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1.
Photochem Photobiol ; 2022.
Article in English | PubMed | ID: covidwho-2038178

ABSTRACT

Germicidal ultraviolet (UV) devices have been widely used for pathogen disinfection in water, air, and on food and surfaces. Emerging UV technologies, like the krypton chloride (KrCl*) excimer emitting at 222 nm, are rapidly gaining popularity due to their minimal adverse health effects compared to conventional UV lamps emitting at 254 nm, opening opportunities for UV disinfection in occupied public spaces. In this study, inactivation of seven bacteria and five viruses, including waterborne, foodborne, and respiratory pathogens, was determined in a thin-film aqueous solution using a filtered KrCl* excimer emitting primarily at 222 nm. Our results show that the KrCl* excimer can effectively inactivate all tested bacteria and viruses, with most microorganisms achieving more than 4-log (99.99%) reduction with a UV dose of 10 mJ/cm(2) . Compared to conventional UV lamps, KrCl* excimer exhibited better disinfection performance for viruses but was less effective for bacteria. The relationships between UV sensitivities at 222 nm and 254 nm for bacteria and viruses were evaluated using regression analysis, resulting in factors that could be used to estimate the KrCl* excimer disinfection performance from well-documented UV kinetics using conventional 254 nm UV lamps. This study provides fundamental information for pathogen disinfection when employing KrCl* excimers.

2.
Chinese Journal of Lasers-Zhongguo Jiguang ; 49(15), 2022.
Article in English | Web of Science | ID: covidwho-2006271

ABSTRACT

Objective The ongoing coronavirus pandemic has propelled the need for new approaches to disinfection, especially for airborne viruses. The 254 nm emission of low-pressure vacuum lamps is known for its antimicrobial effect;however, its radiation is harmful to human health, causing skin cancer and cataracts. Some studies have shown that short-wavelength ultraviolet (UV) light in the spectral region of 200-230 nm (far-UVC) can inactivate pathogens without harming human cells. Thus, it has great prospects for many applications. Sufficient studies have proved the antibacterial performance of far-UVC band range in an excimer lamp emitting a peak wavelength of 222 nm light. Furthermore, laser light sources can realize long-distance transmission and complement the deficiency of excimer lamps in remote sterilization and disinfection. This study investigates the antibacterial effect of a self-developed far-UVC laser with a peak wavelength of 228 nm and hopes to provide a new technical approach for the inactivation of the novel coronavirus and other microbial pathogens. Methods Bacterial sample preparation: Escherichia coli (E. coli) widely exists naturally and is a pathogen of major focus in human public health defense. It is also one of the most drug-resistant species in the enterobacterium group. Therefore, it is often used in ultraviolet disinfection and environmental health research. Bacillus cereus (B. cereus), which is closely related to humans, causes food poisoning and cannot be eliminated by pasteurization or normal hygiene procedures due to the heat and acid resistance of its spores. Therefore, the strains used in this experiment are E. coli and B. cereus. E. coli and B. cereus are provided by the Ministry of Education Key Laboratory for Ecology of Tropical Islands, Hainan Normal University, and subsp. Kustaki HD-1, provided by the Environmental Microbial Ecology Laboratory of Hainan Normal University. Both strains are cultured in a nutrient agar medium and placed in an incubator at 35 degrees C for 1 day. Nutrient agar medium is provided by Guangdong Huankai Microbial Technology Co., LTD, China. UV irradiation source: the irradiation source is a self-developed all-solid-state 228 nm far-UVC laser, which provides UV irradiance of up to 35 mW/cm(2), and its spectral linewidth is less than 0.1 nm. The laser is realized by LD-pumped Nd3+ laser crystal, Q-switched technology, and nonlinear optical frequency conversion technology. All-solid-state lasers have the advantages of small size, high efficiency, good beam quality, high reliability, long life, and portability. 228 nm far-UVC laser sterilization: we input a certain concentration of 1 mL bacterial suspension sample into a high permeability UVC cuvette. The 228 nm laser irradiance of 0.1 mW/cm(2) is obtained by adjusting the laser output power and the placement of the colorimeter. E. coli suspension samples are irradiated for 5, 10, 15, and 20 s [Fig. 1 (b), and B. cereus suspension samples are irradiated for 15, 30, 45, and 60 s [Fig. 1(c)] at 228 nm far-UV light of 0.1 mW/cm(2). The experiment is repeated three times for each sample at the same irradiation dose. Results and Discussions Figs. 1 (b) and (c) show the distribution of bacteria before and after 228 nm laser irradiation. The concentration of bacterial suspension samples in the control and irradiated groups is determined using the nutrient agar plate counting method. The detection results are shown in Table 1. When the E. coli suspension is irradiated by 228 nm laser for 10, 15, and 20 s (1, 1.5, and 2 mJ/cm(2)), the inactivation rates are 90. 7 %, 96.9 %, and 100 yo, respectively. When the B. cereus suspension is irradiated by 228 nm laser for 30, 45, and 60 s (3, 4. 5, and 6 mJ/cm(2)), the inactivation rates are 88. 4%, 98.6 %, and 100 %, respectively. Conclusions This experimental study shows that the use of several mJ/cm(2) doses of far-UVC 228 nm pulsed laser irradiation can effectively inactivate E. coli and B. cereus, whereas the use of excimer lamps requires dozens of mJ/cm(2) doses. Compared with the excimer light source, the far-UVC pulsed laser light source shows a stronger sterilization effect. The next step is to conduct experimental research on the inactivation of the influenza virus using a far-UVC 228 nm pulsed laser.

