Wikipedia

Draft:Far-UVC

{{Connected contributor|User1=RDX300|U1-declared=yes| I work for a pandemic preparedness nonprofit called Blueprint Biosecurity that researches pandemic preparedness interventions like far-UVC. We have no commercial affiliations towards or vested interest in promoting far-UVC. We are a nonpartisan research organization.}}
National Guard soldiers standing in circle gesture at small white device mounted to ceiling in office-like military facility.
A Far-UVC Krypton Chloride excimer lamp is used to disinfect the air in a National Guard facility.

Far-UVC describes a type of ultraviolet germicidal irradiation being studied[1] and commercially developed[2] for its combination of pathogen inactivation properties and reduced negative effects on human health[3][4] when used within exposure guidelines.

Far-UVC (200-235 nm), while part of the broader UV-C spectrum (100-280 nm), is distinguished by its unique biophysical effects on living tissues. Unlike conventional UV-C lamps (which typically have peak emissions at 254 nm), far-UVC demonstrates significantly reduced penetration into biological tissue. This limited penetration depth is primarily due to strong absorption by proteins at wavelengths below 240 nm[5]. Consequently, far-UVC photons are mostly absorbed in the outer protective layers of skin[6] and eyes[7] before reaching sensitive cells, resulting in minimal health effects. However, far-UVC can still lead to negative health effects through reactive byproducts like ozone.

While the technology has been studied since the early 2010s, heightened demand for disinfectant tools during the COVID-19 pandemic played a significant role in spurring both academic and commercial interest into far-UVC. Unlike conventional germicidal UV-C lamps, which are limited to upper-room pathogen inactivation or use in unoccupied spaces due to their negative effects on human skin and eyes, far-UVC is considered promising for whole-room pathogen inactivation due to its enhanced safety. This allows for the installation of far-UVC lights on ceilings, potentially enabling direct disinfection of the breathing zone while people are present.

Although far-UVC shows potential for implementation in a wide variety of use cases, its wider adoption as a pandemic prevention strategy requires further research around its safety and efficacy.

Historical Development

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Far-UVC's development was primarily led by the research of Dr. David J. Brenner and his colleagues (including David Welch and Manuela Buonanno) at Columbia University's Center for Radiological Research. In the early 2010s, Brenner initially studied far-UVC for its potential as a surgical site disinfectant[8]. Over the next decade, his lab began to study the technology for its ability to prevent the airborne transmission of pathogens, as well as its health effects on mammalian skin[9]. In 2018, a seminal paper published by Brenner's lab announced the technology as an inexpensive and safe technology to reduce the spread of airborne microbial diseases like tuberculosis and influenza[3].

During the COVID-19 pandemic far-UVC research[10] and commercialization[2] efforts increased. The technology is currently being further studied for its safety and efficacy, particularly regarding its effect on ozone creation[11] and interactions with indoor air chemistry and the built environment[12]. Latest studies uphold initial evidence towards the technology's germicidal efficacy in realistic room-like environments[1].

Safety and Efficacy

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Research from the Brenner lab and other scientists has demonstrated the improved safety and efficacy profile of far-UVC compared to other ultraviolet wavelengths[13]. When evaluating ultraviolet germicidal lights, eye and skin health are primary concerns. UV-B, predominantly responsible for the harmful effects of sunlight, poses the highest risk for erythema, photokeratitis, sunburn and skin cancer[14][15][16]. While longer UV-C wavelengths and UV-A can also cause damage, their effects are less severe than UV-B.

In contrast, far-UVC has shown remarkably different results. Studies on both lab mice[17][18] and humans[19] have found no significant impact on skin health, even at doses far exceeding current guidelines[20]. This enhanced safety is attributed to far-UVC's difficulty in penetrating the outermost layer of the epidermis called the stratum corneum[5]. The stratum corneum is effective at blocking far-UVC as it's composed primarily of dead cells filled with keratin protein, which absorb far-UVC light.

Regarding ocular safety, while comprehensive human studies are still pending, limited research has been conducted on human eye exposure to overhead far-UVC lamps. These studies have found no evidence of damage or increased discomfort[21][22]. Additionally, research on rats has revealed significantly reduced penetration and damage from far-UVC compared to other UV wavelengths[23][24][25]. These findings suggest a promising safety profile for far-UVC, though further research, particularly on human eyes, is needed to fully establish its long-term effects.

