Far-UVC light efficiently and safely inactivates airborne human coronaviruses
A direct approach to limit airborne transmission of pathogens is to inactivate them within a short time of their production. Germicidal ultraviolet light (UV), typically at 254 nm, is effective in this context, but it is a health hazard to the skin and eyes. By contrast, far-UVC light (207-222 nm) efficiently kills pathogens without harm to exposed human cells or tissues. We previously demonstrated that 222-nm UV light efficiently kills airborne influenza virus (H1N1); here we extend the far-UVC studies to explore efficacy against human coronaviruses from subgroups alpha (HCoV-229E) and beta (HCoV-OC43). We found that low doses of, respectively 1.7 and 1.2 mJ/cm2 inactivated 99.9% of aerosolized alpha coronavirus 229E and beta coronavirus OC43. Based on these results for the beta HCoV-OC43 coronavirus, continuous far-UVC exposure in public locations at the currently recommended exposure limit (3 mJ/cm2/hour) would result in 99.9% viral inactivation in ~ 25 minutes. Increasing the far- UVC intensity by, say, a factor of 2 would halve these disinfection times, while still maintaining safety. As all human coronaviruses have similar genomic size, a key determinant of radiation sensitivity, it is realistic to expect that far-UVC light will show comparable inactivation efficiency against other human coronaviruses, including SARS-CoV-2.
Figure 1
Figure 2
Figure 3
What regulatory exceptions (FDA, etc) are required to install far-uvc lighting in at risk nursing homes?
Dear Dr Buonanno et all.. In this paper in Visual Abstract Table : Far-UV light efficiency and safety Airbone Human Coronaviruses I noticed that at the left-hand side you said that the exposure time to the Far-UVC is 20 seconds, and under the table as the caption, you said that the exposure time is about 21 Minutes. Because this info is absolutely critical and of the most important in your very valuable research, I appreciate it very much if you please clarify for me what is the actual real Exposure Time? Thanks and congratulations on your research. Edber
Are there currently lamps in production? Could represent a group of buyers
I represent a company who can now produce 222 with various sizes of excimer tubes. We are installing them in fixtures next week and sending prototypes to both the EPA and UL for approval the following week. We should be in production shortly thereafter. Also developing an excimer tile which is 1 inch X 1 inch. Happy to discuss
What COMPANY? BRAND?? Hurry hurry hurry, these things should have been fast-tracked months ago!! I can't believe what a missed opportunity....:(
Take a look and talk to Far UV Solutions.
I've Googled Far UV Solutions & found nothing. Got any other more direct links?
Cancel. I figured it out.
Have these lamps been deemed safe to use by any medical body ?
1) It is my understanding that UV light from 100-240 nm produces ozone which can be a respiratory hazard, especialy to the elderly or those already experiencing respiratory issues. Does the far-UVc light being at 222 nm produce hazardous ozone? 2) It is also my understanding that prolonged exposure to UV light can have other negative effects on the body such as premature aging of the skin and a weakening of the immune system, among others. How would this far-UVc light not have similar effects even if it is suggested that it can't prenetrate the skin/eyes and damage DNA?
Hi Mr Adams, 1) During each experiment we run an ozone meter, which never registered ozone above ''noise'' level. 2) In principle, because the far-UVC light does not penetrate the surface layers of skin and eye we would not expect premature aging or weakening of the immune system in the long-term; however, we have not done these experiments yet. Manuela Buonanno
According to Kowalski, W. 2009. Ultraviolet Germicidal Irradiation Handbook. Springer, only UV-C radiation in the range of 175 nm to 210 nm can convert atmospheric oxygen to ozone. Some low-pressure mercury-vapour germicidal lamps can produce small amounts of ozone due to an emission line at 185 nm, but this can be prevented by using sodium-barium or suitably doped fused quartz tubes. The article further notes that the 12-watt Ushio KrCl excimer lamp uses a proprietary optical filtering window to reduce lamp emissions outside of the 222 nm peak emission.
