5 ms·

> Standard germicidal UV-C lights are ~250nm. The article is about KrCl 222-nm lights, which people want because they're safe [1] to shine on people, unlike Hg

by jefftk 4y ago

> Standard germicidal UV-C lights are ~250nm. The article is about KrCl 222-nm lights, which people want because they're safe [1] to shine on people, unlike Hg 254-nm lights. [1] Probably -- I'd like to seem some specific additional experiments before widespread deployment.

lazide 4y ago
222nm is not safe to shine on anyone! It will definitely cause skin cancer. 254nm is also not safe. 254nm destroys ozone, interestingly. 240nm and smaller (160nm being the highest producing freq.) produce ozone. [https://onlinelibrary.wiley.com/doi/full/10.1111/php.13391 https://onlinelibrary.wiley.com/doi/full/10.1111/php.13391]
- jefftk 4y ago
  I don't see anything in your link about 222nm causing skin cancer? It's short enough that it shouldn't be getting through the outermost layer of skin, which is dead.
  - lazide 4y ago
    Welders have plenty of experience to contradict it. UV-C is usually blocked by the atmosphere, and most people don't get exposed to it directly - so it rarely comes up. But if you're sitting next to a UV-C generator, don't. It cleaves DNA the same as UV-B, and there is no reason to think it isn't cancer causing. There are a number of areas that can get exposed that have very thin epidermis, or none at all (eyes), though eyes would get retinal keratosis not cancer. That said, hopefully no one is spending enough time close to a high enough power UV-C source for this to REALLY be a problem. Welding Cite - [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5640727/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5640727/] Notably, while having a higher skin cancer risk despite being inside a lot (shop welders, not shipyard welders), the vast majority of welders in that sampled population will have been wearing heavy protective clothing continuously. There was a noticeable increase in risk of skin cancer on the neck, which is one of the few areas that is not always adequately covered. Anecdotally, I knew folks who didn't wear proper full coverage PPE when welding and welded a lot (auto body repair in one case, farm equipment repair in another), and both died in their early 40's from multiple malignant melanomas. One of them, it was 10+ all at once, and he died in less than a year. No one was surprised, unfortunately. They were ALWAYS sunburned from it, and they didn't spend a huge amount of time outside otherwise. That is a pretty broad spectrum source though. UV-C As Potentially Mutagenic/Causing Damage not caught by normal replication suppression mechanisms - [https://pubmed.ncbi.nlm.nih.gov/9951833/ https://pubmed.ncbi.nlm.nih.gov/9951833/] UV-C will also have no problem converting all sorts of organic chemicals into interesting, and often more toxic versions (albeit killing any organisms relying on their original structure in the process), same as UV-B or UV-A.
    - amluto 4y ago
      And yet Far-UVC seems quite safe for people. Presumably what’s going on is that longer wavelength UVC from welding is extremely dangerous.
    - the8472 4y ago
      welding light is broad-spectrum, so it's not relevant when comparing to a narrow-peak light source. > UV-C As Potentially Mutagenic/Causing Damage not caught by normal replication suppression mechanisms - [https://pubmed.ncbi.nlm.nih.gov/9951833/ https://pubmed.ncbi.nlm.nih.gov/9951833/] p53-/- human keratinocyte cell line means that those were in vitro experiments which don't account for the wavelength-dependent penetration depth, which is the point of discussion here.
    - jefftk 4y ago
