In this pilot study, immediate and delayed eye discomfort were assessed in a simulated office environment with deployment of 222 nm Far-UVC lamps, located on the ceiling and directed downwards into the occupied room. Discomfort was assessed immediately postexposure and several days after exposure using validated, Standard Patient Evaluation Eye Dryness (SPEED) and Ocular Surface Disease Index (OSDI) questionnaires.
Far-UVC in this simulated office environment did not cause any clinically significant eye discomfort and was effective at reducing pathogens in the room. These results contribute an important step to further investigation of the interaction of Far-UVC with the human eye.
In a hospital environment, 48 locations were tested for SARS-CoV-2 using RT-PCR (33.3% contamination rate). After series dosages of 222 nm Far-UVC exposure, samples from the surfaces were negative (100% eradication) after 15 seconds irradiation at 2 cm length (fluence: 81 mJ/cm2).
[Pending Peer Review]
This study uses computer simulations to effectively reproduce data from experiments in a room-sized chamber with aerosolized Staphylococcus aureus bacteria. Application of the validated model suggests that germicidal Far-UVC lamps could reduce levels of airborne human coronavirus by more than 90% in rooms with low ventilation rates. The inactivation of pathogens by Far-UVC is more efficient than previously thought, due to the complex path that particles take within the three dimensional airflow and UVC irradiance pattern.
Depending on the UVC-susceptibility of the aerosolized pathogen, Far-UVC lamps have the potential to provide effective room air change rates in excess of 100 equivalent air changes per hour, much greater than is possible with mechanical ventilation or filtration devices. The success of our simulations at reproducing the experimental data provides confidence that we can simulate larger environments and inform best practices for installations of germicidal Far-UVC lamps.
This study examined the penetration depth of ultraviolet (UV) light in the corneal limbus and assessed the safety of 222nm Far-UVC on stem cells in the basal area of the corneal limbus. Rats were exposed to various peaks of ultraviolet light.
Porcine cornea, which is similar to the human eye in size and structure, were irradiated with 222 far-UVC and 254 nm conventional UVC. As in rats, 222 nm Far-UVC reached only the superficial layer of the porcine corneal limbal epithelium. These results indicate that Far-UVC light could not reach corneal epithelial stem cells i.e. the cells remained intact.
This paper summarizes findings from various efficacy and safety studies; ultimately making conclusions based on those studies.
The evidence for far-UVC efficacy is strong, with clear evidence that far-UVC can produce Equivalent Air Change rates that are higher than for any other practical indoor air-cleaning approach. The paper by Ma et al. in the current issue provides good evidence that far-UVC will be effective against multiple common pathogens.
The evidence for far-UVC safety after prolonged far-UVC exposures is also strong, assuming that the (1) filtered far-UVC lamps are used, and (2) daily exposures are kept within current regulatory guidelines. The overarching reason to characterize the safety evidence as “strong” is that it comes from three different avenues: First, the basic biophysics of the penetration of far-UVC light into biological material; second, the extensive peer-reviewed published safety data when using filtered far-UVC light, and finally the recent decision of the ACGIH, based on the available experimental evidence, to significantly increase their recommended daily limits for far-UVC light.
Two filtered 222 nm Far-UVC lamps were installed in the examination room of an ophthalmology department (dose limit set to old ACGIH TLVs). The eyes and lids of the six ophthalmologists (5 wore glasses for myopic correction) who worked in the room for a mean stay of 6.7 h week-1 were prospectively observed for 12 months.
Slitlamp examinations revealed neither acute adverse events such as corneal erosion, conjunctival hyperemia, and lid skin erythema nor chronic adverse events such as pterygium, cataract, or lid tumor. The visual acuity, refractive error, and corneal endothelial cell density remained unchanged during the study.
This study used a ceiling-mounted far-UVC fixture emitting at 222 nm and then evaluated the doses received upon a manikin. Variables examined included manikin height (sitting or standing position), manikin offset from directly below the fixture, tilt of the manikin, the addition of glasses, the addition of hair, and different anatomical feature sizes.
