Understanding UV Rays and Skin Damage

The sun emits radiation along the entire visible as well as ultraviolet spectrum range. In addition, the sun also emits infrared radiation, and even radio waves!

Thankfully, we only need to protect ourselves from ultraviolet radiation. As you probably know, ultraviolet (UV) rays reach your skin causing sunburn and even DNA damage. This results in cellular mutations that can lead to skin cancer. The most deadly form of skin cancer is melanoma.

This post will dive deeper and examine which specific types of UV rays actually harm your skin. After reading this, you will be better educated when selecting sun protection.

First, let’s view the entire electromagnetic spectrum below.

electromagneticspectrum.jpg
Source: Stanford Solar Center

You’ll notice that the UV spectrum is located just to the left of the “visible” spectrum. Humans can see the visible spectrum, whose various wavelengths account for the different colors, but the UV spectrum, composed of wavelengths between 10 and 400 nm, cannot be seen by the naked eye.

Its a wonder that such a small sliver of the entire electromagnetic spectrum causes such massive damage to our cells.

Different types of UV radiation

Spanning from 10nm – 400nm, UV radiation imposes various types of damage to our skin based on the wavelength, frequency, and energy.

In general, shorter wavelength UV rays cause the most damage. This is because shorter wavelengths have higher frequency and a higher amount of energy. Higher energy radiation elicits more harm because it penetrates deeper into skin, tissues, and cells.

Scientists categorize UV radiation into three bands corresponding to the different wavelengths: UV-A, UV-B, and UV-C:

UVC (10-290nm) – completely absorbed by Earth’s atmosphere
UVB (290-320 nm) – 90% absorbed by Earth’s atmosphere
UVA (320-400 nm) – not absorbed by Earth’s atmosphere

Each of the UV bands present different types of risks for humans

As radiation is emitted by the sun towards Earth, the atmosphere (composed of nitrogen, oxygen, carbon dioxide, argon, etc) helps to absorb a large amount of the UV radiation.

Remember how we said the shorter wavelengths of light are more harmful? The good news is that most these shorter wavelengths of radiation (UVB and UVC) are blocked ozone, water vapor, oxygen, and carbon dioxide in the atmosphere.

Specifically, all UVC radiation, and 90% of UVB radiation is absorbed. These rays are largely blocked by our atmosphere because of the unique way that they interact with those chemicals in our atmosphere. Much like sunscreen contains chemicals to absorb certain bands of UV rays, our atmosphere is our best friend for UV protection.

Unfortunately, our atmosphere can only protect so much.

Longer wavelength UVA radiation, for example, is less affected by the atmosphere, so a large amount of the UVA band makes it through. Even though only about 10% of UVB radiation makes it through to pose a risk to humans, a large amount of UVA makes up the dangerous solar radiation that we are exposed to when we go outside on a sunny day.

Once the rays get to our skin, UVA radiation (which lower energy than UVB radiation) tends to penetrate about two layers of skin, causing sunburn and wrinkles long term. The good news, however, is that UVA radiation’s longer wavelength and thus lower energy means it cannot penetrate through our cells, so it does minimal to no DNA damage.

UVB rays, on the other hand, have a slightly shorter wavelength as well as a higher frequency and energy than UVA rays. UVB rays do penetrate our cells and damage DNA causing mutations and skin cancer.

How about UVC rays?

Well – UVC rays have previously been found in tanning beds, and because of the shorter wavelength, higher frequency, and thus greater energy, these rays are extremely damaging, if you are by chance exposed to them. Thankfully, you don’t have to worry about sunlight containing UVC since the atmosphere blocks them completely.

Conclusion:

To protect yourself from wrinkles, block UVA rays.

To protect yourself from DNA damage / cancer, block UVB rays.

UVC rays are largely used in some types of artificial light used for disinfection, such as those made by the company Klaren. Aside from that, there is little risk that UVC rays from the sun will be of any worry.

Sources:

https://www.ncbi.nlm.nih.gov/pubmed/20806994

https://www.who.int/uv/uv_and_health/en/

https://www.skincancer.org/prevention/uva-and-uvb

https://share.upmc.com/2014/07/infographic-abcs-uv-difference-uva-uvb-uvc/

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