# UV light dangerous to skin?



## Pointoflight (Sep 29, 2014)

Calling upon the collective knowledge of the geniuses that reside here to help me answer the following question: I work in a field where I am exposed to urine alot (I work in a kennel and vet's office and get urinated on alot by dogs and cats). Though I wash often, I was thinking about using a UV LED light pen (375nm) to check the skin on my arms, legs, and clothing for any possible dried urine that I may have missed. Does anyone know if exposure to UV light at 375nm 10 times a day for about 1-2 minutes is harmful? I've tried to research this and get conflicting answers mostly from people who don't have any knowledge of light. Would appreciate it if someone with extensive experience working with UV lights would share their thoughts on this question. 

Thank you gentlemen in advance for your thoughts on this subject. 

Respectfully, 
Nicolas.


----------



## CoveAxe (Sep 29, 2014)

That particular wavelength falls under UVA (Ultraviolet light that is not absorbed by the ozone). This is the UV that gets you tan when you sunbathe.

You are getting much more exposure to UVA from walking outside at noon for a few seconds than you are from a UV pen light for a few minutes.

I really wouldn't worry about.


----------



## Pointoflight (Sep 29, 2014)

CoveAxe said:


> That particular wavelength falls under UVA (Ultraviolet light that is not absorbed by the ozone). This is the UV that gets you tan when you sunbathe.
> 
> You are getting much more exposure to UVA from walking outside at noon for a few seconds than you are from a UV pen light for a few minutes.
> 
> I really wouldn't worry about.



Thanks for the response. In reading my post, I don't think I was clear enough about the exposure, so to be more specific, exposure would be 1-2 minutes about 10x a day for a total of 10-20 minutes of exposure per day with the uv light pen at 375nm. The light pen has 3 UV LEDs. Does that change anything in your opinion? 

Thanks again, Nick.


----------



## TEEJ (Sep 29, 2014)

Pointoflight said:


> Thanks for the response. In reading my post, I don't think I was clear enough about the exposure, so to be more specific, exposure would be 1-2 minutes about 10x a day for a total of 10-20 minutes of exposure per day with the uv light pen at 375nm. The light pen has 3 UV LEDs. Does that change anything in your opinion?
> 
> Thanks again, Nick.



What is the exposure in watts/cm2 or mJ/cm2 of skin?

My GUESS is, that if its a PEN light, its a teeny weeny exposure.

Its not just the wavelength, its the intensity that matters.



Have you considered a barrier cream/PPE to keep the urine off your skin better?


Pasted from ACGIH:

There are no regulatory UV radiation exposure limits. The American Conference of Governmental Industrial Hygienists (ACGIH) publishes Threshold Limit Values 
(TLVs), which are recommended exposure limits. The UV radiation exposure limits are wavelength dependent, ranging from 3 mJ/cm2 to 100,000 mJ/cm2. 

For UV-A (315 nm to 400 nm), the ACGIH recommends 1.0 J/cm2 for periods lasting less than 1000 seconds, and 1.0 mW/cm2 for periods lasting greater than 
1000 seconds.


----------



## Pointoflight (Sep 29, 2014)

Pointoflight said:


> Thanks for the response. In reading my post, I don't think I was clear enough about the exposure, so to be more specific, exposure would be 1-2 minutes about 10x a day for a total of 10-20 minutes of exposure per day with the uv light pen at 375nm. The light pen has 3 UV LEDs. Does that change anything in your opinion?
> 
> Thanks again, Nick.



Again, thanks for the response. Found this university article. Didn't make me feel too good about using the blacklight pen on my skin to detect remaining urine. Still not sure what this all means since the article said at one point that exposure to UVA light for up to 8 hours is safe and then said not good to shine on your skin for 10 seconds? 

Here's the linke to the article if anyone wants to see it. 


https://www.case.edu/ehs/Training/UV/UVsafety.pdf


----------



## Pointoflight (Sep 29, 2014)

TEEJ said:


> What is the exposure in watts/cm2 of skin?
> 
> My GUESS is, that if its a PEN light, its a teeny weeny exposure.
> 
> ...



I don't know the intensity of the penlight in terms of watts/cm2. I assume as well that if it's a penlight it's not very intensity, but don't know if intensity how much intensity plays a role in terms of damage to the skin? Obviously if very intense it logically would cause more damage, but would even a low intensity cause skin damage. The article was kinda scary. Really wanted to do this on a regular basis, but now, not too sure. As far as the barrier to the skin, thanks for the suggestion. The urine doesn't really damage my skin, just wanted a way to check to see if I was getting it off when I was washing up. It goes everywhere. 