Hello, thank you for your research during these unique times. 1. How does this research compare to your work done in "Far-UVC light: A new tool to control the spread of airborne-mediated microbial disease" published 2.9.18? Is this an extension of the work performed for that paper or is it based on the same experiments? 2. Have you looked at other wavelengths including 210 or 230 to evaluate their effectiveness or is it your claim that all far UV-C wavelengths are equally effective?
Hi Mr. Roth, 1) For this this work, we used the same aerosol chamber as the 2018 influenza A studies; here we investigated the effectiveness of the far-UVC light against two different viruses (alpha and beta human coronavirus). Therefore, this work is an extension of the 2018 study with influenza A. 2) In the study we show that the alpha and beta human coronaviruses are susceptible to 222 nm light. We speculate that they will be susceptible to killing from exposure to other wavelengths of the far-UVC spectrum, but not necessarily equally effective; we have not measured the actual effectiveness of 210 nm or 230 nm light yet.
The units reported are mJ/cm2. How does this measurement convert to the radiant flux to be applied to a cubic cm or cubic meter of air contaminated with virus to achieve 1-log?
Hi Loren, We report radiant exposure in units of mJ/cm^2. To determine the radiant flux you would multiply by the area of the surface (in cm^2) and then divide by the duration of the exposure (in seconds), which gives the units of Watts for the radiant flux. -David Welch
The units reported (mJ/cm2) are technically correct, as you are interested in the amount of energy incident upon the cross-sectional area of the aerosolized droplet from every direction. This is radiant fluence, aka radiant spherical exposure. (The radiant fluence rate is the amount of radiant flux incident upon the cross-sectional area, with units of uW/cm2). It is basically impossible to measure radiant fluence in an experimental setup like this, but it does not matter. The setup consisted of a Ushio excimer lamp with a 4.4 cm x 5.9 cm emission area positioned 22 cm away from a 26 cm x 25.6 cm window. At this distance, the radiation is reasonably parallel, and so measuring the irradiance at the window (90 uW/cm2) provides a reasonable estimate of the radiant fluence rate. There was also a specular reflector on the opposite side of the chamber with a far-UV reflectance of 15 percent (which is surprising -- the reflectance of specular aluminum at 250 nm typically varies between 50 and 90 percent), which the authors reasonably assumed increased the radiant fluence rate to 100 uW/cm2.
Dear Dr Buonanno et al. I have a specific need for your expertise. Do you consult? Thank you, Bill
Dear Mr. Buonanno and team members, I have been studying your work published in the last five years and very excited about your research. Many congratulations for great breakthrough helpful to Mankind. Great work ....Can you please let me know the reason behind not conducting the test directly on SARS-CoV-2 (the virus responsible for pandemic)? It may seem a very primary question to you, please reply if convenient as I could not get an answer for long.
Dear Dr. Shah, thank you for your interest in our research. Indeed, we are currently testing our hypothesis on SARS-CoV-2. Our laboratory is certified to conduct studies using BSL2 (Biosafety Level 2) pathogens such as HCoV-229E and HCoV-OC43. SARS-CoV-2 instead is a BSL3 level pathogen. We have an ongoing collaboration with a team in the BSL3 facility at Columbia University to assess far-UVC efficacy against SARS-CoV-2 as well. Best regards, Manuela Buonanno
Dear Mr. Buonanno, Thanks a lot and I wish you all the best. I hope you may publish results for conventional UV C light also to increase the outreach. Thanking you, Devang Shah
Dear Dr. Buonanno and team, Thank you for the work that you are doing. May I know when we may expect to read about the results from your tests on SARS-CoV-2?
