3 ms·

A few minutes of UV light kill the virus? This is the first I’ve heard, can you link to a citation?

dragontamer 6y ago
I don't have a citation. But it should be noted that COVID19 is an RNA virus. Its a stray piece of RNA floating around in the air, without any cell walls, cell membranes, or other apparatus for protection. As such, any environmental effect: heat, dryness, humidity, UV-light, or chemicals, will kill the virus extremely quickly. ---------- With that being said: E. Coli can still grow on a mask, and I would recommend proper sanitation of your masks. A "standard" bacterial infection would still suck, even if it isn't COVID19. So even IF COVID19 dies in minutes to sunlight (a fact that I find plausible, given the very low levels of protections viruses have vs the environment), its a bad idea to aim at "only disinfecting COVID19". There's many fungus, bacteria, AND viruses that can get stuck on a mask. -------- Hydrogen Peroxide has been shown to be a strong anti-viral, anti-bacterial, and anti-fungal agent. Or, toasting your N95 masks in ~180F ovens for 30 minutes also would do the trick. (Again: the higher temperature and time is NOT for the easily killed virus, but for the harder to kill bacteria and fungus) I know that aerosolized H2O2 has been used to recycle / reuse masks in hospitals. I don't know if liquid H2O2 is safe for masks. So I guess the oven-toast methodology is the best I've heard so far. Aerosol H2O2 is toxic however. And unfortunately, I don't recall the percentage that they used for the study (3% is common household grade. But hospitals are known to use 7% or 10% grade for disinfection purposes). H2O2 is also highly reactive, so its possible it damages the mask somehow. But as a cleaning agent, its both cheap and effective (as long as the base material can survive). ---------- For your cloth masks: your standard laundry detergent is a good anti-fungal, anti-bacterial, anti-viral soap. The issue with N95 masks is that they can't survive the laundry or other, more rigorous forms of cleaning. Throw some chlorine bleach into the wash if you want to be extra sure (a 2nd, independent anti-fungal, anti-bacterial, anti-viral chemical for good measure). EDIT: Can someone please explain the downvotes? We have a classic A/B question here. We should NOT only be aiming to kill viruses (which is extremely easy). If we want to protect ourselves while using masks, we should aim at killing viruses, bacteria, AND fungus. That is, all the different micro-organisms that can be found on a mask.
- jamessb 6y ago
  > But it should be noted that COVID19 is an RNA virus. Its a stray piece of RNA floating around in the air, without any cell walls, cell membranes, or other apparatus for protection It is not true that a SARS-CoV-2 virion is just a "piece of RNA" with nothing around it: they are enveloped by a lipid membrane with embedded proteins. See, for example: https://pdb101.rcsb.org/sci-art/goodsell-gallery/coronavirus https://pdb101.rcsb.org/sci-art/goodsell-gallery/coronavirus https://pdb101.rcsb.org/learn/videos/fighting-coronavirus-with-soap https://pdb101.rcsb.org/learn/videos/fighting-coronavirus-wi...
- pbhjpbhj 6y ago
  >But it should be noted that COVID19 is an RNA virus. Its a stray piece of RNA floating around in the air, without any cell walls, cell membranes, or other apparatus for protection. // Your description of Covid19 as being a stray bit of RNA floating around doesn't tally with the fact that it's a coronavirus - the name comes from the morphology, it's encapsulated. Eg: https://en.m.wikipedia.org/wiki/Peplomer https://en.m.wikipedia.org/wiki/Peplomer This might be the reason. I dare say people dismissed your comment based on a headline factual error. I wonder about microwaving; kills most things.
nkurz 6y ago
This is the best article I found after a quick search: https://www.cuimc.columbia.edu/news/far-uvc-light-safely-kills-airborne-coronaviruses https://www.cuimc.columbia.edu/news/far-uvc-light-safely-kil... It says that "Based on their results, the researchers estimate that continuous exposure to far-UVC light at the current regulatory limit would kill 90% of airborne viruses in about 8 minutes, 95% in about 11 minutes, 99% in about 16 minutes, and 99.9% in about 25 minutes." I don't know how the "regulatory limit" compares to sunlight. Also, this is for seasonal coronaviruses rather than specifically SARS-CoV-2, and it's for airborne particles rather than masks. Maybe someone can find something more specific?
- dragontamer 6y ago
  UV-C is deadly and cancerous, even to humans. Fortunately, the Ozone layer blocks UV-C. Unfortunately, that means there's no UV-C on earth's sunlight. (There's plenty of UV-C in space, before the atmosphere blocked it) The sunlight is mostly UV-A, with little bits of UV-B. ------- I would assume that UV-C lights are regulated, because its so dangerous. So the "edge of regulatory limits" would be whats legally allowed. Either way, UV-C is not present on sunlight at the Earth's surface, and therefore incomparable as a comparison point. UV-C is a useful disinfectant when generated by UV-C lights. But you need to be careful not to touch humans with it, since it provably causes cancer. Most UV-C generators I've seen are inside of boxes of some kind: you place an item inside of the box, close the box, and turn on the UV-C generator.
csours 6y ago
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1280232/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1280232/
- joveian 6y ago
  I am likely misunderstanding something here, but from that study it looks like Coronaviruses are the most sensitive to UV of any virus they found measurements for, however because they also have a much larger genome than most they are only the second easiest to deactivate by sunlight. In table 6 they have minutes to a one log decrease in active virus for Filoviridae that is a bit under double the Coronaviridae deactivation in sunlight value (SnS) in Table 2. I'm guessing that value should be linearly comparable that would leave an estimation of about one hour for a one log reduction under the worst conditions they measure in that table (that are all southern US, although the worst value is in April). If I have understood all that correctly, it sounds like a few hours (not minutes) in sunlight should be considered necessary (I'm guessing that would be a few minutes of UV sterilization). Additionally, it seems to me that a mask would not all be equally reachable by sunlight and some parts might not be at all.

