Using Far-UVC Light To Kill Airborne Human Coronaviruses

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Discussion Overview

The discussion centers on the use of far-UVC light (222 nm wavelength) as a method to kill airborne human coronaviruses, particularly in the context of its safety for human health. Participants explore the implications of recent research findings, the biological effects of far-UVC light, and the potential for its application in reducing airborne transmission of viruses.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants highlight that far-UVC light has a limited penetration depth, which may reduce its harmful effects on human cells, particularly in the skin and eyes.
  • Others reference studies indicating that far-UVC light can effectively kill bacteria without causing DNA damage to human skin.
  • Concerns are raised about the potential for corneal damage in rabbits from far-UVC exposure, suggesting caution regarding human exposure without eye protection.
  • Participants discuss the importance of dosage and wavelength in assessing the safety and effectiveness of UVC light, noting that energy alone does not account for the varying effects of different wavelengths.
  • Some mention the generation of ozone as a potential safety issue when using far-UVC in occupied spaces.

Areas of Agreement / Disagreement

Participants express a range of views regarding the safety of far-UVC light for human health, particularly concerning eye exposure. There is no consensus on the long-term effects or the safety of exposure without protection, and multiple competing perspectives on the evidence presented are evident.

Contextual Notes

Limitations include varying interpretations of existing studies, the complexity of measuring biological effects across different wavelengths, and the potential for confounding factors in older medical literature.

Who May Find This Useful

This discussion may be of interest to researchers in the fields of health physics, virology, and public health, as well as those exploring innovative methods for reducing airborne pathogens.

  • #31
ZapperZ said:
Er... isn't this the exact paper that I cited in the very first post of this thread?

Sorry, I picked the wrong thread, and I don't know how to delete my post.
 
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  • #32
ZapperZ said:
I'm not sure how path lengths have anything to do with ozone production

With a weak absorber like O2, a photon needs a lot of encounters with the molecule to have a fair probability of being absorbed. You get that passing through miles of atmosphere, but not in passing across a room.

Far-UV-C doesn't penetrate to skin cells' DNA, but that happens because it gets absorbed and deposits its considerable energy in the outermost layers of the skin. That will surely lead to photochemcal damage, but it's dead skin that's going to be shed anyhow, so overall, it's "safe". The cornea is another matter - it can repair itself, but there's no sacrificial layer, so at best we're talking about reversible damage, quite possibly with considerable discomfort. Eyeglasses or goggles would be highly advisable, but at least they don't have to be specialized UV filters.
Keep in mind that the proposed use, as a preventative measure, calls for constant, all-day exposure.
This raises the question of everything else in the room: Metals will be unaffected, but fabrics, paints, plastics, and surface finishes of all kinds will suffer from prolonged exposure. This, I think, is what makes far-UV-C illumination impractical in most environments. At best, you could circulate the room's air through an enclosed irradiator, reducing but not entirely eliminating airborne pathogens. Whether or not it affords effective protection from SARS-CoV-2, I bet you could get rich selling such units.
 
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  • #34
James Demers said:
With a weak absorber like O2, a photon needs a lot of encounters with the molecule to have a fair probability of being absorbed. You get that passing through miles of atmosphere, but not in passing across a room.

Far-UV-C doesn't penetrate to skin cells' DNA, but that happens because it gets absorbed and deposits its considerable energy in the outermost layers of the skin. That will surely lead to photochemcal damage, but it's dead skin that's going to be shed anyhow, so overall, it's "safe". The cornea is another matter - it can repair itself, but there's no sacrificial layer, so at best we're talking about reversible damage, quite possibly with considerable discomfort. Eyeglasses or goggles would be highly advisable, but at least they don't have to be specialized UV filters.
Keep in mind that the proposed use, as a preventative measure, calls for constant, all-day exposure.
This raises the question of everything else in the room: Metals will be unaffected, but fabrics, paints, plastics, and surface finishes of all kinds will suffer from prolonged exposure. This, I think, is what makes far-UV-C illumination impractical in most environments. At best, you could circulate the room's air through an enclosed irradiator, reducing but not entirely eliminating airborne pathogens. Whether or not it affords effective protection from SARS-CoV-2, I bet you could get rich selling such units.

The layer of tears over the cornea is mostly water which is itself a strong absorber of far UV-C (i.e. 222 nm). Its not exactly a sacrificial layer, but it is readily replenished.

There also isn't a lot of information on the effect of far UV-C light on surfaces and materials. It isn't exactly a common wavelength. Those sources that do emit significant amounts (welding arc, deuterium lamps, etc.) are broad band emitters, so you have to sort out what wavelengths have an effect.
 

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