Ultraviolet index

The ultraviolet index (UVI) is an international standard measurement of the strength of ultraviolet (UV) radiation from the Sun at a particular place and time. It is primarily used to help people protect themselves from the harmful effects of UV radiation, which can cause sunburn, skin cancer, and other health issues.

History

The concept of the UV index was developed in the early 1990s by Canadian scientists as a way to inform the public about the risks of UV exposure. It was later adopted by the World Health Organization (WHO), the United Nations Environment Programme (UNEP), and the World Meteorological Organization (WMO) as a global standard.

Measurement

The UV index is calculated based on several factors, including the angle of the sun, the amount of ozone in the atmosphere, and the presence of clouds. It is expressed as a number on a scale, typically ranging from 0 to 11+, where higher values indicate a greater risk of harm from unprotected sun exposure.

Scale

The UV index scale is divided into categories that indicate the level of risk:

• 0-2: Low
• 3-5: Moderate
• 6-7: High
• 8-10: Very High
• 11+: Extreme

Health Effects

Exposure to UV radiation can lead to various health effects, including:

• Sunburn
• Skin cancer, including melanoma
• Cataracts and other eye damage
• Premature aging of the skin

Protection

To protect against UV radiation, it is recommended to:

• Wear protective clothing, such as hats and long sleeves
• Use sunscreen with a high sun protection factor (SPF)
• Seek shade during peak sun hours
• Wear sunglasses that block UV rays

Related pages

• Ozone layer
• Sunburn
• Skin cancer

Gallery

Global UV index map

UV index forecast for New York City

Erythemal action spectrum

References

UV Index(link). World Health Organization.

Accessed October 10, 2023.

Understanding the UV Index(link). United States Environmental Protection Agency.

Accessed October 10, 2023.

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