Made in the USA from U. Many applications can benefit from germicidal UV-C, including those seeking to prevent flu. I am Atlantic Ultraviolet's corporate communication representative; my daily tasks include presenting and distributing valuable research, engineering, sales and marketing content in the area of applied ultraviolet technologies. Join Our Email List. Home Ultraviolet. Learn Here! Interestingly, nm irradiation has been found to be safe for human exposure up to thresholds that are beyond those effective for inactivating viruses.
It is transmitted primarily via respiratory droplets produced while talking, coughing, and sneezing 2. Effective disinfection procedures can help reduce viral transmission, especially in high-risk places, such as hospitals, other health care facilities, and public transportation systems. Compared to other disinfection methods e. One limitation of conventional UVC devices is that they are not safe for human exposure due to adverse effects on human skin and eyes 9 , An average UV fluence of 1.
Despite these prior works, information on UVC inactivation of SARS-CoV-2 is still limited across UV wavelengths and compared to that of surrogate enveloped viruses, primarily due to the safety requirement of testing, which is limited to biosafety level 3 BSL3 laboratories. These values are much higher than the value reported by Robinson et al. Previous studies on aerosol and surface UV disinfection 25 , 26 suggested that viruses in airborne droplets and on surfaces tend to be more susceptible to UVC irradiation.
Recent work with UV nm inactivation of SARS-CoV-2 on surfaces 17 , 20 , 21 and of other coronaviruses in air 12 , however, show very similar inactivation compared to this study, suggesting data for inactivation generated using thin-film aqueous suspensions can represent inactivation of coronaviruses across various media. The nucleic acid and protein absorbance data were reproduced from Ma et al. Dashed lines represent linear regression results computed from experimental data.
Open symbols represent samples with infectivity equal to or less than the detection limits. Solid symbols with a black edge represent two samples overlapping in the plot with the same UV dose response.
Primary emission wavelengths for UVC devices are listed in each panel. An average UV dose of 1. Another study by Heilingloh et al. This divergence from the UV doses reported in numerous other studies is likely due to the significant difference in the experimental setup for UV exposures and calculation for UV fluences.
The inactivation tests reported by Heilingloh et al. Also, no information was given on how the UV irradiance was measured, there was no report of the absorbance of the suspending media, and standardized procedures for UV fluence calculation e. Viral genome damage is likely to be the primary inactivation mechanism for these UVC devices 23 , and SARS-CoV-2 should have similar sensitivities to UV irradiation from these devices due to similar levels of nucleic acid absorbance at their peak emission wavelengths i.
While viral proteins should be slightly more sensitive to UV irradiation from around the nm wavelength 28 , this previous observation did not appear to enhance the effectiveness of the nm LED in the current study. All virus surrogates were previously tested in the identical collimated beam apparatus, except that the quartz lid was not applied for non-BSL3 organisms.
The inactivation rate constants were also calculated following the same data analysis method UV inactivation rate constants of 0. Compared to nonenveloped viruses, use of enveloped viruses like bacteriophage Phi6 is particularly desirable in surface and aerosol disinfection tests to best represent any interactions between the viral envelope and its surrounding environment that may affect viral sensitivity to UVC irradiation 30 , — The mean inactivation rate values are labeled.
While these inactivation data align well with those from previous studies of UV disinfection of coronaviruses in aerosols and dried on surfaces, future work should continue to evaluate UV inactivation of SARS-CoV-2 in aqueous and other media relative to surrogates such as MHV or bacteriophage and expand these comparisons to other disinfectants important to minimizing the transmission of respiratory viruses.
The UV lamps were set up in a bench-scale collimated beam apparatus Fig. Normalized emission spectra for these UV lamps as used in the experiments Fig. UV exposure experiments were performed according to a standard protocol by Bolton and Linden Absorbance for the samples was measured using a UV-Vis spectrophotometer.
The radiometer detector was placed directly under the quartz lid during irradiance measurements at the liquid surface to include any effects from absorption and reflection of the quartz plate.
UVC radiation is commonly used inside air ducts to disinfect the air. This is the safest way to employ UVC radiation because direct UVC exposure to human skin or eyes may cause injuries, and installation of UVC within an air duct is less likely to cause exposure to skin and eyes. There have been reports of skin and eye burns resulting from improper installation of UVC lamps in rooms that humans can occupy.
A: Consider both the risks of UVC lamps to people and objects and the risk of incomplete inactivation of virus. Risks: UVC lamps used for disinfection purposes may pose potential health and safety risks depending on the UVC wavelength, dose, and duration of radiation exposure.
The risk may increase if the unit is not installed properly or used by untrained individuals. It is important to recognize that, generally, UVC cannot inactivate a virus or bacterium if it is not directly exposed to UVC. In other words, the virus or bacterium will not be inactivated if it is covered by dust or soil, embedded in porous surface or on the underside of a surface.
Not all UVC lamps are the same. Lamps may emit very specific UVC wavelengths like nm or nm , or they may emit a broad range of UV wavelengths.
Some lamps also emit visible and infrared radiation. Some lamps emit multiple types of wavelengths. Testing of the lamp can determine whether, and how much, other wavelengths the lamp puts out.
Intriguingly, it was observed that both RNA viruses were able to remain stable at room temperature for at least 24 h, indicating minimal decay which is consistent with previous studies 36 , Previous results for visible light against non-enveloped viruses demonstrated the need for external photosensitizers such as artificial saliva, blood, feces, etc 30 , Without a porphyrin containing medium, we expected little to no inactivation when this virus was irradiated with visible light.
