Pale people of the world, beware of the shining, warm sunlight! UV radiation, with a shorter wavelength than visible light, is absorbed by skin causing a sunburn and long-term skin damage. The Earth's atmosphere filters the majority of UV rays before they reach pasty humans; however, UV rays still penetrate the atmosphere. Exposure to UV radiation changes based upon altitude, distance from the equator, time of day, season and amount of cloud cover. At noon, with the sun high in the sky, sunscreen is heavily advised. How does sunscreen protect people from UV radiation?
Sunscreen includes organic and inorganic compounds to reflect, scatter, absorb and release UV rays. Inorganic ingredients such as titanium dioxide and zinc oxide form a physical barrier between UV rays and skin. Because of this barrier, less rays penetrate deep layers of skin. Organic ingredients absorb UV rays and release them as heat.
There are two different types of UV rays. UVA rays penetrate multiple layers of skin and cause long-term skin damage. UVB rays cause the visible sunburn and effect top layers of skin. Both types of UV radiation are bad. The SPF of a sunscreen is the measured UVB protection of the formula; there is no standard for UVA protection. A broad spectrum sunscreen protects against both types of rays. A sunscreen with a SPF of 15 means that one could spend 15 times as long in the sun before getting burned compared to the time necessary to get burned without sunscreen.
Why wear sunscreen? Well, besides the fact that prolonged exposure to UV rays can lead to skin cancer and eye damage, UV radiation also can reduce the effectiveness of one's immune system. This fact seems strange. But, since UV rays displace or kill some cells necessary to trigger immune system responses, the body's ability to fight infections decreases.
So, as we all await the end of school and the sunny days of summer, remember the importance of applying sunscreen!