Imagine this: Your last exam is written; school's out for summer...It's time head to the beach! You pack your swimsuit and towel; the car is loaded with friends as all of you prepare to head out to the golden sand and into the glorious sunshine. But wait...just as you are running out of the house, you hear that voice saying, "Don't forget your sunscreen!"

Nothing tops the feeling of being outside on a beautiful day. The sun's rays can magically elevate your spirit and relax the soul. But here's the kicker: those rays can also cause damage to your skin.

Sunlight, the stuff that is beamed down from the big yellow circle in the sky, is composed of infrared (IR), visible and ultraviolet (UV) light. Visible and IR light pose little threat to our skin since they are longer wavelength and lower in energy than UV light. On the other hand, UV rays are the highest energy components of natural sunlight and have the potential to do the most damage to our skin.

 

Did you know? Ultraviolet light is higher in energy than infrared light. Having more energy, UV rays can penetrate into the skin and cause more damage than low-energy IR rays.

The interaction of UV light with your skin cells is a complex process that can produce a variety of effects, most notably tanning, sunburns, premature skin aging, and skin cancer. Tanning is the skin's natural response to UV exposure and is the result of increased production of the skin pigment (i.e., melanin), which gives skin a golden brown colour. However, the latter, more negative effects (i.e., sunburns, premature skin aging, and skin cancer) are all caused by the photochemical degradation of key biological molecules like amino acids, collagen, DNA, and RNA.

 

Did you know? UV rays in sunlight are responsible for the photochemical degradation amino acids, DNA, and RNA in the skin, which leads to skin damage such as sunburns, aging and cancer.

With all the potential issues arising from over exposure to UV light, how can the problems be overcome? The most logical, but probably least practical and certainly the most boring solution is avoiding the sun altogether.

Rather than spending all day in a dark room, a more preferable solution is to squirt a big ol' glob of sunscreen on your hand and apply it to all of the exposed, and even unexposed, skin you can find.

Sunscreens prevent harmful UV light from penetrating into your skin through simple, yet unique, molecular properties associated with their active ingredients; these active ingredients are often referred to as physical and chemical UV blockers.

 

Did you know? The active ingredient in sunscreen can be classified as a physical or chemical blocker.

Physical blockers are the simplest type of sunscreens, and are typically composed of inorganic oxides, such as zinc oxide (ZnO) and titanium dioxide (TiO2). These blockers rely on their physical properties to block UV light. Particles of physical blockers have very high refractive indexes, which is a material's ability to change the direction of light as it passes from one medium to another. Therefore, physical blockers do just as they describe: they physically block, or more specifically reflect and scatter UV light away from the skin...kinda like a ball hitting a wall and bouncing off in a different direction.

 

Did you know?
Physical blockers have a high refractive index. This means that they are very good at reflecting incoming UV rays away from the skin.

Chemical blockers, such as the para-aminobenzoic acid (PABA) family, are typically organic molecules. They act in a more complicated manner than physical blockers. With a molecular structure that is specifically designed to absorb UV light, chemical blockers can "grab" the UV rays before they penetrate into the skin cells. UV light that is absorbed by a chemical blocker is converted to a longer wavelength/lower energy form (IR light) which is harmlessly radiated away from the skin, thereby decreasing potential negative effects posed by UV light. Contrary to their name, chemical blockers retain their molecular structure during their dance with UV rays (i.e., no chemical reaction takes place); so the term "chemical blocker" is actually a misnomer; it is the physical properties of chemical blockers that let them work their magic.

 

Did you know?
Chemical blockers are organic molecules that are designed to absorb UV light and convert the light to the harmless low-energy IR light.

So, next time you are running out of the house, surfboard and beach towel in hand, ask yourself, do you feel physical or do you feel chemical, and grab the sunscreen that best suits your mood

For further investigation:

www.cancer.ca

References

"Physician's Guide to Sunscreens" 1991, Marcel Dekker, INC. New York. Editor: Nicholas J. Lowe.

"Sun Damage and Protection" http://www.telemedicine.org/sundam/sundam2.4.1.html

Jeff Landry grew up on the beaches of Lake Erie in Wainfleet, ON, often waging battles with the dreaded UV rays during endless summer days of scampering around the lake. After realizing sunburns don't pay, he headed off to McMaster University, getting a BSc in Chemistry. Following the call of science, Jeff moved eastward to Halifax, and is currently enroute to a PhD at Dalhousie University in the area of non-carbon based polymers. When not in the lab Jeff can be found ripping up the local trails on his mountain bike, trying to keep the rubber side down.

CurioCity

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