Thanks for the reply.


----------



## CoveAxe (Sep 29, 2014)

Pointoflight said:


> Thanks for the response. In reading my post, I don't think I was clear enough about the exposure, so to be more specific, exposure would be 1-2 minutes about 10x a day for a total of 10-20 minutes of exposure per day with the uv light pen at 375nm. The light pen has 3 UV LEDs. Does that change anything in your opinion?
> 
> Thanks again, Nick.



Your pen light is going to have a UV flux on your skin that is miniscule compared to what you get from the sun. We're talking on the order of tens of microwatts/cm^2. Unless the pen light is pressed right up against your skin in the same spot or in your eye for 20 minutes a day, I wouldn't worry about it. You are getting far more exposure from the sun.


----------



## caseyse (Oct 3, 2014)

Pointoflight said:


> Does anyone know if exposure to UV light at 375nm 10 times a day for about 1-2 minutes is harmful? I've tried to research this and get conflicting answers mostly from people who don't have any knowledge of light.



I needed to erase a couple EPROM chips several years ago and the only UV light I had was used in my drinking water filtration system. The UV light was about 260nm to disinfect. So I pulled the light out of its carrier and placed the EPROM chips inches away from the light. It worked well to erase the chips, but an accidental exposure of my hand of no more than a second gave me a skin burn. 

I was surprised at the strength of that little 6W UV bulb.


----------



## PhotonWrangler (Oct 4, 2014)

We are awash in longwave UV all day long from the sun as well as from fluorescent lamps. A longwave UV penlight's output is a tiny drop in a large bucket by comparison. I wouldn't worry about it.

That UVC germicidal bulb is another story though. That 260nm wavelength can do nasty things.


----------



## CyclingSalmon14 (Oct 5, 2014)

I was going to ask a similar thing but it looks in regards to skin its fine.

So its all about the wave length by the looks of it then!

What about say a 3W P60 such as

http://www.kaidomain.com/product/details.S022214

Would I need to worry about that? I am not to botherd, if I start tanning then I'll stop using it ahaha, but I don't plant on pointing it at my self much mainly for GITD and to play with a new wave length.

Could I theroerticly speaking get a tan with this power / wavelength? (I don't plan on trying as I like not haveing cancer...I think sunbeds ect should be banned!)

I AM CONCERNED about eye damage, do I need to take any preventive measures at these wave lengths and powers, I'm not going to be shineing it in my face though...

Why dose lower wavelenths chase much more dmagae much quicker at same power?


----------



## Esko (Oct 5, 2014)

Roughly 1/10th of the sunlight is UV (mostly UVA). It means roughly 100W/square meter or 10mW/cm^2 in summer sun. 



CyclingSalmon14 said:


> Could I theroerticly speaking get a tan with this power / wavelength? (I don't plan on trying as I like not haveing cancer...I think sunbeds ect should be banned!)



Theoretically, yes, I believe you could get local tan. However, sunlight does contain some UVB also, so, even at the same power levels (per cm^2), it makes you tan faster. 



CyclingSalmon14 said:


> I AM CONCERNED about eye damage, do I need to take any preventive measures at these wave lengths and powers, I'm not going to be shineing it in my face though...



The problem with eyes is that your pupils react on visible light and if it is all UV, your pupils will be wide open. However, if you are not shining it to your eyes (constantly/for longer periods) or looking at the led directly, I wouldn't be too concerned.



CyclingSalmon14 said:


> Why dose lower wavelenths chase much more dmagae much quicker at same power?



The lower the wavelengths, the more powerful the photons. UV can cause changes on molecular level and UVC is already powerful enough to break bonds in DNA.


----------



## PhotonWrangler (Oct 5, 2014)

Esko said:


> UV can cause changes on molecular level and UVC is already powerful enough to break bonds in DNA.



Yes! That is how it kills germs.


----------



## CyclingSalmon14 (Oct 5, 2014)

Thank you, very informative!I always wondered how light killed germ's, now I know! I have a movie theory now, girl goes to suntan bed, come out as a mutant golden brown monster.......Ok ill get my hat, the next spielberg i am not ahah.


----------

