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SunUVStationTM: Background Information About the UV Index
The SunUVStation displays a number called the "UV Index." The UV
Index is a standardized scale indicating the intensity of the sun's UV
radiation that affects human skin. (UV can also damage eyes) The UV
intensity varies from one place to another, and in the same location it
varies throughout the day and as the seasons change. The variations are
caused by the sun's changing position in the sky, clouds, the altitude,
and other factors, so each location has its own range of UV index values from
dawn to sundown. The UV Index is used in the United States, Canada,
Australia, New Zealand and many other countries by agencies such as the
US Environmental Protection Agency and Environment Canada.
The higher the UV Index, the more care you should take when working,
playing or exercising outdoors. For most places on Earth the Index will
read between 1 and 15, but some high altitude places such as the Mauna
Loa Observatory in Hawaii have measured a UV Index of 20. The UV
Index can make a large difference in the amount of time you can spend in
the sun before sunburn. For example, if you are very fair skinned and are
not using sunscreen or wearing protective clothing, you could spend an
hour or more in the sun without sunburn on a low UV index day (1 to 2),
but have less than 10 minutes before sunburn on a day with a UV Index
of 10. The UV Index stated in newspapers and broadcast media weather
reports in the USA is a forecast from the National Weather Service of the
highest reading for the day for a general area. The SunUVStation
provides a continuous actual measurement of the UV Index for the
specific location it is in. In addition to the numbers, UV Index ranges are
described in categories and with colors:
Protecting Skin from Too Much UV
The amount of UV that skin can tolerate before it burns varies greatly
from one person to another. But even if it were possible to stop UV
exposure just short of sunburn, this is not advised. Tanned skin is
considered damaged and tanning is the skin's attempt to prevent further
damage. The World Health Organization (WHO) recommends that any
time the UV Index is greater than 2 you should take precautions to limit
sun exposure with sunblock, a hat and shirt, and limit time in the sun as
the index moves to higher values. The WHO has established general
guidelines for protective measures and sun avoidance based on the UV
Index. These are shown in the chart below.
The US EPA's site for the "Sunwise" UV awareness program:
http://www.epa.gov/sunwise/
The World Health Organization site:
http://www.who.int/uv/en/
A color pamphlet from WHO on the UV Index:
http://www.who.int/uv/publications/en/GlobalUVI.pdf
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