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UV RADIATION

Any time the sun's ultraviolet (UV) rays are able to reach the earth there is a risk for excessive sun exposure. The ultraviolet (UV) portion of sunlight is an invisible form of radiation that can penetrate and change the structure of skin cells.

Exposure to UV rays appears to be the most important environmental factor in the development of skin cancer and has also been associated with various forms of eye damage, such as cataracts.

There are three types of UV rays: ultraviolet A (UVA), ultraviolet B (UVB), and ultraviolet C (UVC).

UVA is the most abundant source of solar radiation at the earth's surface, and penetrates beyond the top layer of human skin. Scientists now believe that UVA radiation can cause damage to connective tissue and increase a person's risk of developing skin cancer.

UVB is less abundant at the earth's surface than UVA because a significant portion of UVB is absorbed by the ozone layer. UVB does not penetrate as deep into the skin as UVA does, but, nonetheless, can also be damaging and has been associated with the development of skin cancer.

UVC radiation is extremely hazardous to skin, but it is completely absorbed by the stratospheric ozone layer and does not reach the surface of the earth.

UV OUTLOOK INDEX

The Weather Channel has developed a current and forecast ultraviolet (UV) index to help you prevent overexposure to the sun's rays. The following risk categories are used to identify the levels of skin-damaging UV radiation:

0-2	Minimal
3-4	Low
5-6	Moderate
7-9	High
10	Very High
10+	Extreme

The UV index depends directly on the solar elevation above the horizon. On a daily basis the UV index will be higher around local solar noon (11:00 AM to 1:00 PM) depending on the time zone. Clear sky days in the winter will have lower UV index values than clear sky days in the summer due to the higher solar angles in the summer.

Hourly UV Index

The hourly index monitors how observed hourly changes in the sky conditions impact the skin-damaging solar UV radiation. The hourly UV index factors in cloud cover, visibility, and present weather conditions in addition to atmospheric ozone concentration, solar elevation and altitude above sea level.

Forecast UV Outlook Index

The forecast UV index provides a UV forecast for the next ten days, based on the daily maximum UV index that is expected in a given location. The forecast UV index depends on the following meteorological parameters as predicted by atmospheric models: forecast cloud cover and visibility, atmospheric ozone concentration, solar elevation and altitude above sea level

SUN SAFETY TIPS

· When possible, avoid outdoor activities during the hours between 10 AM and 4 PM, when the sun's rays are the strongest.

· Always wear a broad-spectrum (protection against both UVA and UVB) sunscreen with a Sun Protection Factor (SPF) of 15 or higher.

· Be sure to reapply sunscreen frequently, especially after swimming, perspiring heavily or drying off with a towel.

· Wear a hat with a 4-inch brim all around because it protects areas often exposed to the sun, such as the neck, ears, eyes, forehead, nose and scalp.

· Wear clothing to protect as much skin as possible. Long-sleeved shirts, long pants, or long skirts are the most protective. Dark colors provide more protection than light colors by preventing more UV rays from reaching your skin. A tightly woven fabric provides greater protection than loosely woven fabric.

· To protect your eyes from sun damage, wear sunglasses that block 99 to 100 percent of UVA and UVB radiation.

· Swimmers should remember to regularly reapply sunscreen. UV rays reflect off water and sand, increasing the intensity of UV radiation and making sun protection especially important.

UV RADIATION

UV OUTLOOK INDEX

Forecast UV Outlook Index

SUN SAFETY TIPS