I don't have a citation. But it should be noted that COVID19 is an RNA virus. Its a stray piece of RNA floating around in the air, without any cell walls, cell membranes, or other apparatus for protection. As such, any environmental effect: heat, dryness, humidity, UV-light, or chemicals, will kill the virus extremely quickly. ---------- With that being said: E. Coli can still grow on a mask, and I would recommend proper sanitation of your masks. A "standard" bacterial infection would still suck, even if it isn't COVID19. So even IF COVID19 dies in minutes to sunlight (a fact that I find plausible, given the very low levels of protections viruses have vs the environment), its a bad idea to aim at "only disinfecting COVID19". There's many fungus, bacteria, AND viruses that can get stuck on a mask. -------- Hydrogen Peroxide has been shown to be a strong anti-viral, anti-bacterial, and anti-fungal agent. Or, toasting your N95 masks in ~180F ovens for 30 minutes also would do the trick. (Again: the higher temperature and time is NOT for the easily killed virus, but for the harder to kill bacteria and fungus) I know that aerosolized H2O2 has been used to recycle / reuse masks in hospitals. I don't know if liquid H2O2 is safe for masks. So I guess the oven-toast methodology is the best I've heard so far. Aerosol H2O2 is toxic however. And unfortunately, I don't recall the percentage that they used for the study (3% is common household grade. But hospitals are known to use 7% or 10% grade for disinfection purposes). H2O2 is also highly reactive, so its possible it damages the mask somehow. But as a cleaning agent, its both cheap and effective (as long as the base material can survive). ---------- For your cloth masks: your standard laundry detergent is a good anti-fungal, anti-bacterial, anti-viral soap. The issue with N95 masks is that they can't survive the laundry or other, more rigorous forms of cleaning. Throw some chlorine bleach into the wash if you want to be extra sure (a 2nd, independent anti-fungal, anti-bacterial, anti-viral chemical for good measure). EDIT: Can someone please explain the downvotes? We have a classic A/B question here. We should NOT only be aiming to kill viruses (which is extremely easy). If we want to protect ourselves while using masks, we should aim at killing viruses, bacteria, AND fungus. That is, all the different micro-organisms that can be found on a mask.