      None of your links are about 222nm; they're all about longer wavelengths or mixes that include longer wavelengths.
      - daniel_reetz 4y ago
        Let's be clear here. Nothing outside of some extremely filtered high end equipment is producing exactly and only 222nm light, and no cancer study is isolating exactly and only 222nm light. Except in extreme cases all light sources have some bandwidth. Most UV generators produce tens to hundreds of nm of bandwidth. A common MIG or TIG welder produces plenty of 222nm light in a broad distribution* of UV. UV lamps for curing applications have used arcs to generate deep UV for ages. Lack of a particular study for a particular 1nm band is not a meaningful signal. *Source: https://www.ehime-iinet.or.jp/ehime_e/corp/toyo/ronbun/images/r01.gif https://www.ehime-iinet.or.jp/ehime_e/corp/toyo/ronbun/image...
        jefftk 4y ago
        I agree welding is very broad spectrum, including both 222-nm and many other frequencies, and also dangerous. But these KrCl excimer 222-nm products generate light through a completely different mechanism and produce a far narrower spectrum. See https://pubs.acs.org/doi/10.1021/acsphotonics.2c00041 https://pubs.acs.org/doi/10.1021/acsphotonics.2c00041 and specifically this chart https://pubs.acs.org/cms/10.1021/acsphotonics.2c00041/asset/images/medium/ph2c00041_0007.gif https://pubs.acs.org/cms/10.1021/acsphotonics.2c00041/asset/... We do know a lot about how dangerous different frequencies are, and when you combine the "risk to humans" curve with the "emissions by wavelength" curve you get very low risk. I do still think we should run additional experiments here before rolling this out broadly for hours-a-day usage, but from what we know so far it looks very good.
- bsder 4y ago
  > 222nm is not safe to shine on anyone! It will definitely cause skin cancer. The whole point of using 222nm is that it doesn't cause effects on either the eyes or the skin. Consequently, you can use it at higher concentrations without worrying about the leakage. The issue, as I understand it, is simply that we don't have a decent LED monochomatic source. All of the currently available sources have broad spectrums that have to be filtered out.
  - hedora 4y ago
    The claim that 222nm is an effective disinfectant seems to directly contradict the claim that it cannot penetrate skin. In particular, if it bounces off dead skin cells, and the environment contains dust, how can it possibly kill things on the dark side of the dust particles? On top of that, reasonable disinfectant timeframes are a few minutes to a few hours, tops. Safety timeframes for human exposures need to be measured in decades if this technology catches on. Claims that lethal dosages of 222nm will penetrate typical glops of pathogens in the environment in seconds, but that cancer causing dosages will not penetrate human skin over years are extraordinary. Extraordinary claims require extraordinary evidence. Are there long term safety trials for this technology? The article claims “reduced damage” in the abstract, implying routine 222 nm exposure is unsafe.
    - scotty79 4y ago
      It's basically because viruses and harmful bacteria are smaller than our dead skin layer. So the light gets into them and destroys their DNA/RNA.
      - harvie 4y ago
        but viruses and bacteria are probably never traveling alone. imagine someone sneezing on table. they will be embeded in pieces of dead skin or tiny droplets of phlegm, saliva, etc... in the linked article they are using it to disinfect surfaces in passenger aircraft. unless it can penetrate a bit, i don't see how it can be effective. also viruses (eg. HIV, Coronavirii,...) are often killed by oxygen in air, dry out or die in other ways when not floating in bodily fluids.