3.
Natl Acad Sci Lett ; 45(4): 343-348, 2022.
Article in English | MEDLINE | ID: covidwho-1943493

ABSTRACT

The proposed paper discusses Far UVC could assassinate microbes without harming healthy tissues. The plasma ion generation will increase the ion (O2 -) generation in abundance along with hydrogen ion (H+), and at the same time, the negative hydroxyl radical (OH-) formed will merge with the positive (H+) ion of the virus to break the structure of it. The silver nanoparticle which is present in the diffuser with thermostat support is very effective for destroying the microbial elements by heating the gel present within the diffuser. The gel will mix in the environment, and it will also increase the activity of T cell generation and act as an immunoglobulin booster in the human body while inhaling it. In the proposed device, we are using warm humidified CO2 strategic therapy in low dose which is able to suppress any microbial element like SARS-CoV2.

4.
Autonomous Systems: Sensors, Processing and Security for Ground, Air, Sea and Space Vehicles and Infrastructure 2022 ; 12115, 2022.
Article in English | Scopus | ID: covidwho-1949889

ABSTRACT

With the global coronavirus pandemic still persisting, the repeated disinfection of large spaces and small rooms has become a priority and matter of focus for researchers and developers. The use of ultraviolet light (UV) for disinfection is not new;however, there are new efforts to make the methods safer, more thorough, and automated. Indeed, continuous very low dose-rate far-UVC light in indoor public locations is a promising, safe and inexpensive tool to reduce the spread of airborne-mediated microbial diseases. This paper investigates the problem of disinfecting surfaces using autonomous mobile robots equipped with UV light towers. In order to demonstrate the feasibility of our autonomous disinfection framework, we also present a teleoperated robotic prototype. It consists of a robotic rover unit base, on which two separate UV light towers carrying 254 nm UVC and 222 nm far-UVC lights are mounted. It also includes a live-feed camera for remote operation, as well as power and communication electronics for the remote operation of the UV lamps. The 222 nm far-UVC light has been recently shown to be non-inammatory and non-photo carcinogenic when radiated on mammalian skin, while still sterilizing the coronavirus on irradiated surfaces. With far-UVC light, disinfection robots may no longer require the evacuation of spaces to be disinfected. The robot demonstrates promising disinfection performance and potential for future autonomous applications. © 2022 SPIE. All rights reserved.

