What You Wear Outdoors Can Affect Your Exposure to UV and NIR Light

[Music] today we're going to talk about the effect of clothes on light coming in either blocked by your clothes or what clothes allow to come in and specifically we're going to talk about two types of light today near infrared radiation which you can see right here it's this portion of the spectrum that is just below red in the visible spectrum so you cannot see it it's known as infrared specifically near infrared and we're also going to talk about ultraviolet light as well you should know about these two types of light we've been talking about them

here on medr ultraviolet light is kind of a mixed bag so ultraviolet B helps you make Vitamin D naturally in your skin but unfortunately can also cause some skin damage and things of that nature UVA as well and UVC doesn't get through the atmosphere is also very important in terms of sterilization but we don't have to worry about that in terms of our bodies from the Sun if we look at at the ionizing radiation the damaging radiation from that same Spectrum you can see very clearly that UVA UVB this area right here does the most

damage and so what we Tred to do here is attempt to block as much as possible this type of light generally speaking of course there are some advantages sometimes with getting some of this light it can help with making Vitamin D it can also help with a number of other conditions as well which we're not going to get into but generally people want to try to avoid ultraviolet but notice down here in the near infrared Spectrum the amount of damage that is caused by near infrared is actually pretty low so the question is is there

type of clothing you could wear that would be good at blocking ultraviolet light but allow near infrared light in without an issue this is important because the amount of near infrared radiation that we are getting from the sun over the last 200 years has really been Di diminishing here as you can see in red this was a paper that was written by Zimmerman and Ryder where they looked at the effects of our lifestyle so back in the 1800s we had natural sunlight we went outside we had campfires and then as we got to the 1950s

we still had incandescent bulbs which give off near infrared radiation in abundance and we still had plain glass windows but maybe we didn't go outside as much and so there was a modest decrease by the time we hit 1990 we've got fluorescent bulbs which do not give off near infrared light we've got plain glass windows doing well and we're only spending about 15% outside as opposed to 25% back in the 1950s that takes us to today where we have pretty much all LEDs CFL lights and we have installed in our buildings this type of glass

which filters out near infrared light because near infrared light can heat up buildings and so we don't want that in there from an energy standpoint not necessarily from a health standpoint because it actually may be beneficial to have near infrared light here we can see the spectrum of light bulbs so if we look at a regular incandescent bulb here in blue you can see here that there is plenty of coverage in that near infrared Spectrum whereas we look at a 3,000k LED that you might pick up at the local convenience store or Home Improvement store

and you can see quite clearly that it is limited just to the visible spectrum some people might say that it's very energy efficient and it's not wasting any energy in any area outside of the visible spectrum because you don't want that if you're looking at Energy Efficiency there's a little talk about how that might not actually be beneficial for our health finally let's look at the sun the sun is this yellow uh and you can see it clearly here lots in the visible but the majority of the energy actually coming from the sun is in

the near infrared infrared Spectrum let's talk about those windows that we talked about high medium moderate and low solar low E glass this is going to filter out near infrared what is it that we can do to maximize near infrared light and minimize ultraviolet light so you want to wear clothes but the question is is does it matter what type of clothes you're wearing and has there been any data has there been any studies done on this once again we're looking at near infrared light which can actually penetrate really deep we want that near infrared

light because it has low ionizing energy it actually could be beneficial in the mitochondria of our cells and so you might say well how is that even possible we'll talk a little bit more about that as we get into this the penetration of near infrared radiation deep down into the body but first let's talk about ultraviolet light what's the data on ultraviolet light I actually went to this Healthcare website in Utah at a University from their studies here they're saying that protection from ultraviolet light is going to be best when you have dense fabric particularly

tightly woven or knitted Fabrics that have smaller holes interesting inly dark or bright colors are going to do a better job at reflecting ultraviolet or absorbing it they say here that actually darker colors such as blue or black actually absorb the ultraviolet rays so it doesn't get to your skin then lighter or white Shades and this means that ultraviolet rays are less likely to reach your skin but bright colors like red can also absorb ultraviolet rays and actually the more Vivid the color the greater the protection so if you want to avoid ultraviolet light that

might be something that you might want to look at sometimes they actually even give a UPF rating there are different types of materials we'll talk about this here in a little bit in terms of synthetic materials polyester and nylon are actually more protective than bleach cotton or rayon dry Fabrics offer more protection than wet Fabrics so think about that if you're concerned about ultraviolet lights you want to have a good condition so it doesn't let light in and more fabric of course is better let's talk about near infr red near infrared which is out here

in the Spectrum actually is going to penetrate very deeply because of its longer wavelength in fact as you can see here in this study published by Zimmerman and Ryder it actually penetrated down as deep as 8 cm into the skin it's used practically in hospitals to try to find veins you can see the veins in this picture actually pretty easily I've Got a Friend Robert Fosbury who is an astronomer in Europe worked with the European space agent and NASA here in the United States and he's also very interested in near infrared and its uses for