When far-UVC interacts with with airborne oxygen it produces ozone and other byproducts[26][27][28][29], an effect that has been demonstrated in laboratory and real world environments[30][31][32]. While the extent to which this produced ozone leads to negative health effects is the subject of active research[33][34][35], the mechanism for ozone causing cardiovascular disease and premature morality is established in outdoor settings[36].

A key concern for far-UVC implementations is balancing radiation dosage and microbial inactivation rates[37]. Although far-UVC has been shown to be effective at inactivating a wide array at viruses at doses that fall beneath exposure limits[38][39], the optimal dosage for achieving sufficient deactivation and indoor air quality standards[40] requires further study.

Positive skin and eye safety attributes can be forgone if a given far-UVC lamp produces unwanted emissions at wavelengths other than the a device's stated specifications. For this reason, optical filters have been suggested as a mitigation device[41]. Mitigation techniques also have been studied for ozone production[42].

Far-UVC Devices and Commercialization

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The most common device used to generate far-UVC radiation is a Krypton Chloride (KrCl) excimer lamp, which emits light at the 222 nm wavelength. Following the sudden increase in demand for disinfectant tools brought upon by the COVID-19 pandemic, a number of companies began to market and sell consumer far-UVC devices. These devices comes in many different configurations and commercial form factors. There are no public estimates available for the size of the far-UVC device industry.

Regulation

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Considering the technology's evolving nature, regulatory bodies around the world have not yet created binding standards as to what is considered a safe and effective dosage for far-UVC implementations, nor have they created certifications or passed regulations for the safety of commercial far-UVC devices. Legislation has been proposed for governing the production of ozone from germicidal UV light in California[43]. In lieu of formal regulations or standards, guidelines for exposure limits and indoor air quality are put in place by professional associations[13][44][45]. Some have suggested that these exposure limits are too conservative and need to be revised for shorter wavelength UV-C[46].

