A little something about UV safety and health

Gather round, the UV-guru is here.

To preface this: if you have any suspicion that you got hurt by a UV source, ALWAYS seek medical care, ASAP. Don’t look for answers here, just go.

I’ve been seeing a lot of questions about UV and its effects on health. There’s some conflicting info so I’ll try to summarize everything here, feel free to correct/add things.

UV (Ultraviolet) is a region of light spectrum whose wavelength is shorter than that of visible light (blue and violet part) but longer than X-rays. UV is generally divided into 3 groups:

* UV-A: 315-400nm
* UV-B: 280-315nm
* UV-C: 100-280nm

There are more groups such as UV-vacuum with even shorter wavelength but these are not encountered unless you’re in a physics lab so I’ll omit them.

It is important to note that the energy of photons increases as the wavelength shortens. Therefore, the closer to zero you are in nm, the higher the ability of the photon to induce chemical reactions.

* At Earth’s surface, we mostly encounter UV-A which is able to penetrate Earth’s atmosphere all the way down. The energy of these photons is still insufficient to cause significant chemical reactions and that’s why it’s the least harmful. However, it can still cause indirect damage, such as depleting Vitamin A and producing reactive chemical species, so caution still needs to be taken.
* UV-B is where things are getting really dangerous. With higher energy, these can penetrate the dead skin layer and cause double-strand breaks in DNA in your skin. In better cases, the only consequence is a sunburn, in worse it’s cancer. Fortunately, most of UV-B gets absorbed by the ozone layer and only a very small percentage actually makes it to surface.
* UV-C possesses the highest energy per photon and is classified as [ionizing radiation.](https://en.wikipedia.org/wiki/Ionizing_radiation)It gets completely absorbed by the atmosphere and the only sources of UV-C are artificial. The logical assumption would be, that it causes even more dangerous effects than UV-B. However, the wavelength is so short that it cannot penetrate skin deep enough (mostly) and gets absorbed by our dead skin cells on the surface, basically cooking them. It is painless (for some time) and smells like fried bacon. Ask me how I know. UV-C is the one most commonly used to sterilize surfaces, as it very effectively kills everything that it can reach. Note that the layer of dead skin is not uniform, so the risk of DNA damage is still there.

In short: UV-A is not great, not terrible; UV-B is cancer ray; and UV-C is Life-obliterator 5000.

Now that we established a baseline for each one, let’s move to the fun stuff: eyes.

Eyes are an extremely sensitive organ. Unlike the rest of the body there’s no layer of dead cells to shield it from harm. That purpose is fulfilled by the eyelids. But even the blinking reflex can be too slow with lower wavelengths or higher intensity light.

The golden rules:

* Wear eye protection at **all times**
* **Never** shine a UV source straight into your eyes. Avoid skin as much as possible.
* **Always** be aware of your surroundings (people/animals)

Basically, just behave like you’re holding a gun. The responsibility yours. Now, how can you protect your eyes from these naughty photons?

* For UV-A, most prescription glasses already have a filter that blocks UV-A (but check to be sure). Otherwise, wear goggles made from UV-A-absorbing plastic, such as [polycarbonate](https://en.wikipedia.org/wiki/Polycarbonate).
* For UV-B, investing into some [quality goggles](https://www.survivallaser.com/Safety_Goggles/cat556089_826120.aspx) specifically designed for UV-B is a good idea. Trust me, your eyesight is much more valuable than cheapo fake UV goggles from amazon.
* As for UV-C… just don’t play with it. It has no inherent advantages over the previous 2 in terms of goofing around and is legitimately dangerous for you and everyone around you. Also, unless the UV-C is produced by quartz mercury bulbs, you’ll [pay dearly](https://www.futureelectronics.com/de/p/semiconductors–Led-lighting-components–led-lighting–ultraviolet-lighting-leds–uv-leds/ncsu434a-nichia-9135569) for the LEDs. Just leave it alone.

This begs a question: what if you’re a dumbass and forgot to wear goggles, what is the damage? Contrary to popular belief, UV damage your retina is not as severe, as it usually can’t penetrate that deep. That honor would go to infrared, where your eye is fine until you hear a pop and suddenly you can’t see (added drama but the point stands). The UV damage is very focused on cornea and lens, as these strongly absorb UV photons.

* UV-A overexposure causes irritation, tears and discomfort. I would compare it to having really tired eyes after a long day. With a little rest, it’ll pass
* UV-B can cause what’s known as “snow blindness”, medically known as photokeratitis, which can have lasting effects. Good comparison is someone throwing sand in your eyes that you can’t get out.
* UV-C is the most severe, as the damage is very concentrated on your cornea. It’s known as “welder’s flash”, a more serious version of photokeratitis. If the exposure was significant, it can lead to permanent eye damage and vision loss. The pain is like if someone was pushing you face-first through Sahara sand dunes scorched by midday sun. (I wasn’t kidding when I said don’t screw around with UV-C)

Some things here are simplified for brevity’s sake. If you’d like to know some more about some specific aspect of UV, just drop me a message or comment here, I’d love to have some feedback.

On a final note, I’d like to say that I consider UV flashlights a lot of fun to play around with and I’m not discouraging anyone to get one. Just keep in mind the precautions you need to take and always put safety first.

Happy fluorescing!

by Bioforest