5.
J Occup Environ Hyg ; : 1-14, 2022 Aug 05.
Article in English | MEDLINE | ID: covidwho-1931709

ABSTRACT

The emergence of COVID-19 and its corresponding public health burden has prompted industries to rapidly implement traditional and novel control strategies to mitigate the likelihood of SARS-CoV-2 transmission, generating a surge of interest and application of ultraviolet germicidal irradiation (UVGI) sources as disinfection systems. With this increased attention the need to evaluate the efficacy and safety of these types of devices is paramount. A field study of the early implementation of UVGI devices was conducted at the Space Needle located in Seattle, Washington. Six devices were evaluated, including four low-pressure (LP) mercury-vapor lamp devices for air and surface sanitation not designed for human exposure and two krypton chloride (KrCl*) excimer lamp devices to be operated on and around humans. Emission spectra and ultraviolet (UV) irradiance at different locations from the UV devices were measured and germicidal effectiveness against SARS-CoV-2 was estimated. The human safety of KrCl* excimer devices was also evaluated based on measured irradiance and estimated exposure durations. Our results show all LP devices emitted UV radiation primarily at 254 nm as expected. Both KrCl* excimers emitted far UVC irradiation at 222 nm as advertised but also emitted at longer, more hazardous wavelengths (228 to 262 nm). All LP devices emitted strong UVC irradiance, which was estimated to achieve three log reduction of SARS-CoV-2 within 10 sec of exposure at reasonable working distances. KrCl* excimers, however, emitted much lower irradiance than needed for effective disinfection of SARS-CoV-2 (>90% inactivation) within the typical exposure times. UV fluence from KrCl* excimer devices for employees was below the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Values (TLVs) under the reported device usage and work shifts. However, photosensitive individuals, human susceptibility, or exposure to multiple UV sources throughout a worker's day, were not accounted for in this study. Caution should be used when determining the acceptability of UV exposure to workers in this occupational setting and future work should focus on UVGI sources in public settings.

6.
Viruses ; 14(4)2022 03 25.
Article in English | MEDLINE | ID: covidwho-1820404

ABSTRACT

Recent research using UV radiation with wavelengths in the 200-235 nm range, often referred to as far-UVC, suggests that the minimal health hazard associated with these wavelengths will allow direct use of far-UVC radiation within occupied indoor spaces to provide continuous disinfection. Earlier experimental studies estimated the susceptibility of airborne human coronavirus OC43 exposed to 222-nm radiation based on fitting an exponential dose-response curve to the data. The current study extends the results to a wider range of doses of 222 nm far-UVC radiation and uses a computational model coupling radiation transport and computational fluid dynamics to improve dosimetry estimates. The new results suggest that the inactivation of human coronavirus OC43 within our exposure system is better described using a bi-exponential dose-response relation, and the estimated susceptibility constant at low doses-the relevant parameter for realistic low dose rate exposures-was 12.4 ± 0.4 cm2/mJ, which described the behavior of 99.7% ± 0.05% of the virus population. This new estimate is more than double the earlier susceptibility constant estimates that were based on a single-exponential dose response. These new results offer further evidence as to the efficacy of far-UVC to inactivate airborne pathogens.


Subject(s)
COVID-19 , Coronavirus OC43, Human , Disinfection/methods , Humans , SARS-CoV-2 , Ultraviolet Rays , Virus Inactivation
7.
10th International Conference on Radar, Antenna, Microwave, Electronics, and Telecommunications, ICRAMET 2021 ; : 158-161, 2021.
Article in English | Scopus | ID: covidwho-1709132

ABSTRACT

Emerging of the Coronavirus Disease 2019 (COVID-19) since the end of 2019, calls scientist to develop various ways to combat the disease. One of the possible ways is to develop human friendly sterilization room. We report characterization of far UV-C beam propagation in air medium. Several distances and radiation angles of the far UV-C beam was experimentally measured using an UV optical spectrum meter. As a result, the beam has irradiance loss of 0.02 - 0.2 dB/cm and beam radiation angle of about 150 degree for vertical and 180 degree for horizontal. The far UV-C beam can be used for airborne virus sterilization and safe to human skin or eyes. The exposure time varies to the distance from the UVC source. © 2021 IEEE.