by jefftk 4y ago

lazide 4y ago

222nm is not safe to shine on anyone! It will definitely cause skin cancer. 254nm is also not safe. 254nm destroys ozone, interestingly. 240nm and smaller (160nm being the highest producing freq.) produce ozone. [https://onlinelibrary.wiley.com/doi/full/10.1111/php.13391 https://onlinelibrary.wiley.com/doi/full/10.1111/php.13391]

jefftk 4y ago
I don't see anything in your link about 222nm causing skin cancer? It's short enough that it shouldn't be getting through the outermost layer of skin, which is dead.
- lazide 4y ago
  Welders have plenty of experience to contradict it. UV-C is usually blocked by the atmosphere, and most people don't get exposed to it directly - so it rarely comes up. But if you're sitting next to a UV-C generator, don't. It cleaves DNA the same as UV-B, and there is no reason to think it isn't cancer causing. There are a number of areas that can get exposed that have very thin epidermis, or none at all (eyes), though eyes would get retinal keratosis not cancer. That said, hopefully no one is spending enough time close to a high enough power UV-C source for this to REALLY be a problem. Welding Cite - [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5640727/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5640727/] Notably, while having a higher skin cancer risk despite being inside a lot (shop welders, not shipyard welders), the vast majority of welders in that sampled population will have been wearing heavy protective clothing continuously. There was a noticeable increase in risk of skin cancer on the neck, which is one of the few areas that is not always adequately covered. Anecdotally, I knew folks who didn't wear proper full coverage PPE when welding and welded a lot (auto body repair in one case, farm equipment repair in another), and both died in their early 40's from multiple malignant melanomas. One of them, it was 10+ all at once, and he died in less than a year. No one was surprised, unfortunately. They were ALWAYS sunburned from it, and they didn't spend a huge amount of time outside otherwise. That is a pretty broad spectrum source though. UV-C As Potentially Mutagenic/Causing Damage not caught by normal replication suppression mechanisms - [https://pubmed.ncbi.nlm.nih.gov/9951833/ https://pubmed.ncbi.nlm.nih.gov/9951833/] UV-C will also have no problem converting all sorts of organic chemicals into interesting, and often more toxic versions (albeit killing any organisms relying on their original structure in the process), same as UV-B or UV-A.
  - amluto 4y ago
    And yet Far-UVC seems quite safe for people. Presumably what’s going on is that longer wavelength UVC from welding is extremely dangerous.
  - the8472 4y ago
    welding light is broad-spectrum, so it's not relevant when comparing to a narrow-peak light source. > UV-C As Potentially Mutagenic/Causing Damage not caught by normal replication suppression mechanisms - [https://pubmed.ncbi.nlm.nih.gov/9951833/ https://pubmed.ncbi.nlm.nih.gov/9951833/] p53-/- human keratinocyte cell line means that those were in vitro experiments which don't account for the wavelength-dependent penetration depth, which is the point of discussion here.
  - jefftk 4y ago
    None of your links are about 222nm; they're all about longer wavelengths or mixes that include longer wavelengths.
    - daniel_reetz 4y ago
      Let's be clear here. Nothing outside of some extremely filtered high end equipment is producing exactly and only 222nm light, and no cancer study is isolating exactly and only 222nm light. Except in extreme cases all light sources have some bandwidth. Most UV generators produce tens to hundreds of nm of bandwidth. A common MIG or TIG welder produces plenty of 222nm light in a broad distribution* of UV. UV lamps for curing applications have used arcs to generate deep UV for ages. Lack of a particular study for a particular 1nm band is not a meaningful signal. *Source: https://www.ehime-iinet.or.jp/ehime_e/corp/toyo/ronbun/images/r01.gif https://www.ehime-iinet.or.jp/ehime_e/corp/toyo/ronbun/image...
      - jefftk 4y ago
        I agree welding is very broad spectrum, including both 222-nm and many other frequencies, and also dangerous. But these KrCl excimer 222-nm products generate light through a completely different mechanism and produce a far narrower spectrum. See https://pubs.acs.org/doi/10.1021/acsphotonics.2c00041 https://pubs.acs.org/doi/10.1021/acsphotonics.2c00041 and specifically this chart https://pubs.acs.org/cms/10.1021/acsphotonics.2c00041/asset/images/medium/ph2c00041_0007.gif https://pubs.acs.org/cms/10.1021/acsphotonics.2c00041/asset/... We do know a lot about how dangerous different frequencies are, and when you combine the "risk to humans" curve with the "emissions by wavelength" curve you get very low risk. I do still think we should run additional experiments here before rolling this out broadly for hours-a-day usage, but from what we know so far it looks very good.
bsder 4y ago
> 222nm is not safe to shine on anyone! It will definitely cause skin cancer. The whole point of using 222nm is that it doesn't cause effects on either the eyes or the skin. Consequently, you can use it at higher concentrations without worrying about the leakage. The issue, as I understand it, is simply that we don't have a decent LED monochomatic source. All of the currently available sources have broad spectrums that have to be filtered out.
- hedora 4y ago
  The claim that 222nm is an effective disinfectant seems to directly contradict the claim that it cannot penetrate skin. In particular, if it bounces off dead skin cells, and the environment contains dust, how can it possibly kill things on the dark side of the dust particles? On top of that, reasonable disinfectant timeframes are a few minutes to a few hours, tops. Safety timeframes for human exposures need to be measured in decades if this technology catches on. Claims that lethal dosages of 222nm will penetrate typical glops of pathogens in the environment in seconds, but that cancer causing dosages will not penetrate human skin over years are extraordinary. Extraordinary claims require extraordinary evidence. Are there long term safety trials for this technology? The article claims “reduced damage” in the abstract, implying routine 222 nm exposure is unsafe.
  - scotty79 4y ago
    It's basically because viruses and harmful bacteria are smaller than our dead skin layer. So the light gets into them and destroys their DNA/RNA.
    - harvie 4y ago
      but viruses and bacteria are probably never traveling alone. imagine someone sneezing on table. they will be embeded in pieces of dead skin or tiny droplets of phlegm, saliva, etc... in the linked article they are using it to disinfect surfaces in passenger aircraft. unless it can penetrate a bit, i don't see how it can be effective. also viruses (eg. HIV, Coronavirii,...) are often killed by oxygen in air, dry out or die in other ways when not floating in bodily fluids.