References

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  1. ^ a b "Far-UVC Light Can Virtually Eliminate Airborne Virus in an Occupied Room". Columbia University Irving Medical Center. 2024-04-02. Retrieved 2024-07-21.
  2. ^ a b Morrissey, Janet (2020-06-16). "Fighting the Coronavirus With Innovative Tech". The New York Times. ISSN 0362-4331. Retrieved 2024-07-21.
  3. ^ a b Welch, David; Buonanno, Manuela; Grilj, Veljko; Shuryak, Igor; Crickmore, Connor; Bigelow, Alan W.; Randers-Pehrson, Gerhard; Johnson, Gary W.; Brenner, David J. (2018-02-09). "Far-UVC light: A new tool to control the spread of airborne-mediated microbial diseases". Scientific Reports. 8 (1): 2752. Bibcode:2018NatSR...8.2752W. doi:10.1038/s41598-018-21058-w. ISSN 2045-2322. PMC 5807439. PMID 29426899.
  4. ^ Blatchley, Ernest R.; Brenner, David J.; Claus, Holger; Cowan, Troy E.; Linden, Karl G.; Liu, Yijing; Mao, Ted; Park, Sung-Jin; Piper, Patrick J.; Simons, Richard M.; Sliney, David H. (2023-03-19). "Far UV-C radiation: An emerging tool for pandemic control". Critical Reviews in Environmental Science and Technology. 53 (6): 733–753. Bibcode:2023CREST..53..733B. doi:10.1080/10643389.2022.2084315. ISSN 1064-3389.
  5. ^ a b Görlitz, Maximilian; Justen, Lennart; Rochette, Patrick J.; Buonanno, Manuela; Welch, David; Kleiman, Norman J.; Eadie, Ewan; Kaidzu, Sachiko; Bradshaw, William J.; Javorsky, Emilia; Cridland, Nigel; Galor, Anat; Guttmann, Martin; Meinke, Martina C.; Schleusener, Johannes (May 2024). "Assessing the safety of new germicidal far-UVC technologies". Photochemistry and Photobiology. 100 (3): 501–520. doi:10.1111/php.13866. ISSN 0031-8655. PMID 37929787.
  6. ^ Fukui, Tomoaki; Niikura, Takahiro; Oda, Takahiro; Kumabe, Yohei; Ohashi, Hiroyuki; Sasaki, Masahiro; Igarashi, Tatsushi; Kunisada, Makoto; Yamano, Nozomi; Oe, Keisuke; Matsumoto, Tomoyuki; Matsushita, Takehiko; Hayashi, Shinya; Nishigori, Chikako; Kuroda, Ryosuke (2020-08-12). "Exploratory clinical trial on the safety and bactericidal effect of 222-nm ultraviolet C irradiation in healthy humans". PLOS ONE. 15 (8): e0235948. Bibcode:2020PLoSO..1535948F. doi:10.1371/journal.pone.0235948. ISSN 1932-6203. PMC 7423062. PMID 32785216.
  7. ^ Kaidzu, Sachiko; Sugihara, Kazunobu; Sasaki, Masahiro; Nishiaki, Aiko; Igarashi, Tatsushi; Tanito, Masaki (2019-06-03). "Evaluation of acute corneal damage induced by 222-nm and 254-nm ultraviolet light in Sprague–Dawley rats". Free Radical Research. 53 (6): 611–617. doi:10.1080/10715762.2019.1603378. ISSN 1071-5762. PMID 30947566.
  8. ^ Buonanno, Manuela; Randers-Pehrson, Gerhard; Bigelow, Alan W.; Trivedi, Sheetal; Lowy, Franklin D.; Spotnitz, Henry M.; Hammer, Scott M.; Brenner, David J. (2013-10-16). "207-nm UV Light - A Promising Tool for Safe Low-Cost Reduction of Surgical Site Infections. I: In Vitro Studies". PLOS ONE. 8 (10): e76968. Bibcode:2013PLoSO...876968B. doi:10.1371/journal.pone.0076968. ISSN 1932-6203. PMC 3797730. PMID 24146947.
  9. ^ Buonanno, Manuela; Ponnaiya, Brian; Welch, David; Stanislauskas, Milda; Randers-Pehrson, Gerhard; Smilenov, Lubomir; Lowy, Franklin D.; Owens, David M.; Brenner, David J. (April 2017). "Germicidal Efficacy and Mammalian Skin Safety of 222-nm UV Light". Radiation Research. 187 (4): 483–491. Bibcode:2017RadR..187..493B. doi:10.1667/RR0010CC.1. ISSN 0033-7587. PMC 5552051. PMID 28225654.
  10. ^ Welch, David; Buonanno, Manuela; Buchan, Andrew G.; Yang, Liang; Atkinson, Kirk D.; Shuryak, Igor; Brenner, David J. (April 2022). "Inactivation Rates for Airborne Human Coronavirus by Low Doses of 222 nm Far-UVC Radiation". Viruses. 14 (4): 684. doi:10.3390/v14040684. ISSN 1999-4915. PMC 9030991. PMID 35458414.
  11. ^ Peng, Zhe; Day, Douglas A.; Symonds, Guy A.; Jenks, Olivia J.; Stark, Harald; Handschy, Anne V.; de Gouw, Joost A.; Jimenez, Jose L. (2023-08-08). "Significant Production of Ozone from Germicidal UV Lights at 222 nm". Environmental Science & Technology Letters. 10 (8): 668–674. Bibcode:2023EnSTL..10..668P. doi:10.1021/acs.estlett.3c00314. ISSN 2328-8930.
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  13. ^ a b Görlitz, Maximilian; Justen, Lennart; Rochette, Patrick J.; Buonanno, Manuela; Welch, David; Kleiman, Norman J.; Eadie, Ewan; Kaidzu, Sachiko; Bradshaw, William J.; Javorsky, Emilia; Cridland, Nigel; Galor, Anat; Guttmann, Martin; Meinke, Martina C.; Schleusener, Johannes (May 2024). "Assessing the safety of new germicidal far-UVC technologies". Photochemistry and Photobiology. 100 (3): 501–520. doi:10.1111/php.13866. ISSN 0031-8655. PMID 37929787.
