., in the presence of oxygen).…”

The World Is Completely Unprepared For Detecting Emerging Viruses/Bacteria In The Air

“…GUV has been in use in many applications across DoD [73], in hospitals for infection control and to some extent for short-term or temporary exposure in public spaces. At this time a debate remains unresolved about long-term safety and appropriateness for extended, daily use of GUV [58] especially in regards to excessive generation of volatile organic compounds (VOC) and formation of secondary aerosols [59] [60] which may be carcinogenic [61].…”