Earth and life and he sent me this picture of a near infrared Source on the other side of his hand now notice here what you can see it's Illuminating his whole hand there's a lot of light scattering here but notice what you don't see you do not see bones you don't see skeleton and that's because this light is able to penetrate through and Scatter all throughout there's almost like a bioluminescence to this and that's because near infrared light can actually penetrate quite deeply into the human body we're actually almost translucent to near infrared light if

it's strong enough in fact if you were to do the calculations based on the depth this red line right here represents the proportion of all the cells in your body represented by the black line that can actually quote see near infrared light so let's talk about clothes and how clothes might affect this equation here's another picture that Dr Fosbury sent to me this is a regular photograph of his shirt and sweater and as we go to Red Light you can see it a little bit more with near infrared light so this is nir clearly you

can see here that n is penetrating through this fairly easily let's get some data what type of materials does it matter if it's wet or if it's dry and right now I cannot see a better study than this one that was published way back in 2013 they were not really interested in the health benefits of near infrared light they were actually more interested in the usefulness or the leveraging of this penetration for security purposes and so they set up their experiment with a scanning stage the detector was right here the source was here and they

put up these objects and they looked at different layers so let's take a look at the first graph here I think this is really interesting all of these lines are different materials notice here we have a polyester tie we have a cotton vest a cotton SL polyester material denim cotton fleece cotton trousers acrylics denim all these sorts of things and w means that it was wet and if it doesn't have that it means it was dry there's two groups there's this group here and there's this group over here this is the number of layers one

two layers three layers four layers this is actually getting to the point here where you probably would never put like 13 layers on what you can see here very clearly is that the cotton polyester and the just the overall polyester in black and maybe if we wanted to add into that the wet cotton vest seem to do the best at allowing the near infrared through its material these ones in this group would be good but notice even if you're just wearing one or two layers the amount of transmittance through that layer is still a good

80% it's as if you weren't even wearing the clothes at all what are the things that are going to prevent near infrared transmission it's the group right over here and obviously the biggest Defender here is denim so denim jeans one layer though of denim jeans you can see here drops it down to about 50% even though denim seems to be the one that blocks it the most we rarely wear more than one layer of denim and even if we were to do that it's only dropping it here by 50% it's not like it's not even

going through so I think the point of this screen here is that number one you've got to use many many many layers to attempt to block out near INF red light the bottom line here is that n infrared light can penetrate very well but you can also see here that there are some materials that are better suited for allowing that near infrared to penetrate here's cotton towels also very similar to denims as well so some people have asked whether or not the color matters so we saw that the color May matter for ultraviolet does the

color really matter for near infrared light let's take a look and as it turns out not as much as you might think and you can see here white red yellow green number two white poly which is white of course black blue white number two blue and poly which is black notice here blue generally speaking up here is going to allow near infrared through the color green seems to not allow near infrared through as much and in fact tends to reflect and there's something about the color green because we also notice this in nature that green

leaves green grass Gass is very reflective of near infrared light which is great if you're not covered with it you want to allow that near infrared in so you're going to want to pick colors up here in this area so whites Blues but overall does it really matter no if you're wearing one or two layers the difference spay there is really really small and here's a picture of what I was talking about this is a picture of a tree with green leaves notice how reflectant they are they're bright white and they are reflecting that near

infrared light here's also another figure from that study and you can see they have this shirt which is the area that they are studying and behind it they have something that somebody might want to get past security some cell containing granules or some sort of a material that they contain either powders or liquids and what they could see is if you look at this here they could with near infrared make out the image of this thing behind the screen so it actually worked They concluded that the ability of n energy at 850 NM which is

in the near infrared Spectrum was the paracity of the Fabrics how porous was it and the spatial distribution of the pores so I will give you another look here at the slide so you can study it the take-home message here is if you're generally going out with one or two layers where you want to look is right here and right here and if you want to get the most amount of n infrared possible you probably want to avoid denim at this point here and go more along with some of these materials so long as you

can keep warm so the question often comes up is when should somebody go outside and I want to show you this slide again this is from Russell Ryder and Scott Zimmerman who did a really good job if you're looking at near infrared photons because near infrared photons can penetrate through the atmosphere at any angle the amount of n photons hitting your body are going to be in inversely proportional to the amount of atmosphere between you and the Sun and so that Sunrise you're going to get a small amount but as the day goes on you're

going to get larger and larger amounts just based on the geometrical distribution of the Sun in the sky as it goes from sunrise to sunset on the other hand ultraviolet which we talked about as the damaging rays but remember also it makes vitamin D because it is not able to penetrate the atmosphere very cleanly because it can't get through very easily there's going to be a dir of ultraviolet light hitting in the early morning hours and also in the late evening so this might be the time where you want to get a relatively increased distribution

of near infrared but a relatively small ultraviolet distribution so going outside in the morning going outside in the late evening when the Sun is up so I hope that this has been helpful we're going to put a link in the description below don't forget to subscribe turn on notifications tell your friends about medr and if you have continuing medical education needs please visit us at medcram.com thanks for joining [Music] us