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UV Rays: The science behind sunburns

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By Gina Ressler
Meteorologist
@ginaressler
Wednesday, June 4, 2014, 8:29 AM

Getting outside in the summer is one of the best things we can do for our mental health.


PROTECT YOURSELF: Cases of skin cancer in Canada on the rise


But spending long hours in the sunshine is not without its risks. Just look at the stats: According to the Canadian Cancer Society, skin cancer is one of the fastest-rising cancers in the country

The number one risk factor for developing skin cancer is exposure to UV radiation – and it’s entirely preventable.

UV Radiation

UV stands for “ultraviolet”. Ultraviolet rays are just like rays of light, except we can’t see them. Both UV rays and visible light are types of electromagnetic radiation emitted by the sun. Electromagnetic radiation is a form of energy that behaves like a wave and travels through space at the speed of light. We measure the energy of electromagnetic radiation by its wavelength. The shorter the wavelength, the higher the energy.

Different wavelengths of radiation have different names, and I bet you've heard of some of them before: Gamma Rays, X-Rays, Ultraviolet Rays, Visible Light, Infrared, Microwave, Radio Waves.


Image credit: NASA / Goddard Space Flight Center


Most of the sun’s radiation is emitted in the form of visible light. (No, that’s not a coincidence! Human eyes evolved to detect the visible part of the spectrum the best.) But there’s a significant portion solar radiation emitted as infrared, and a small amount as ultraviolet as well.


Image credit: University of Tennessee at Knoxville


Infrared (IR) radiation has longer wavelengths than visible light, and does not pose any danger to our skin. Ultraviolet (UV) radiation, on the other hand, has shorter wavelengths than visible light, and as a result, can damage our skin.

There are three types of UV rays, ranging from the longest wavelength to shortest: UVA, UVB, and UVC.

UVA Rays

  • UVA rays have the longest wavelength out of the three.
  • Although they’re weaker than UVB and UVC rays, they can penetrate deeper into the skin. UVA rays penetrate into the dermis, damaging the elastin and collagen fibres, resulting in premature skin aging and wrinkles.
  • Tanning beds commonly emit UVA rays, since they don’t burn the skin readily. UVA rays result in a more immediate tan, but they fade quickly.
  • The ozone layer doesn’t readily absorb UVA rays, so about 95% of them pass through.
  • UVA rays can penetrate clouds and glass.

UVB Rays

  • UVB rays are shorter and stronger than UVA rays.
  • UVB rays penetrate into the first layer of the skin, the epidermis, and they’re responsible for redness and burning, and related to most forms of skin cancer.
  • Unlike UVA rays, UVB rays result in a delayed tan that appears 48 to 72 hours after exposure.
  • The ozone layer absorbs the majority of UVB rays.
  • UVB rays do not penetrate glass significantly.

UVC Rays

  • UVC rays are the shortest and strongest rays, and can be harmful to the skin and eyes.
  • Thankfully, virtually all UVC rays are absorbed by ozone and other atmospheric gases before reaching the Earth’s surface.

Image credit: web site


All types of UV rays increase the risk of skin cancer.

Any type of UV exposure can be harmful, whether from the sun or from tanning beds. Each time your skin becomes tanned or burned, your skin cells and DNA are damaged. Although your skin can heal from a sunburn, the underlying damage remains.

Do yourself and your family a favour, and make sun protection a priority.

UV Index

The UV Index is a measure of the maximum intensity of the sun’s UV radiation on a given day. The Index ranges from low (0) to extreme (11+), and can help you take the necessary precautions. The forecast UV Index takes into account location, altitude, time of year, cloud cover, and stratospheric ozone concentration.

The higher the UV index, the greater the need to protect yourself. Don’t confuse temperature with UV rays. It doesn’t need to be hot for UV rays to burn you!

Before going outside, check the UV index and protect yourself and your family.

Thumbnail photo courtesy: FLICKR- Sara Lynn Paige

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