  14. ^ Ikehata, Hironobu; Mori, Toshio; Kamei, Yasuhiro; Douki, Thierry; Cadet, Jean; Yamamoto, Masayuki (January 2020). "Wavelength- and Tissue-dependent Variations in the Mutagenicity of Cyclobutane Pyrimidine Dimers in Mouse Skin". Photochemistry and Photobiology. 96 (1): 94–104. doi:10.1111/php.13159. ISSN 0031-8655. PMID 31461538.
  15. ^ Rochette, P. J. (2003-06-01). "UVA-induced cyclobutane pyrimidine dimers form predominantly at thymine-thymine dipyrimidines and correlate with the mutation spectrum in rodent cells". Nucleic Acids Research. 31 (11): 2786–2794. doi:10.1093/nar/gkg402. PMC 156735. PMID 12771205.
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  17. ^ Cadet, Jean (July 2020). "Harmless Effects of Sterilizing 222-nm far-UV Radiation on Mouse Skin and Eye Tissues". Photochemistry and Photobiology. 96 (4): 949–950. doi:10.1111/php.13294. ISSN 1751-1097. PMID 32526045.
  18. ^ Welch, David; Kleiman, Norman J.; Arden, Peter C.; Kuryla, Christine L.; Buonanno, Manuela; Ponnaiya, Brian; Wu, Xuefeng; Brenner, David J. (January 2023). "No Evidence of Induced Skin Cancer or Other Skin Abnormalities after Long-Term (66 week) Chronic Exposure to 222-nm Far-UVC Radiation". Photochemistry and Photobiology. 99 (1): 168–175. doi:10.1111/php.13656. ISSN 0031-8655. PMC 9691791. PMID 35614842.
  19. ^ Fukui, Tomoaki; Niikura, Takahiro; Oda, Takahiro; Kumabe, Yohei; Ohashi, Hiroyuki; Sasaki, Masahiro; Igarashi, Tatsushi; Kunisada, Makoto; Yamano, Nozomi; Oe, Keisuke; Matsumoto, Tomoyuki; Matsushita, Takehiko; Hayashi, Shinya; Nishigori, Chikako; Kuroda, Ryosuke (2020-08-12). "Exploratory clinical trial on the safety and bactericidal effect of 222-nm ultraviolet C irradiation in healthy humans". PLOS ONE. 15 (8): e0235948. Bibcode:2020PLoSO..1535948F. doi:10.1371/journal.pone.0235948. ISSN 1932-6203. PMC 7423062. PMID 32785216.
  20. ^ Eadie, Ewan; Barnard, Isla M. R.; Ibbotson, Sally H.; Wood, Kenneth (May 2021). "Extreme Exposure to Filtered Far-UVC: A Case Study †". Photochemistry and Photobiology. 97 (3): 527–531. doi:10.1111/php.13385. ISSN 0031-8655. PMC 8638665. PMID 33471372.
  21. ^ Sugihara, Kazunobu; Kaidzu, Sachiko; Sasaki, Masahiro; Ichioka, Sho; Takayanagi, Yuji; Shimizu, Hiroshi; Sano, Ichiya; Hara, Katsunori; Tanito, Masaki (May 2023). "One-year Ocular Safety Observation of Workers and Estimations of Microorganism Inactivation Efficacy in the Room Irradiated with 222-nm Far Ultraviolet-C Lamps". Photochemistry and Photobiology. 99 (3): 967–974. doi:10.1111/php.13710. ISSN 0031-8655. PMID 36081379.
  22. ^ Kousha, Obaid; O'Mahoney, Paul; Hammond, Robert; Wood, Kenneth; Eadie, Ewan (January 2024). "222 nm F ar- UVC from filtered K rypton- C hloride excimer lamps does not cause eye irritation when deployed in a simulated office environment". Photochemistry and Photobiology. 100 (1): 137–145. doi:10.1111/php.13805. ISSN 0031-8655. PMC 10952573. PMID 37029739.
  23. ^ Kaidzu, Sachiko; Sugihara, Kazunobu; Sasaki, Masahiro; Nishiaki, Aiko; Igarashi, Tatsushi; Tanito, Masaki (2019-06-03). "Evaluation of acute corneal damage induced by 222-nm and 254-nm ultraviolet light in Sprague–Dawley rats". Free Radical Research. 53 (6): 611–617. doi:10.1080/10715762.2019.1603378. ISSN 1071-5762. PMID 30947566.
  24. ^ Kaidzu, Sachiko; Sugihara, Kazunobu; Sasaki, Masahiro; Nishiaki, Aiko; Ohashi, Hiroyuki; Igarashi, Tatsushi; Tanito, Masaki (May 2021). "Re-Evaluation of Rat Corneal Damage by Short-Wavelength UV Revealed Extremely Less Hazardous Property of Far-UV-C †". Photochemistry and Photobiology. 97 (3): 505–516. doi:10.1111/php.13419. ISSN 0031-8655. PMC 8251618. PMID 33749837.
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  26. ^ Link, Michael F.; Shore, Andrew; Hamadani, Behrang H.; Poppendieck, Dustin (2023-08-08). "Ozone Generation from a Germicidal Ultraviolet Lamp with Peak Emission at 222 nm". Environmental Science & Technology Letters. 10 (8): 675–679. Bibcode:2023EnSTL..10..675L. doi:10.1021/acs.estlett.3c00318. ISSN 2328-8930. PMC 10938353. PMID 38487621.
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