Hi Mr. Ong those studies are still ongoing. Best regards Manuela
Hi, I have a comment regarding following and similar statements written in this paper: "Based on these results for the beta HCoV-OC43 coronavirus, continuous far-UVC exposure in public locations at the currently recommended exposure limit (3 mJ/cm2/hour) would result in 99.9% viral inactivation in ~ 25 minutes." Dose of 3mJ/cm2 you are referring to is derived based on the calculated 8-h occupational hazard in the workplace. This said, it is a daily limit, not 23 mJ/cm2 per 8 h. Public locations are not open to public for only 8h per day. Thus, correct me if I am wrong, but UV dose you are referring to is, either related to intermittent far-UVC exposure in public locations or 8-h-per-day continuous UV irradiation. Thank you
Hi Ms Jovanovic ~3 mJ/cm2/hour refers to the International Commission on Non-Ionizing Radiation Protection and the American Conference of Governmental Industrial Hygienists (ACGIH(R) regulatory limit as to the amount of 222 nm light to which the public can be exposed, which is 23 mJ/cm2 8-h-per-day continuous UV irradiation. Best regards, Manuela Buonanno
I assume the prescribed limit of 23 mJ/cm2 8-hr/day for continuous human exposure accounts for the typical rate of corneal shedding and replacement that would occur during the 16 hours of non-exposure. It may follow that intermittent/periodic exposure totaling 8 hours per day would require an equal amount of corneal self-repair. Accordingly, a similar daily limit might apply in cases of intermittent/periodic exposure. Notably, the findings of 1.2-1.7 mJ/cm2 for achieving 99.9% inactivation would result in exposures greater than 23mJ/cm2 after 13.5 to 19 hours of continuous, or additive intermittent, dosing. Although the likelihood of 24-hours of continuous exposure is highly unlikely, in the absence of a defined 24-hour exposure limit, it may follow that only exposures below 0.96 mJ/cm2 can definitively be deemed safe.
Are there materials that might fluoresce under 222nm UV at potentially dangerous longer UV wavelengths?
hi sorry for this question but I want to be quite sure to understand, according with your article the HCoV-299E can be inactivated in 1 second if I apply a 1.1mW/cm2 and will expect a 99% of effectiveness as well with the HCoV-OC43 applying 0.78mW/cm2, am I correct?
Hello, Anyone have some information about the use of UVC 275 to 287 nm interaction with the Covid-19 Virus?
you are reporting "from the International Commission on Non- Ionizing Radiation Protection (ICNIRP) is 23 mJ/cm2 per 8-hour exposure " that value is wrong, and hard to interpret leading to confusions, the ICNIRP(located on sheet 5 or page 174 from reference 34) has determined that the maximum exposure is 0.1uW/cm2 by a time of 8 hour leading to 28.8mJ/m2 (.0001mW/cm2*28800s where 28800 seconds are the 8 hours of exposition ), then is not a safe exposure 3mJ/cm2/h (0.8uj/cm2) that is eit times bigger than the maximum exposure of 0.1uW/cm according the ICNIRP. Also I have a concern about ozone gas an other poison gasses, in the same reference 34 sheet 16 page 185 says: "It is worthy of note that in addition to the direct hazard of UV exposure, very intense UVC sources (particularly of wavelengths less than 230 nm) may also produce hazardous concentrations of ozone and nitrogen oxides from the airand of phosgene gas in the presence of degreasers; thus,many UV germicidal lamps now have quartz-glass envelopes that block wavelengths below230 nm." so, does 222nm is a safe wavelength ?
