Tag: sun protection

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/

Chemistry of Sunscreen

Stop by a Wallgreens or CVS and you’ll notice a large sunscreen selection, but each product has advantages and flaws. The differences, it turns out, depend on the chemistry of each active ingredient. If you’re in the United States, glancing at the list on the back of each bottle, you’ll see that products tend to have some combination of 8 common active ingredients.

But did you know that of the 8 most common active ingredients, there are actually only two different UV protection mechanisms? Categorized below, you’ll notice that UV filter compounds are much more common, while the mineral blocker type only include two of the main compounds.

Sunscreen lotion contains active ingredients that contribute to the sunscreen’s SPF, protecting you from sunburn by keeping UV rays from reaching your skin and damaging cells. Active ingredients protect you from UV rays in two unique ways:

Filtering:

This method filters or absorbs UV light, turning the radiation into heat energy, rather than allowing it to cause cell damage.

UV filters chemical ingredients: Avobenzone, Homosalate, Octisalate, Octocrylene, Oxybenzone

  • Hazards of UV filters:
    • UV filters can and have been measured in blood of people who use sunscreen frequently. The main concern with these chemicals is endocrine disruption.
    • Oxybenzone is by far the most dangerous chemical found in sunscreen. It penetrates the skin easily and enters the blood stream. It has the ability to penetrate the blood-brain barrier, causing hormone disruption. It is estrogenically active and has potent anti-androgenic effects.

Blocking:

Blocks UV light from penetrating through the mineral ingredients in the sunscreen so that it never comes into contact with your skin. (ex. Zinc Oxide and Titanium Dioxide)

Pick up your tube of sunscreen and look at the back. You’ll see a number of active ingredients. Typically, you’ll see 4 or 5 Filtering type ingredients listed. The compounds that protect by Filtering will tend to absorb only certain wavelengths of light, so sunscreen companies include a combination of different ones to block a broader spectrum of UV rays.

Blocking type ingredients work in a different way, so they are present either by themselves or with a few filter ingredients. For example, you might have sunscreen that lists zinc oxide as the only active ingredient.

To avoid sunburn and more importantly skin damage from UV rays, elect for a broad-spectrum sunscreen with as high an SPF as possible, and ideally use a sunscreen that also contains Zinc Oxide or Titanium Dioxide.

UV blocking minerals: Zinc Oxide, Titanium dioxide

  • Hazards of mineral blockers:
    • Zinc Oxide and Titanium dioxide particles are photoactive, meaning they can create free radicals when exposed to UV radiation that damage surrounding cells. To mitigate this risk, manufacturers apply surface coatings to these particles.
    • Both of these mineral blockers are electrically charged molecules. Over time and due to heat exposure, these mineral blockers can settle or clump, leaving gaps in skin coverage. To be effective, mineral sunscreens contain ingredients that hold zinc oxide or titanium dioxide in a suspension to provide an even coating on the skin.
    • Titanium Dioxide creates more free radicals that do oxidative damage to your body and skin cells, and increases aging processes. Zinc oxide tends to have a broader-spectrum range of coverage than titanium dioxide, although the combination of both Zinc Oxide and Titanium Dioxide provide the broadest range of protection.
    • Zinc and titanium oxide may potentially harm environment.

Some products, such as “SheerZinc Face” by Neutrogena, will contain zinc oxide. Finding a product that contains both zinc oxide AND titanium dioxide is much less common due to the highly charged particles tendency to coagulate and cause clumping.

Conclusion:

As discussed, there are two different types of sunscreen. If you are going for a product that contains Mineral Blockers, Zinc Oxide is preferred over Titanium Dioxide. Check products that contain mineral blockers to ensure lotion consistency is homogenous and not de-coagulated because the clumps will cause gaps in skin coverage, thus causing you to get burnt.

Your ideal sunscreen might have the following active ingredients:

  • Homosalate (8–10%)
  • Ocinoxate (variable percentage)
  • Octocrylene (2–6%)
  • Zinc Oxide (5–15% +)