Importantly, at the manikin position with the highest dose to eyes, the average eye dose was only 5.8% of the maximum directly measured dose. These results show that doses a human would experience from an indoor far-UVC installation are in fact much lower than the maximum directly measured dose.
This study assessed far-UVC induced carcinogenic skin changes and other abnormalities in hairless mice of both sexes that were exposed to high average daily doses of 222 nm far-UVC radiation for 66 weeks, 5 days per week, 8 hours per day, as well as similarly-treated unexposed controls.
No evidence for increased skin cancer, abnormal skin growths, or incidental skin pathology findings was observed in the far-UVC exposed mice. In addition, there were no significant changes in morbidity or mortality. The findings from this study support the long-term safety of long-term chronic exposure to far-UVC light, and therefore its potential suitability as a practical anti-microbial approach to reduce airborne viral and bacterial loads in occupied indoor settings.
This study evaluated the importance of using a bandpass filter to ensure 222 nm Far-UVC safety. Mice were irradiated with UVC emitted from a KrCl excimer lamp with or without a bandpass filter. UVC emitted from an unfiltered KrCl lamp at doses of 50, 150 and 300 mJ/cm2 induced cyclobutyl pyrimidine dimer (CPD)-positive cells, whereas UVC emitted from a filtered lamp did not significantly increase CPD-positive cells in the epidermis.
This study concludes that a much lower far-UVC dose is required than previously thought in order to inactivate the great majority of the airborne aerosolized pathogens in a room environment. The study used human coronavirus OC43 (HCoV-OC43) which is a suitable surrogate for SARS-CoV-2 with comparable physical and genomic size.
These new results offer further evidence as to the efficacy of far-UVC to inactivate airborne pathogens.
Filtered Far-UVC lamps showed reduction of steady-state aerosolized Staphylococcus aureus loads by 92.1%, providing an additional 35 equivalent air changes per hour (eACH). This makes the technology ideal for rooms and buildings lacking mechanical ventilation systems.
Efficacy and eACH results in this study were obtained with lamps operating within current ACGIH/IEC exposure limits. The efficacy and eACH are expected to be significantly higher when ACGIH/IEC adopts the proposed exposure limits (20-time higher than current limits).
This study evaluates exposure of 222 nm far-UVC on surgical fields not covered with skin in a rabbit model. Five types of tissue were surgically exposed with 222 nm far-UVC and conventional 254 nm UVC. DNA damage was significantly higher for conventional 254 nm UVC in all tissue types. 222 nm far-UVC showed no significant difference in four tissue types, with the exception of fat tissues whose DNA damage had reduced to control level after a mere 24 hours of exposure.
This data suggests that 222 nm Far-UVC irradiation could be a new method to safely prevent Surgical Site Infections (SSIs).
This study investigated the DNA damage caused by Far-UVC 222 nm on human skin reconstructs after additional optical filtering. The skin reconstructs were irradiated with 100 mJ/cm2, 500 mJ, and 3 × 500 mJ unfiltered and filtered (230–270 nm suppressed) far-UVC or UVB (308 nm) radiation.
UVB and non-filtered UVC irradiation induced a significant amount of CPDs, compared with the background. Filtered far-UVC lowered the CPD amount compared with unfiltered UVC and UVB treatments. Repetitive UVC irradiation did not result in the accumulation of CPDs compared with UVB treatment.
Reduction in excess of 99.9% of E. coli, S. aureus and C. albicans was detected after applying far-UVC radiation. This identifies a therapeutic window in which microorganisms are killed but tissue is still alive and not damaged, which could give rise to new clinical applications.
This study determined the efficiency of different UV wavelengths in killing pathogens, specifically SARS-CoV-2, to support efforts to control the ongoing COVID-19 global pandemic and future coronavirus-caused respiratory virus pandemics.
