(This is the second of two columns about sun exposure.)

Ultraviolet (UV) rays, an invisible component of sunlight, can cause skin damage, cataracts, wrinkles, age spots, and skin cancer. These rays also impair the skin's immune system.

UV rays can hurt you on cloudy as well as sunny days. UV rays also bounce off surfaces of the ocean, sand, snow and cement.

One of the surest ways to reduce your exposure to UV rays is to stay out of the sun when it is the strongest. Those times in North America are between 10 a.m. and 4 p.m. in the late spring and early summer.

Other ways to protect yourself are to wear protective clothing, such as a wide-brimmed hat, long-sleeved shirt, and long pants. You should use a sunscreen rated at SPF 15 or more.

Eye doctors recommend wraparound sunglasses that provide 100 percent UV ray protection.

You should also pay attention to the UV Index developed by the National Weather Service and the Environmental Protection Agency. This index assesses risk of overexposure to UV rays.

The UV Index is calculated daily and is reported by the press. It can be found at: http://www.epa.gov/sunwise/uvindex.html [1], where you can plug in your own Zip code to find out the index rating in your area.

The following are the index levels:

2 or less: Low danger for the average person

3 to 5: Moderate risk of harm

6 to 7: High risk of harm.

8 to 10: Very high risk of harm.

11+: Extreme risk of harm.

It is possible to go outside when the UV Index is 11 or higher but you must be sure to take every step possible to protect yourself sunscreen, hats, long sleeves, sunglasses, the works.

Not everyone reacts to the sun in the same way. The level of danger calculated for the basic categories of the UV Index are for a person with Type II skin. The following are the skin types:

I Always burns, never tans, sensitive to sun exposure

II Burns easily, tans minimally

III Burns moderately, tans gradually to light brown

IV Burns minimally, always tans well to moderately brown

V Rarely burns, tans profusely to dark

VI Never burns, deeply pigmented, least sensitive

What is a suntan?

When UV rays penetrate the skin's inner layer they generate the production of melanin a dark pigment. The melanin eventually moves toward the outer layers of the skin and becomes visible as a tan. Every time you tan, you damage your skin and this damage accumulates over time.

There is no safe tan. What some call a base tan may, actually, increase the chances you'll get a burn, because you're likely to stay out longer without properly protecting your skin.

You should stay away from tanning beds and sunlamps because they emit UV rays that can cause serious long-term skin damage. The amount of the radiation produced during indoor tanning is similar to the sun's production and in some cases may be greater.

Many tanning salons are unregulated. They allow customers access to tanning beds without supervision or eye protection.

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