jamessb 6y ago
> But it should be noted that COVID19 is an RNA virus. Its a stray piece of RNA floating around in the air, without any cell walls, cell membranes, or other apparatus for protection It is not true that a SARS-CoV-2 virion is just a "piece of RNA" with nothing around it: they are enveloped by a lipid membrane with embedded proteins. See, for example: https://pdb101.rcsb.org/sci-art/goodsell-gallery/coronavirus https://pdb101.rcsb.org/sci-art/goodsell-gallery/coronavirus https://pdb101.rcsb.org/learn/videos/fighting-coronavirus-with-soap https://pdb101.rcsb.org/learn/videos/fighting-coronavirus-wi...
pbhjpbhj 6y ago
>But it should be noted that COVID19 is an RNA virus. Its a stray piece of RNA floating around in the air, without any cell walls, cell membranes, or other apparatus for protection. // Your description of Covid19 as being a stray bit of RNA floating around doesn't tally with the fact that it's a coronavirus - the name comes from the morphology, it's encapsulated. Eg: https://en.m.wikipedia.org/wiki/Peplomer https://en.m.wikipedia.org/wiki/Peplomer This might be the reason. I dare say people dismissed your comment based on a headline factual error. I wonder about microwaving; kills most things.

nkurz 6y ago

This is the best article I found after a quick search: https://www.cuimc.columbia.edu/news/far-uvc-light-safely-kills-airborne-coronaviruses https://www.cuimc.columbia.edu/news/far-uvc-light-safely-kil... It says that "Based on their results, the researchers estimate that continuous exposure to far-UVC light at the current regulatory limit would kill 90% of airborne viruses in about 8 minutes, 95% in about 11 minutes, 99% in about 16 minutes, and 99.9% in about 25 minutes." I don't know how the "regulatory limit" compares to sunlight. Also, this is for seasonal coronaviruses rather than specifically SARS-CoV-2, and it's for airborne particles rather than masks. Maybe someone can find something more specific?

dragontamer 6y ago
UV-C is deadly and cancerous, even to humans. Fortunately, the Ozone layer blocks UV-C. Unfortunately, that means there's no UV-C on earth's sunlight. (There's plenty of UV-C in space, before the atmosphere blocked it) The sunlight is mostly UV-A, with little bits of UV-B. ------- I would assume that UV-C lights are regulated, because its so dangerous. So the "edge of regulatory limits" would be whats legally allowed. Either way, UV-C is not present on sunlight at the Earth's surface, and therefore incomparable as a comparison point. UV-C is a useful disinfectant when generated by UV-C lights. But you need to be careful not to touch humans with it, since it provably causes cancer. Most UV-C generators I've seen are inside of boxes of some kind: you place an item inside of the box, close the box, and turn on the UV-C generator.

csours 6y ago

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1280232/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1280232/

joveian 6y ago
I am likely misunderstanding something here, but from that study it looks like Coronaviruses are the most sensitive to UV of any virus they found measurements for, however because they also have a much larger genome than most they are only the second easiest to deactivate by sunlight. In table 6 they have minutes to a one log decrease in active virus for Filoviridae that is a bit under double the Coronaviridae deactivation in sunlight value (SnS) in Table 2. I'm guessing that value should be linearly comparable that would leave an estimation of about one hour for a one log reduction under the worst conditions they measure in that table (that are all southern US, although the worst value is in April). If I have understood all that correctly, it sounds like a few hours (not minutes) in sunlight should be considered necessary (I'm guessing that would be a few minutes of UV sterilization). Additionally, it seems to me that a mask would not all be equally reachable by sunlight and some parts might not be at all.