This study determined that human-safe 222nm Far-UVC light is not only safe, but also more effective at inactivating viruses like SARS-CoV-2 compared to harmful UV wavelengths. As such, it offers immense potential for applications in public spaces to effectively reduce viral aerosol and surface-based transmissions.
This study used Monte Carlo radiative transport (MCRT) to simulate light propagation through a multi-layered skin model for the wavelength range of 200–1000 nm. As anticipated, the study found that the penetration depth of light into skin varies with wavelength in accordance with the optical properties of skin.
The penetration depth of light into skin increases with wavelength from the UV to the visible light range before decreasing again in the IR range in accordance with the selected optical properties.
This study compared various UV technologies at two room ventilation rates (~1.4 ACH & ~6.8 ACH), as well as number of UV lamps and their exposure limits. It was determined that for new ACGIH TLVs, a single isotropic far-UVC lamp (with a diffused field of view, FoV) is more effective at reducing airborne microbial concentration than even Upper Room UV technologies (a popular technology in healthcare facilities for reducing airborne infection transmission).
Using computer modelling, this study compared skin damage from sunlight to that from Far-UVC sources. In a temperate climate, which is similar to many parts of North American and Europe, 10 minutes of daylight at a UV index of 4 which is typical from Spring to Fall, produced as much damage as 30,000 hours of filtered Far-UVC at the basal layer of the skin and 300 hours at the top of the epidermis.
Effectively, this research concludes that filtered Far-UVC light is about 180,000-times safer than sunlight at the basal layer of the skin under the researched parameters. At the top of the epidermis, filtered Far-UVC light is about 1,800-times safer than sunlight under the researched parameters.
This study performed human skin irradiation in two settings using a filtered 222 nm Far‐UVC source: 1) In a novel ex vivo full‐thickness human skin model cultured at tension (manuscript in preparation); and 2) Using in vivo self‐exposures. In vivo, two of the authors irradiated their inner forearms at a very high far‐UVC dose of 6,100 mJ/cm2 (265-times higher than existing ACGIH exposure limits), using the same irradiation source and distance as the ex vivo samples.
This study showed that even at very high exposure doses, appropriately filtered far‐UVC is unlikely to present a carcinogenic risk through direct DNA damage.
This pilot study in a shared bathroom concludes that 222nm Far-UVC is effective at disinfection in real world environments, and likely more effective that traditional cleaning methods which have "the problem of selecting inappropriate disinfectants; furthermore, some areas might remain uncleaned due to human errors. A previous study showed that only 50% of the surfaces in hospital rooms are sufficiently cleaned."
This study utilized identical lamps as UVX's.
Eye damage was evaluated in rates for significantly high doses of Far-UVC (between 10,000 and 15,000 mJ/cm2 at 207 nm and between 3,500 and 5,000 mJ/cm2 at 222 nm). The minimum dose to induce corneal damage of Far-UVC light was considerably higher than ACGIH TLVs. The property that explains why 207 nm and 222 nm Far-UVC is extremely less hazardous than longer UV wavelengths is the fact that this light only penetrates to the outermost layer of the corneal epithelium. These cells typically peel off within 24-hours during the physiological turnover cycle. Hence, Far-UVC light might be less hazardous to the cornea than previously considered until today.
This paper conducted a literature search on the impact of far-UVC radiation on pathogens, cells, skin and eyes was performed and median log-reduction doses for different pathogens and wavelengths were calculated. Observed damage to cells, skin and eyes was collected and presented in standardized form.
More than 100 papers on far-UVC disinfection, published within the last 100 years, were found. Far-UVC radiation, especially the 222 nm emission of KrCl excimer lamps, exhibits strong antimicrobial properties. The average necessary log-reduction doses are 1.3 times higher than with 254 nm irradiation. A dose of 100 mJ/cm2 reduces all pathogens by several orders of magnitude without harming human cells, if optical filters block emissions above 230 nm.