Hi Jorge, The table that you are referring to in reference 34 gives the "effective irradiance" which requires multiplication of the radiant exposure by the relative spectral effectiveness. The effective irradiance value is based on the 3.0 mJ/cm^2 limit for 270 nm light. The value the table gives as 0.0001 mW/cm^2 *28800 s is 2.88 mJ/cm^2, not 28.8 as you have listed, which is good approximation. Note that the relative spectral effectiveness of 222 nm light, shown in Table 1 of that same reference, recommends a daily safe exposure of about 23 mJ/cm^2 for the entire 8-hour day. Regarding ozone, while photons with wavelengths less than about 240 nm can react to produce ozone, the probability of this is very small until the wavelength is less than about 200 nm. We have measured ozone concentration next to these lamps during operation and the values were not even close to hazardous levels. -David
and what about phosgene gas and nitrogen oxides? there is no study that confirm that 222nm does not produce that kind of gasses. the unit or dosis or what ever you mean called 3 mJ/cm2/hour, does not exist. you should type like 0.833uW/cm^2 (and you can not expose more than one hour to this dosis according to ICNIRP) now considering your 23mJ/cm^2 we have: 23 mJ/cm^2 per 8h = 230J/m^2 in a interval of 8 hours this mean 230J/m^2 /28800 seconds = 0.007986W/m^2 from reference 34 again: Eeff= E(lamda)*S(lamda)*Delta Lamda S(lamda)=for 210<=lamda <=270 =0.959^(270-lamda)=(0.959^(270-222))=0.134058 E(lamda)= 0.007986W/m^2 Delta Lamda=10 Tipical bandwidth of an eximer lamp after filter(cannot be 1 the perfect one nanometer filter does not exist) Eff=( 0.007986W/m^2 )*0.134058*10= 0.01070W/m^2 from reference 34 : "Permissible exposure time in seconds for exposure to UVR incident upon the unprotected skin or eye may be computed by dividing 30 J/m^2 by the value of Eeff in W/m^2. The maximal exposure duration may also be determined using Table 2, which provides representative exposure durations corresponding to effective irradiances in W/m^2or uW/cm^2." so: 30 J/m^2 / 0.01070W/m^2 = 2803.73 secconds or 46 minutes for ALL DAY. so according to INCIRP you only can be exposed by 46 minutes as maximum per day.
Hi Jorge, You will note that in the application of that equation from reference 34 the value for E(lambda) has units of W/m^2 / nm, not simply W/m^2. If you multiply by a 10 nm bandwidth you need to be sure that you are also accounting for the need to distribute the spectral irradiance value over that same bandwidth, so you need to divide E(lambda) by 10 in this case you describe. This will give you a calculated safe exposure time close to 8 hours. -David
Since 222 nm light does not penetrate the eye or the skin, is the ICNIRP daily maximum dosage even relevant or material? It doesn’t look like their recommendations consider that factor at all.
Good point!!! I hope you are correct, and that this lightning is seen ubiquitous, as this disease is truly crippling us, ...& no vaccination will be coming soon I'm sure.
*SOON not seen, sorry
Posted 27 Apr, 2020
On 24 Jun, 2020
Far-UVC light efficiently and safely inactivates airborne human coronaviruses
Posted 27 Apr, 2020
On 24 Jun, 2020
A direct approach to limit airborne transmission of pathogens is to inactivate them within a short time of their production. Germicidal ultraviolet light (UV), typically at 254 nm, is effective in this context, but it is a health hazard to the skin and eyes. By contrast, far-UVC light (207-222 nm) efficiently kills pathogens without harm to exposed human cells or tissues. We previously demonstrated that 222-nm UV light efficiently kills airborne influenza virus (H1N1); here we extend the far-UVC studies to explore efficacy against human coronaviruses from subgroups alpha (HCoV-229E) and beta (HCoV-OC43). We found that low doses of, respectively 1.7 and 1.2 mJ/cm2 inactivated 99.9% of aerosolized alpha coronavirus 229E and beta coronavirus OC43. Based on these results for the beta HCoV-OC43 coronavirus, continuous far-UVC exposure in public locations at the currently recommended exposure limit (3 mJ/cm2/hour) would result in 99.9% viral inactivation in ~ 25 minutes. Increasing the far- UVC intensity by, say, a factor of 2 would halve these disinfection times, while still maintaining safety. As all human coronaviruses have similar genomic size, a key determinant of radiation sensitivity, it is realistic to expect that far-UVC light will show comparable inactivation efficiency against other human coronaviruses, including SARS-CoV-2.
Figure 1
Figure 2
Figure 3
What regulatory exceptions (FDA, etc) are required to install far-uvc lighting in at risk nursing homes?