8.
Appl Environ Microbiol ; 87(22): e0153221, 2021 10 28.
Article in English | MEDLINE | ID: covidwho-1494943

ABSTRACT

Effective disinfection technology to combat severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can help reduce viral transmission during the ongoing COVID-19 global pandemic and in the future. UV devices emitting UVC irradiation (200 to 280 nm) have proven to be effective for virus disinfection, but limited information is available for SARS-CoV-2 due to the safety requirements of testing, which is limited to biosafety level 3 (BSL3) laboratories. In this study, inactivation of SARS-CoV-2 in thin-film buffered aqueous solution (pH 7.4) was determined across UVC irradiation wavelengths of 222 to 282 nm from krypton chloride (KrCl*) excimers, a low-pressure mercury-vapor lamp, and two UVC light-emitting diodes. Our results show that all tested UVC devices can effectively inactivate SARS-CoV-2, among which the KrCl* excimer had the best disinfection performance (i.e., highest inactivation rate). The inactivation rate constants of SARS-CoV-2 across wavelengths are similar to those for murine hepatitis virus (MHV) from our previous investigation, suggesting that MHV can serve as a reliable surrogate of SARS-CoV-2 with a lower BSL requirement (BSL2) during UV disinfection tests. This study provides fundamental information on UVC's action on SARS-CoV-2 and guidance for achieving reliable disinfection performance with UVC devices. IMPORTANCE UV light is an effective tool to help stem the spread of respiratory viruses and protect public health in commercial, public, transportation, and health care settings. For effective use of UV, there is a need to determine 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. We found that SARS-CoV-2 can be inactivated effectively using a broad range of UVC wavelengths, and 222 nm provided the best disinfection performance. Interestingly, 222-nm irradiation has been found to be safe for human exposure up to thresholds that are beyond those effective for inactivating viruses. Therefore, applying UV light from KrCl* excimers in public spaces can effectively help reduce viral aerosol or surface-based transmissions.


Subject(s)
Disinfection/methods , SARS-CoV-2/radiation effects , Virus Inactivation/radiation effects , Animals , Bacteriophage phi 6/radiation effects , COVID-19/prevention & control , COVID-19/transmission , Coronavirus 229E, Human/radiation effects , Disinfection/instrumentation , Humans , Mice , Murine hepatitis virus/radiation effects , Ultraviolet Rays
9.
Viruses ; 13(8)2021 07 23.
Article in English | MEDLINE | ID: covidwho-1325790

ABSTRACT

Transmission of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) occurs through respiratory droplets passed directly from person to person or indirectly through fomites, such as common use surfaces or objects. The aim of this study was to determine the virucidal efficacy of blue LED (405 nm) and far-UVC (222 nm) light in comparison to standard UVC (254 nm) irradiation for the inactivation of feline infectious peritonitis virus (FIPV) on different matrices as a model for SARS-CoV-2. Wet or dried FIPV on stainless steel, plastic, or paper discs, in the presence or absence of artificial saliva, were exposed to various wavelengths of light for different time periods (1-90 min). Dual activity of blue LED and far-UVC lights were virucidal for most wet and dried FIPV within 4 to 16 min on all matrices. Individual action of blue LED and far-UVC lights were virucidal for wet FIPV but required longer irradiation times (8-90 min) to reach a 4-log reduction. In comparison, LED (265 nm) and germicidal UVC (254 nm) were virucidal on almost all matrices for both wet and dried FIPV within 1 min exposure. UVC was more effective for the disinfection of surfaces as compared to blue LED and far-UVC individually or together. However, dual action of blue LED and far-UVC was virucidal. This combination of lights could be used as a safer alternative to traditional UVC.


Subject(s)
COVID-19/virology , Coronavirus, Feline/radiation effects , Disinfection/methods , SARS-CoV-2/radiation effects , Animals , COVID-19/prevention & control , Cats , Coronavirus Infections/virology , Coronavirus, Feline/growth & development , Coronavirus, Feline/physiology , Disinfection/instrumentation , Humans , SARS-CoV-2/growth & development , SARS-CoV-2/physiology , Ultraviolet Rays , Virus Inactivation/radiation effects
10.
GMS Hyg Infect Control ; 16: Doc07, 2021.
Article in English | MEDLINE | ID: covidwho-1107383

ABSTRACT

Background: The ongoing coronavirus pandemic requires new disinfection approaches, especially for airborne viruses. The 254 nm emission of low-pressure vacuum lamps is known for its antimicrobial effect, but unfortunately, this radiation is also harmful to human cells. Some researchers published reports that short-wavelength ultraviolet light in the spectral region of 200-230 nm (far-UVC) should inactivate pathogens without harming human cells, which might be very helpful in many applications. Methods: 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. Results: 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. Conclusion: The approach is very promising, especially for temporary applications, but the data is still sparse. Investigations with high far-UVC doses over a longer period of time have not yet been carried out, and there is no positive study on the impact of this radiation on human eyes. Additionally, far-UVC sources are unavailable in larger quantities. Therefore, this is not a short-term solution for the current pandemic, but may be suitable for future technological approaches for decontamination in rooms in the presence of people or for antisepsis.