This paper reviews strong scientific data to-date that shows 222 nm Far-UVC is safe, and that existing ACGIH Threshold Limit Value (TLVs) of 23 mJ/cm2 over 8-hours are overly conservative. The paper also proposes adjustments to ACGIH exposure limits for UVC wavelengths below 250 nm (including 222 nm Far-UVC).
Current management of pressure wounds is limited to mainly conservative measures, such as offloading therapies and regular wound care. Reduction of bacterial load remains an important step in wound bed preparation to encourage wound healing in such wounds.
This research is the first human clinical trial using 222nm Far-UVC in eradicating bacteria in human wounds. The study concludes that filtered 222nm Far-UVC light is effective and safe at reducing bacterial loads on pressure ulcers (PUs) in human patients. No adverse events were reported in any of the patients.
A 37-year-old male, Fitzpatrick Skin Type II, performed multiple self-exposures with a filtered 222 nm Far-UVC lamp. No erythema was observed at any time point with exposures up to 18000 mJ/cm (about 783-timeshigher than maximum exposure limits).
These results combined with Monte Carlo Radiative Transfer computer modeling suggest that filtering longer ultraviolet wavelengths is critical for the human skin safety of far-UVC devices. This work also contributes to growing arguments for the exploration of exposure limit expansion, which would subsequently enable faster inactivation of viruses.
This research compares filtered and unfiltered 222nm Far-UVC lamp safety on skin. The study further emphasizes the importance of using optical filters with 222nm Far-UVC lamps in ensuring safety, concluding that unfiltered Far-UVC lamps result in statistically significant increase in the yield of DNA damage whereas filtered Far-UVC lamps do not induce the same.
The model shows that disinfection rates are increased by an "additional" 50-85% when using 222nm Far-UVC within currently recommended exposure levels compared to the room’s ventilation alone. In all scenarios explored within this research, Far-UVC can reduce in-room SARS-CoV-2 concentrations to levels comparable to that provided practically by breathing through an N95 mask
With these magnitudes of reduction, 222nm Far-UVC light could be employed to mitigate SARS-CoV-2 transmission before the onset of future waves, or the start of winter when risks of infection are higher. This is particularly significant in poorly-ventilated spaces where other means of reduction are not practical, in addition social distancing can be reduced without increasing the risk.
A dosage as small as 3 mJ/cm2 of 222nm Far-UVC light resulted in 99.7% reduction of SARS-CoV-2, the pathogen that causes COVID-19. These results suggest that this technology could be used for infection prevention and control against COVID-19 and other infectious diseases, not only in unoccupied spaces but also occupied spaces.
This study aimed to investigate the safety of 222nm Far-UVC light and to examine its skin sterilization effect in healthy volunteers.
All subjects experienced no skin erythema at all doses. The back of the subject was irradiated at 500 mJ/cm2, and the number of bacterial colonies in the skin swab culture was significantly decreased by 222nm Far-UVC exposure.
A 222nm Far-UVC dosage at 500 mJ/cm2, which is about 22.7-times higher than UVX’s maximum programmed dosage, was a safe irradiation dose while possessing germicidal effects.
This research provides further evidence that filtered 222nmFar-UVC light has no immediate or delayed harmful effects on mice skin andeyes.
Long-term effects of 222nm Far-UVC were investigated on a type of mice species that lacks the genetic ability to repair the most prominent type of DNA damage from conventional non-Far-UVC light.
Despite the mice being significantly more susceptible to UV light by being unable to repair DNA damage, 222nm Far-UVC proved to be non-carcinogenic and safe for both skin and eyes long-term.
222nm Far-UVC is effective at decontaminating airborne human coronaviruses alpha HCoV-229E and beta HCoV-OC43.
Continuous airborne disinfection with 222nm Far-UVC light at the current regulatory limits that UVX follows would provide a major reduction in the ambient level of airborne virus in occupied indoor environments.