Dear Dr Buonanno et all.. In this paper in Visual Abstract Table : Far-UV light efficiency and safety Airbone Human Coronaviruses I noticed that at the left-hand side you said that the exposure time to the Far-UVC is 20 seconds, and under the table as the caption, you said that the exposure time is about 21 Minutes. Because this info is absolutely critical and of the most important in your very valuable research, I appreciate it very much if you please clarify for me what is the actual real Exposure Time? Thanks and congratulations on your research. Edber
Hi Edber, In these tests using the aerosol chamber the exposure time is only 20 seconds, but note that the intensity of this exposure is relatively high (100 uW/cm^2). The calculation of 25 minutes to inactivate 99.9% of virus reflects operation of the lamps at an intensity that is within current ACGIH/INCIRP daily exposure limits for 222 nm light. -David Welch
David, I received your reply "We report radiant exposure in units of mJ/cm^2. To determine the radiant flux you would multiply by the area of the surface (in cm^2) and then divide by the duration of the exposure (in seconds), which gives the units of Watts for the radiant flux. -David Welch" . I am not looking at surface treatment. I am trying to determine mW/cm3 to deactivate virus in a given air volume. I assume we need to deliver a certain amount of energy to disrupt the bongs. I want to understand the dosage of 270nm and/or 225nm required to treat 1-cm3 or 1-m3 of virus ladened air down to 1-log (or 5-log) for human breathing contaminated air (droplet exhale). Can you extrapolate this information from your test data? If you can tell me the air volume exposed at 20 seconds at the 100 uW, that could possibly begin to answer the question. Thank you.
"I am trying to determine mW/cm3 to deactivate virus in a given air volume." What you are asking for here is related to "radiant energy density," an SI unit expressed in joules per cubic meter. You could have "radiant flux density," but this is not a recognized SI unit. I believe what you are asking for is "radiant fluence," aka "radiant spherical exposure," which is defined as "the quotient of the radiant energy of all radiation incident on the outer surface of an infinitely small sphere centred at the given point by the area of the diametrical cross-section of that sphere." This is the appropriate radiometric quantity for describing the irradiation of microorganisms, and it is expressed in Joules per square meter.
you should read this article DOI: 10.1023/A:1013951313398 Mathematical Modeling of Ultraviolet Germicidal Irradiation for Air Disinfection, there is all you need to know.
Are there currently lamps in production? Could represent a group of buyers
I represent a company who can now produce 222 with various sizes of excimer tubes. We are installing them in fixtures next week and sending prototypes to both the EPA and UL for approval the following week. We should be in production shortly thereafter. Also developing an excimer tile which is 1 inch X 1 inch. Happy to discuss
What COMPANY? BRAND?? Hurry hurry hurry, these things should have been fast-tracked months ago!! I can't believe what a missed opportunity....:(
Take a look and talk to Far UV Solutions.
I've Googled Far UV Solutions & found nothing. Got any other more direct links?
Cancel. I figured it out.
Have these lamps been deemed safe to use by any medical body ?
1) It is my understanding that UV light from 100-240 nm produces ozone which can be a respiratory hazard, especialy to the elderly or those already experiencing respiratory issues. Does the far-UVc light being at 222 nm produce hazardous ozone? 2) It is also my understanding that prolonged exposure to UV light can have other negative effects on the body such as premature aging of the skin and a weakening of the immune system, among others. How would this far-UVc light not have similar effects even if it is suggested that it can't prenetrate the skin/eyes and damage DNA?
Hi Mr Adams, 1) During each experiment we run an ozone meter, which never registered ozone above ''noise'' level. 2) In principle, because the far-UVC light does not penetrate the surface layers of skin and eye we would not expect premature aging or weakening of the immune system in the long-term; however, we have not done these experiments yet. Manuela Buonanno
According to Kowalski, W. 2009. Ultraviolet Germicidal Irradiation Handbook. Springer, only UV-C radiation in the range of 175 nm to 210 nm can convert atmospheric oxygen to ozone. Some low-pressure mercury-vapour germicidal lamps can produce small amounts of ozone due to an emission line at 185 nm, but this can be prevented by using sodium-barium or suitably doped fused quartz tubes. The article further notes that the 12-watt Ushio KrCl excimer lamp uses a proprietary optical filtering window to reduce lamp emissions outside of the 222 nm peak emission.
