>>8929239 LB
The ozone layer (Oxygen3 gas) blocks much of UV-A rays (50%), most of UV-B (90%), and all of UV-C (99%). pic related.
https://sciencing.com/percent-uv-ozone-absorb-20509.html
Wavelengths below ~190nm get into the UV-V range, which actually creates ozone when it hits the atmosphere.
https://www.uvonair.com/about-ozone
My guess for the UV light treatment is probably UV-B/C wavelengths due to how common they are and easily manufactured. (easy to find lightbulbs that produce 254nm UVC and UV-B bulbs)
https://ultraviolet.com/what-is-germicidal-ultraviolet/
The problem with these wavelengths is that they are harmful to human skin as well.
The best/safest is Far UV-C, specifically 222nm. pic related.
https://www.rfsafe.com/207-222-nm-uvc-light-can-slow-spread-of-novel-coronavirus-covid-19/
and a study of 222nm light on light sensitive mice… 222nm is safe for skin.
https://onlinelibrary.wiley.com/doi/10.1111/php.13269
Each virus and bacteria have a peak absorption rate that will be close but different from each other. Not only that but the amount of energy required (exposure time) is different.
https://www.americanairandwater.com/uv-facts/uv-dosage.htm
However, with other research on the effectiveness of 222nm, we can see that it completely ruptures some bacteria (Bacillus atrophaeus - Pic related).
Most other traditional UVC (254nm+) simply deactivates the DNA of these microbes.
https://sterilray.com/science/lab-reports/#micrograph