11.
Photodiagnosis Photodyn Ther ; 33: 102184, 2021 Mar.
Article in English | MEDLINE | ID: covidwho-1039523

ABSTRACT

BACKGROUND: The effectiveness of 222 nm ultraviolet (UV) C light for disinfecting surfaces contaminated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been reported. The aim of this study was to evaluate the effect of the intermittent irradiation of 222 nm UVC on SARS-CoV-2 and the fluence-dependent effect of 222 nm UVC irradiation on SARS-CoV-2 inactivation. METHODS: We experimented with 5 min continuous and intermittent irradiation for 0.1, 0.05, 0.013, and 0.003 mW/cm2 of 222 nm UVC to evaluate the differences in the effect of the continuous and intermittent irradiation of 222 nm UVC on SARS-CoV-2 inactivation. For intermittent irradiation, we followed the on-off irradiation cycles with every 10-s irradiation followed by a 380-s interval. Thereafter, we evaluated the effects of 0.1, 0.013, and 0.003 mW/cm2 222 nm UVC irradiation on SARS-CoV-2 contamination at UV fluences of 1, 2, and 3 mJ/cm2 at each irradiance. RESULTS: At each irradiance, no significant difference was observed in the log reduction of SARS-CoV-2 between continuous and intermittent irradiation. At each UV fluence, no significant difference was observed in the log reduction of SARS-CoV-2 among the three different irradiance levels. CONCLUSION: There was no significant difference between continuous and intermittent irradiation with 222 nm UVC with regards to SARS-CoV-2 inactivation. Moreover, 222 nm UVC inactivates SARS-CoV-2 in a fluence-dependent manner. The efficacy of 222-nm UVC irradiation in reducing the contamination of SARS-CoV-2 needs to be further evaluated in a real-world setting.


Subject(s)
Disinfection/methods , SARS-CoV-2/radiation effects , Ultraviolet Rays , Humans , Virus Inactivation
12.
Am J Infect Control ; 49(3): 299-301, 2021 03.
Article in English | MEDLINE | ID: covidwho-743831

ABSTRACT

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), has emerged as a serious threat to human health worldwide. Efficient disinfection of surfaces contaminated with SARS-CoV-2 may help prevent its spread. This study aimed to investigate the in vitro efficacy of 222-nm far-ultraviolet light (UVC) on the disinfection of SARS-CoV-2 surface contamination. METHODS: We investigated the titer of SARS-CoV-2 after UV irradiation (0.1 mW/cm2) at 222 nm for 10-300 seconds using the 50% tissue culture infectious dose (TCID50). In addition, we used quantitative reverse transcription polymerase chain reaction to quantify SARS-CoV-2 RNA under the same conditions. RESULTS: One and 3 mJ/cm2 of 222-nm UVC irradiation (0.1 mW/cm2 for 10 and 30 seconds) resulted in 88.5 and 99.7% reduction of viable SARS-CoV-2 based on the TCID50 assay, respectively. In contrast, the copy number of SARS-CoV-2 RNA did not change after UVC irradiation even after a 5-minute irradiation. CONCLUSIONS: This study shows the efficacy of 222-nm UVC irradiation against SARS-CoV-2 contamination in an in vitro experiment. Further evaluation of the safety and efficacy of 222-nm UVC irradiation in reducing the contamination of real-world surfaces and the potential transmission of SARS-CoV-2 is needed.


Subject(s)
Decontamination/methods , Disinfection/methods , RNA, Viral/radiation effects , SARS-CoV-2/radiation effects , Ultraviolet Rays , COVID-19/prevention & control , COVID-19/virology , Humans
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