Far-ultraviolet LED designed to kill bacteria and viruses without harming humans

Not that hard to get them, your big box store has them in the pool filter section. In 2020 these instructions came out how to build a UV sterilizer for cheap: https://makezine.com/projects/build-a-diy-uv-c-sterilization...

And no, not safe without precautions.

The research article says "228-nm UV" Looking at https://ehs.lbl.gov/resource/documents/radiation-protection/... that was linked in a sibling comment, it says

> UV-C 220–280[nm] Corneal injuries Photokeratitis Erythema, skin cancer

When the wavelength is shorted, each photon has more energy and as a rule of thumb they are more dangerous.

"Altering DNA" is the usual way to get cancer. One of the photons hit the DNA, it has enough energy to break one of the parts. Sometimes it can be repaired, but other times it cause a small mutation. If you are unlucky and get enough mutations in some of the "correct" spots the cell gets mad and start reproducing uncontrollably and you get cancer. (Sometimes the alteration is caused by a chemical substance, or other thing. Sometimes it's just a bad copy during normal cell reproduction.)

There is some research saying 222nm is safe, yet still disrupts viruses and bacteria. And you can buy lamps at that frequency on Amazon (for like $1700). However it's not like it's been proved safe by a decades worth of testing and use. The LED's at 222nm just became available in the last year or so. I don't think anyone knows the long term consequences. Some web sites selling these lamps disclaim all responsibility. Also remember WE are made of a LOT of bacteria and viruses. Might not be such a good thing to sterilize your skin daily. Some of that stuff protects you from nastier stuff.

From the article:

> One is that efficacy for formation of CPDs, the main photo-induced DNA lesion which is closely associated with photocarcinogenesis, is highest at approximately 260 nm and decreases at shorter and longer wavelengths, and generation of CPDs at 222 nm is approximately 70% of that at 254 nm, as previously shown in the action spectrum for the formation of CPDs (29). The second is that the 222-nm UVC is too short to penetrate the stratum corneum to reach the basal cell layer, where cancer stem cells are considered to reside (30, 31).

That make sense, and looks like a good explanation. They used 9 mice in each group, but the difference was big enough, so it doesn't look like a problem caused by using a small number of mice. Definitively interesting, but I'd be careful with humans skin (my skin!) anyway until other groups reproduce the result.

UV-B and UV-C are dangerous. As always, the dose makes the poison, so low exposure is safe.

My guess is that they claim is safer for the environment or safer if they broke, but the language is confusing and they seam to claim they are safe in normal use. From https://en.wikipedia.org/wiki/Excimer_lamp

> Mercury lamps are the most common source of UV radiation due to their high efficiency. However, the use of mercury in these lamps poses disposal and environmental problems. On the contrary, excimer lamps based on rare gases are absolutely non-hazardous and excimer lamps containing halogen are more environmentally benign than mercury ones.[citation needed]

> I assume that this is a bad translation and the meaning was that the sterilized food is safe for humans, not the ultraviolet light.

That makes a lot of sense. Usually it's not 100% false, just a bad interpretation. I was not able to imagine the source of the claim, but this makes a lot of sense.