For these measurements, we used the highest available irradiance of 0. As anticipated, we observed only a log 10 0. Our study was conducted using a neutral liquid media composed of PBS without any photosensitizers and we were able to show that visible light can indeed inactivate lipid-enveloped viruses, differing from the theory that states that photosensitizers are a requirement for inactivation.
While these results provide insight into the basic science involved, they were performed within the context of the applied science needed to show the potential impact of this technology upon the current COVID pandemic.
By using safe, commercially practical irradiance levels, our results are more directly translatable to occupied rooms in the clinical environment. Other studies which used visible light-based irradiation have shown similar results in the absence of photosensitizers, indicating the possibility of an alternative inactivation mechanism 23 , 25 , Studies have proposed two theories for this observation primarily due to non nm wavelengths emitted by the source: 1 some amount of — nm emitted from the source is contributing to the viral inactivation 42 , and 2 the presence of UV-A nm within the source.
This wavelength is known to create oxidative stress upon viral capsids Longer wavelengths, such as — nm, have shown inactivation of the murine leukemia virus MRV-A While this is an intriguing study, it used a broad-spectrum lamp with optical filters to selectively identify the spectrum primarily responsible with their results.
Unfortunately, they did not quantify the amount of light using radiometric units within the spectrum of interest used to irradiate the virus. While the transmission profile of the filters used was provided, it does not consider the spectral composition of the source itself making any direct quantitative comparison between our studies impossible. It is interesting to note that they did observe viral inactivation in their controls from wavelengths less than nm confirming the qualitative findings of our study without confirming the specific use of nm.
It is important to note that the control samples used in our study were exposed to the same overhead non nm lights as the irradiated samples and our results are the observed difference between the two demonstrating the contribution from nm over and above that potentially from to nm.
Future experiments can further quantify the potential effect. Another consideration to be addressed is thermal heating of the virus by the LED source. This was confirmed by our thermocouple measurements as stated earlier. Nazari et al. While the total energy delivered was more comparable to that used in our study, they did not make explicit temperature measurements, their analysis ruled out any potential thermal effects. One possible explanation for the observed differences between the enveloped and non-enveloped organisms is absorption of the nm light by the lipid envelope itself.
This could, in turn, lead to the creation of reactive oxygen species causing an oxidative effect or simply destruction of the envelope leading to a denaturing of the organism. This question could serve as the basis for a range of future studies. The results obtained suggest that the performance of visible light against SARS-CoV-2 is similar to other organisms commonly found in the environment such as S. Previous studies have shown that the visible light irradiance levels used in this study 0.
More importantly, this disinfection can operate continuously as it is safe for humans based upon the exposure guidelines in IEC This means that once it has been in use for a period of time, the environment will be cleaner and safer at all future times including when it is occupied by humans. One limitation of this study is that the inactivation assays were performed in static liquid media as opposed to aerosolized droplets.
While the use of visible light in air disinfection has been briefly studied where it was shown that its effectiveness increased approximately fourfold 47 , further studies involving dynamic aerosolization are needed to better understand the true potential of visible light mediated viral inactivation.
In any case, our study shows the increased susceptibility of enveloped respiratory viral pathogens to nm mediated inactivation in the absence of photosensitizers. The irradiances used in this study are very low and might be easily applied to disinfect occupied areas safely and continuously within hospitals, schools, restaurants, offices and other locations.
We have demonstrated the basic science of inactivation of enveloped viruses such as SARS-CoV-2 and Influenza-A using nm visible light within the context of the applied science required for this technology to have an impact upon the current COVID pandemic. Without the need for exogenous photosensitizers and by using safe, commercially practical irradiance levels, our results can be easily translated to the clinical environment. Future work should focus on explaining the difference between the enveloped and non-enveloped results.
This may include transmission electron microscopy TEM , hemagglutination assay HA , or other methods focusing on the potential role that a mediated reaction due to the envelope itself might play. The size of the virion particle may play a role in photoelectric absorption and could be studied for different viral species. We acknowledge that while unlikely, other wavelengths of visible light, beyond — nm may play a role in the inactivation process and future studies should explore this possibility as well.
Finally, the inactivation kinetics of low irradiances could add valuable insight into clinical applications of this technology. Andersen, K. Worldometer, D. COVID coronavirus pandemic. Buitrago-Garcia, D. Occurrence and transmission potential of asymptomatic and presymptomatic SARS-CoV-2 infections: A living systematic review and meta-analysis. PLoS Med. WHO Dehbandi, R. Lancet Microbe 1 , e Van Doremalen, N. PubMed Article Google Scholar. Behzadinasab, S. ACS Appl. Chan, K.
Biryukov, J. Aboubakr, H. Stability of SARS-CoV-2 and other coronaviruses in the environment and on common touch surfaces and the influence of climatic conditions: A review. Smither, S. Experimental aerosol survival of SARS-CoV-2 in artificial saliva and tissue culture media at medium and high humidity.
Microbes Infect. Schuit, M. Kampf, G. Persistence of coronaviruses on inanimate surfaces and their inactivation with biocidal agents. Rutala, W. Disinfection and sterilization in health care facilities: What clinicians need to know. Rathnasinghe, R. Escombe, A. Upper-room ultraviolet light and negative air ionization to prevent tuberculosis transmission. Nakpan, W. Inactivation of bacterial and fungal spores by UV irradiation and gaseous iodine treatment applied to air handling filters.
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