This study by Barnard et al emphasizes the importance of using an optical filter to ensure 222nm Far-UVC safety, proving that filtered 222nm Far-UVC is safe but unfiltered 222nm Far-UVC is not.
In 2014, Woods et al undertook a first‐in‐person study to assess the effect on skin of a 222nm Far-UVC emitting device (a disinfection wand). The study concluded that damage was induced on human skin. Woods et al hypothesized that a small amount of longer wavelength UVC light above 250 nm (<3%) may be contributing to the observed effects. These wavelengths were emitted as the 222nm Far-UVC emitting device did not utilize an optical filter to eliminate wavelengths outside the 200nm to 230nm range (the safe wavelengths), with wavelengths below 200nm and above 230nm being unsafe.
This study by Bernard et al concluded that skin damage documented by Woods et al arose from very low intensity source emissions above 230nm due to the lack of an optical filter (as low as 3% above 250nm). With the proper use of an optical filter to eliminate harmful UV wavelengths, this study confirmed that filtered 222nm Far-UVC light is safe for humans and does not induce skin damage.
A Eadie et al case study also confirmed the criticality of an optical filter to ensure 222nm-Far-UVC safety by tests on human skin.
222nm Far-UVC had a potent germicidal effect on vegetative bacterial cells, yeast and viruses, and was as efficient as 245nm UVC. In addition, 222nm Far-UVC had a more potent germicidal effect on bacterial endospores compared with 254nm UVC.
However, the fungicidal effect of 222nm Far-UVC against fungal spores and hyphae was weaker than that of 254nm UVC. UVX’s 222nm Far-UVC technology is not intended for fungal spores disinfection.
No corneal damage was induced by 222nm Far-UVC light, which suggested that 222nm Far-UVC light does not harm rat eyes within the tested dosage ranges. These dosages are significantly higher than UVX’s maximum programmed dosage.
Mice were subjected to daily 222nm Far-UVC dosage of 450 mJ/cm2 per day for a total of 10 days. Despite this dosage being 7-times higher than UVX’s maximum programmed dosage, it did not induce a mutagenic or cytotoxic effect on mice skin.
In the circumstance of superficial incisions infected with bacteria alighting onto the wound, 222nm Far-UVC light showed the same germicidal properties of 254nm UVC light but without the associated skin damage.
Being safe for patient and hospital staff, our results suggested that far-UVC light (222 nm) might be a convenient approach to prevent transmission of drug-resistant infectious agents in the clinical setting.
222nm Far-UVC is effective at decontaminating aerosolized influenza A virus (H1NA) with doses as low as 2 mJ/cm2.
Surgical site infection is the most common type of infection occurring in hospitals, caused by contamination of surgical wounds with natural commensal bacteria and by hospital pathogens, of which methicillin-resistant Staphylococcus aureus (MRSA) is one of the most frequently detected.
222nm Far-UVC is effective at decontaminating MRSA.
222nm Far-UVC is effective at killing MRSA bacteria, produces no DNA lesions in a 3D human skin model, and does not cause cell damage in mammalian skin.
Mice were continuously exposed to a 222nm Far-UVC dosage of 157 mJ/cm2 per 7 hours, more than 8-times UVX's maximum programmed dosage, and still showed no skin damage.
This is Phase 2 of a similar study. Phase 1 of the study was conducted in-vitro whereas Phase 2 was conducted in-vivo.
This study exposed hairless mice to a dosage of 157mJ/cm2 using a filtered Krypton-Bromine Far-UVC lamp with a peak wavelength of 207nm. The same mice species were also exposed to conventional 254nm UVC light.
While conventional 254nm UVC exposure produced significant damage to the mice skin, the same dosage of 207nm Far-UVC light produced results that were not statistically distinguishable from the zero UV exposure controls.
207nm light is within the Far-UVC range (200nm to 230nm).The study concluded that filtered Far-UVC light kills bacteria efficiently but does not appear to be significantly cytotoxic or mutagenic to human cells.