Ultraviolet Spectral Reflectance of Ceiling Tiles, and Implications for the Safe Use of Upper‐Room Ultraviolet Germicidal Irradiation

Wengraitis, Stephen; Reed, Nicholas G.

doi:10.1111/j.1751-1097.2012.01193.x

Cited by 11 publications

(13 citation statements)

References 13 publications

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“…Other potential applications of far-UVC light is sterilization of any environment with a high likelihood of airbornebased pathogen transmission, including tuberculosis, small pox, severe acute respiratory syndrome (SARS) and pandemic influenza, which collectively affects one billion people annually (47). Although upper-room UV-irradiation systems based on conventional broad-spectrum UV lamps (48) have long been considered for room sterilization (49)(50)(51), they cannot be widely used due to safety concerns relating to skin cancer and cataract risks (49,52,53).…”

Section: Discussionmentioning

confidence: 99%

Germicidal Efficacy and Mammalian Skin Safety of 222-nm UV Light

et al. 2017

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We have previously shown that 207-nm ultraviolet (UV) light has similar antimicrobial properties as typical germicidal UV light (254 nm), but without inducing mammalian skin damage. The biophysical rationale is based on the limited penetration distance of 207-nm light in biological samples (e.g. stratum corneum) compared with that of 254-nm light. Here we extended our previous studies to 222-nm light and tested the hypothesis that there exists a narrow wavelength window in the far-UVC region, from around 200–222 nm, which is significantly harmful to bacteria, but without damaging cells in tissues. We used a krypton-chlorine (Kr-Cl) excimer lamp that produces 222-nm UV light with a bandpass filter to remove the lower- and higher-wavelength components. Relative to respective controls, we measured: 1. in vitro killing of methicillin-resistant Staphylococcus aureus (MRSA) as a function of UV fluence; 2. yields of the main UV-associated premutagenic DNA lesions (cyclobutane pyrimidine dimers and 6-4 photoproducts) in a 3D human skin tissue model in vitro; 3. eight cellular and molecular skin damage endpoints in exposed hairless mice in vivo. Comparisons were made with results from a conventional 254-nm UV germicidal lamp used as positive control. We found that 222-nm light kills MRSA efficiently but, unlike conventional germicidal UV lamps (254 nm), it produces almost no premutagenic UV-associated DNA lesions in a 3D human skin model and it is not cytotoxic to exposed mammalian skin. As predicted by biophysical considerations and in agreement with our previous findings, far-UVC light in the range of 200–222 nm kills bacteria efficiently regardless of their drug-resistant proficiency, but without the skin damaging effects associated with conventional germicidal UV exposure.

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Section: Discussionmentioning

confidence: 99%

Germicidal Efficacy and Mammalian Skin Safety of 222-nm UV Light

et al. 2017

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“…In fact upper-room UV irradiation systems have long been considered, based on conventional broad-spectrum UV lamps [60], and have shown some promise [61], [62]; they have not, however, been widely used, in part because of safety concerns relating to potential low-level broad-spectrum UV exposure [61], [63], [64].…”

Section: Discussionmentioning

confidence: 99%

207-nm UV Light - A Promising Tool for Safe Low-Cost Reduction of Surgical Site Infections. I: In Vitro Studies