Hello, thank you for your research during these unique times. 1. How does this research compare to your work done in "Far-UVC light: A new tool to control the spread of airborne-mediated microbial disease" published 2.9.18? Is this an extension of the work performed for that paper or is it based on the same experiments? 2. Have you looked at other wavelengths including 210 or 230 to evaluate their effectiveness or is it your claim that all far UV-C wavelengths are equally effective?
Hi Mr. Roth, 1) For this this work, we used the same aerosol chamber as the 2018 influenza A studies; here we investigated the effectiveness of the far-UVC light against two different viruses (alpha and beta human coronavirus). Therefore, this work is an extension of the 2018 study with influenza A. 2) In the study we show that the alpha and beta human coronaviruses are susceptible to 222 nm light. We speculate that they will be susceptible to killing from exposure to other wavelengths of the far-UVC spectrum, but not necessarily equally effective; we have not measured the actual effectiveness of 210 nm or 230 nm light yet.
The units reported are mJ/cm2. How does this measurement convert to the radiant flux to be applied to a cubic cm or cubic meter of air contaminated with virus to achieve 1-log?
Hi Loren, We report radiant exposure in units of mJ/cm^2. To determine the radiant flux you would multiply by the area of the surface (in cm^2) and then divide by the duration of the exposure (in seconds), which gives the units of Watts for the radiant flux. -David Welch
The units reported (mJ/cm2) are technically correct, as you are interested in the amount of energy incident upon the cross-sectional area of the aerosolized droplet from every direction. This is radiant fluence, aka radiant spherical exposure. (The radiant fluence rate is the amount of radiant flux incident upon the cross-sectional area, with units of uW/cm2). It is basically impossible to measure radiant fluence in an experimental setup like this, but it does not matter. The setup consisted of a Ushio excimer lamp with a 4.4 cm x 5.9 cm emission area positioned 22 cm away from a 26 cm x 25.6 cm window. At this distance, the radiation is reasonably parallel, and so measuring the irradiance at the window (90 uW/cm2) provides a reasonable estimate of the radiant fluence rate. There was also a specular reflector on the opposite side of the chamber with a far-UV reflectance of 15 percent (which is surprising -- the reflectance of specular aluminum at 250 nm typically varies between 50 and 90 percent), which the authors reasonably assumed increased the radiant fluence rate to 100 uW/cm2.
Dear Dr Buonanno et al. I have a specific need for your expertise. Do you consult? Thank you, Bill
Dear Mr. Buonanno and team members, I have been studying your work published in the last five years and very excited about your research. Many congratulations for great breakthrough helpful to Mankind. Great work ....Can you please let me know the reason behind not conducting the test directly on SARS-CoV-2 (the virus responsible for pandemic)? It may seem a very primary question to you, please reply if convenient as I could not get an answer for long.
Dear Dr. Shah, thank you for your interest in our research. Indeed, we are currently testing our hypothesis on SARS-CoV-2. Our laboratory is certified to conduct studies using BSL2 (Biosafety Level 2) pathogens such as HCoV-229E and HCoV-OC43. SARS-CoV-2 instead is a BSL3 level pathogen. We have an ongoing collaboration with a team in the BSL3 facility at Columbia University to assess far-UVC efficacy against SARS-CoV-2 as well. Best regards, Manuela Buonanno
Dear Mr. Buonanno, Thanks a lot and I wish you all the best. I hope you may publish results for conventional UV C light also to increase the outreach. Thanking you, Devang Shah
Dear Dr. Buonanno and team, Thank you for the work that you are doing. May I know when we may expect to read about the results from your tests on SARS-CoV-2?
Hi Mr. Ong those studies are still ongoing. Best regards Manuela
Hi, I have a comment regarding following and similar statements written in this paper: "Based on these results for the beta HCoV-OC43 coronavirus, continuous far-UVC exposure in public locations at the currently recommended exposure limit (3 mJ/cm2/hour) would result in 99.9% viral inactivation in ~ 25 minutes." Dose of 3mJ/cm2 you are referring to is derived based on the calculated 8-h occupational hazard in the workplace. This said, it is a daily limit, not 23 mJ/cm2 per 8 h. Public locations are not open to public for only 8h per day. Thus, correct me if I am wrong, but UV dose you are referring to is, either related to intermittent far-UVC exposure in public locations or 8-h-per-day continuous UV irradiation. Thank you
Hi Ms Jovanovic ~3 mJ/cm2/hour refers to the International Commission on Non-Ionizing Radiation Protection and the American Conference of Governmental Industrial Hygienists (ACGIH(R) regulatory limit as to the amount of 222 nm light to which the public can be exposed, which is 23 mJ/cm2 8-h-per-day continuous UV irradiation. Best regards, Manuela Buonanno
I assume the prescribed limit of 23 mJ/cm2 8-hr/day for continuous human exposure accounts for the typical rate of corneal shedding and replacement that would occur during the 16 hours of non-exposure. It may follow that intermittent/periodic exposure totaling 8 hours per day would require an equal amount of corneal self-repair. Accordingly, a similar daily limit might apply in cases of intermittent/periodic exposure. Notably, the findings of 1.2-1.7 mJ/cm2 for achieving 99.9% inactivation would result in exposures greater than 23mJ/cm2 after 13.5 to 19 hours of continuous, or additive intermittent, dosing. Although the likelihood of 24-hours of continuous exposure is highly unlikely, in the absence of a defined 24-hour exposure limit, it may follow that only exposures below 0.96 mJ/cm2 can definitively be deemed safe.
Are there materials that might fluoresce under 222nm UV at potentially dangerous longer UV wavelengths?
hi sorry for this question but I want to be quite sure to understand, according with your article the HCoV-299E can be inactivated in 1 second if I apply a 1.1mW/cm2 and will expect a 99% of effectiveness as well with the HCoV-OC43 applying 0.78mW/cm2, am I correct?
Hello, Anyone have some information about the use of UVC 275 to 287 nm interaction with the Covid-19 Virus?
you are reporting "from the International Commission on Non- Ionizing Radiation Protection (ICNIRP) is 23 mJ/cm2 per 8-hour exposure " that value is wrong, and hard to interpret leading to confusions, the ICNIRP(located on sheet 5 or page 174 from reference 34) has determined that the maximum exposure is 0.1uW/cm2 by a time of 8 hour leading to 28.8mJ/m2 (.0001mW/cm2*28800s where 28800 seconds are the 8 hours of exposition ), then is not a safe exposure 3mJ/cm2/h (0.8uj/cm2) that is eit times bigger than the maximum exposure of 0.1uW/cm according the ICNIRP. Also I have a concern about ozone gas an other poison gasses, in the same reference 34 sheet 16 page 185 says: "It is worthy of note that in addition to the direct hazard of UV exposure, very intense UVC sources (particularly of wavelengths less than 230 nm) may also produce hazardous concentrations of ozone and nitrogen oxides from the airand of phosgene gas in the presence of degreasers; thus,many UV germicidal lamps now have quartz-glass envelopes that block wavelengths below230 nm." so, does 222nm is a safe wavelength ?