et al. 2013

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Background0.5% to 10% of clean surgeries result in surgical-site infections, and attempts to reduce this rate have had limited success. Germicidal UV lamps, with a broad wavelength spectrum from 200 to 400 nm are an effective bactericidal option against drug-resistant and drug-sensitive bacteria, but represent a health hazard to patient and staff. By contrast, because of its limited penetration, ∼200 nm far-UVC light is predicted to be effective in killing bacteria, but without the human health hazards to skin and eyes associated with conventional germicidal UV exposure.AimsThe aim of this work was to test the biophysically-based hypothesis that ∼200 nm UV light is significantly cytotoxic to bacteria, but minimally cytotoxic or mutagenic to human cells either isolated or within tissues.MethodsA Kr-Br excimer lamp was used, which produces 207-nm UV light, with a filter to remove higher-wavelength components. Comparisons were made with results from a conventional broad spectrum 254-nm UV germicidal lamp. First, cell inactivation vs. UV fluence data were generated for methicillin-resistant S. aureus (MRSA) bacteria and also for normal human fibroblasts. Second, yields of the main UV-associated pre-mutagenic DNA lesions (cyclobutane pyrimidine dimers and 6-4 photoproducts) were measured, for both UV radiations incident on 3-D human skin tissue.ResultsWe found that 207-nm UV light kills MRSA efficiently but, unlike conventional germicidal UV lamps, produces little cell killing in human cells. In a 3-D human skin model, 207-nm UV light produced almost no pre-mutagenic UV-associated DNA lesions, in contrast to significant yields induced by a conventional germicidal UV lamp.ConclusionsAs predicted based on biophysical considerations, 207-nm light kills bacteria efficiently but does not appear to be significantly cytotoxic or mutagenic to human cells. Used appropriately, 207-nm light may have the potential for safely and inexpensively reducing surgical-site infection rates, including those of drug-resistant origin.

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“…Previous studies proposed that the maximum reflectance for all upper‐room surfaces could be increased from 0.05 to 0.10 for higher fluence rate in the upper zone 40 . However, our results show that a detailed analysis of the duration of exposure is needed when the reflectance coefficients of the ceiling or walls are 0.1, to avoid harmful impact to the occupants.…”

Section: Resultsmentioning

confidence: 68%

“…In addition to the direct UV‐C radiation from the UVGI fixture, a portion of the UV‐C irradiance received at any point in the space was the result of interreflections between room surfaces. Recommendations by existing guidelines 16,39,40 on the allowable surface reflectance values for materials used in an occupied room are as follows: some recommend 0.05 maximum reflectance, and others 0.1 maximum reflectance for room materials where UVGI is used. In our model, we set 0.05 as the default reflectance coefficient for all room surfaces, to meet the stricter standard.…”

Section: Methodsmentioning

confidence: 99%

Spatial analysis of the impact of UVGI technology in occupied rooms using ray‐tracing simulation

2021

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The use of Ultraviolet Germicidal Irradiation (UVGI) devices in the upper zones of occupied buildings has gained increased attention as one of the most effective mitigation technologies for the transmission of COVID‐19. To ensure safe and effective use of upper‐room UVGI, it is necessary to devise a simulation technique that enables engineers, designers, and users to explore the impact of different design and operational parameters. We have developed a simulation technique for calculating UV‐C fluence rate within the volume of the upper zone and planar irradiance in the lower occupied zone. Our method is based on established ray‐tracing light simulation methods adapted to the UV‐C wavelength range. We have included a case study of a typical hospital patient room. In it, we explored the impact of several design parameters: ceiling height, device location, room configuration, proportions, and surface materials. We present a spatially mapped parametric study of the UV‐C irradiance distribution in three dimensions. We found that the ceiling height and mounting height of the UVGI fixtures combined can cause the largest variation (up to 22%) in upper zone fluence rate. One of the most important findings of this study is that it is crucial to consider interreflections in the room. This is because surface reflectance is the design parameter with the largest impact on the occupant exposure in the lower zone: Applying materials with high reflectance ratio in the upper portion of the room has the highest negative impact (over 700% variation) on increasing hot spots that may receive over 6 mJ/cm2 UV dose in the lower occupied zone.

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Ultraviolet Spectral Reflectance of Ceiling Tiles, and Implications for the Safe Use of Upper‐Room Ultraviolet Germicidal Irradiation

Cited by 11 publications

References 13 publications

Germicidal Efficacy and Mammalian Skin Safety of 222-nm UV Light

Germicidal Efficacy and Mammalian Skin Safety of 222-nm UV Light

207-nm UV Light - A Promising Tool for Safe Low-Cost Reduction of Surgical Site Infections. I: In Vitro Studies

Spatial analysis of the impact of UVGI technology in occupied rooms using ray‐tracing simulation

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