Hi Jorge, The table that you are referring to in reference 34 gives the "effective irradiance" which requires multiplication of the radiant exposure by the relative spectral effectiveness. The effective irradiance value is based on the 3.0 mJ/cm^2 limit for 270 nm light. The value the table gives as 0.0001 mW/cm^2 *28800 s is 2.88 mJ/cm^2, not 28.8 as you have listed, which is good approximation. Note that the relative spectral effectiveness of 222 nm light, shown in Table 1 of that same reference, recommends a daily safe exposure of about 23 mJ/cm^2 for the entire 8-hour day. Regarding ozone, while photons with wavelengths less than about 240 nm can react to produce ozone, the probability of this is very small until the wavelength is less than about 200 nm. We have measured ozone concentration next to these lamps during operation and the values were not even close to hazardous levels. -David
and what about phosgene gas and nitrogen oxides? there is no study that confirm that 222nm does not produce that kind of gasses. the unit or dosis or what ever you mean called 3 mJ/cm2/hour, does not exist. you should type like 0.833uW/cm^2 (and you can not expose more than one hour to this dosis according to ICNIRP) now considering your 23mJ/cm^2 we have: 23 mJ/cm^2 per 8h = 230J/m^2 in a interval of 8 hours this mean 230J/m^2 /28800 seconds = 0.007986W/m^2 from reference 34 again: Eeff= E(lamda)*S(lamda)*Delta Lamda S(lamda)=for 210<=lamda <=270 =0.959^(270-lamda)=(0.959^(270-222))=0.134058 E(lamda)= 0.007986W/m^2 Delta Lamda=10 Tipical bandwidth of an eximer lamp after filter(cannot be 1 the perfect one nanometer filter does not exist) Eff=( 0.007986W/m^2 )*0.134058*10= 0.01070W/m^2 from reference 34 : "Permissible exposure time in seconds for exposure to UVR incident upon the unprotected skin or eye may be computed by dividing 30 J/m^2 by the value of Eeff in W/m^2. The maximal exposure duration may also be determined using Table 2, which provides representative exposure durations corresponding to effective irradiances in W/m^2or uW/cm^2." so: 30 J/m^2 / 0.01070W/m^2 = 2803.73 secconds or 46 minutes for ALL DAY. so according to INCIRP you only can be exposed by 46 minutes as maximum per day.
Hi Jorge, You will note that in the application of that equation from reference 34 the value for E(lambda) has units of W/m^2 / nm, not simply W/m^2. If you multiply by a 10 nm bandwidth you need to be sure that you are also accounting for the need to distribute the spectral irradiance value over that same bandwidth, so you need to divide E(lambda) by 10 in this case you describe. This will give you a calculated safe exposure time close to 8 hours. -David
Since 222 nm light does not penetrate the eye or the skin, is the ICNIRP daily maximum dosage even relevant or material? It doesn’t look like their recommendations consider that factor at all.
Good point!!! I hope you are correct, and that this lightning is seen ubiquitous, as this disease is truly crippling us, ...& no vaccination will be coming soon I'm sure.
*SOON not seen, sorry
David Welch
replied on 11 May, 2020
Hi Edber, In these tests using the aerosol chamber the exposure time is only 20 seconds, but note that the intensity of this exposure is relatively high (100 uW/cm^2). The calculation of 25 minutes to inactivate 99.9% of virus reflects operation of the lamps at an intensity that is within current ACGIH/INCIRP daily exposure limits for 222 nm light. -David Welch
View 1 reply
Loren Hoboy
replied on 08 June, 2020
David, I received your reply "We report radiant exposure in units of mJ/cm^2. To determine the radiant flux you would multiply by the area of the surface (in cm^2) and then divide by the duration of the exposure (in seconds), which gives the units of Watts for the radiant flux. -David Welch" . I am not looking at surface treatment. I am trying to determine mW/cm3 to deactivate virus in a given air volume. I assume we need to deliver a certain amount of energy to disrupt the bongs. I want to understand the dosage of 270nm and/or 225nm required to treat 1-cm3 or 1-m3 of virus ladened air down to 1-log (or 5-log) for human breathing contaminated air (droplet exhale). Can you extrapolate this information from your test data? If you can tell me the air volume exposed at 20 seconds at the 100 uW, that could possibly begin to answer the question. Thank you.
View 2 replies
Ian Ashdown
replied on 16 June, 2020
"I am trying to determine mW/cm3 to deactivate virus in a given air volume." What you are asking for here is related to "radiant energy density," an SI unit expressed in joules per cubic meter. You could have "radiant flux density," but this is not a recognized SI unit. I believe what you are asking for is "radiant fluence," aka "radiant spherical exposure," which is defined as "the quotient of the radiant energy of all radiation incident on the outer surface of an infinitely small sphere centred at the given point by the area of the diametrical cross-section of that sphere." This is the appropriate radiometric quantity for describing the irradiation of microorganisms, and it is expressed in Joules per square meter.
Jorge Ferreira
replied on 18 June, 2020
you should read this article DOI: 10.1023/A:1013951313398 Mathematical Modeling of Ultraviolet Germicidal Irradiation for Air Disinfection, there is all you need to know.