摘要：Ultraviolet radiation, risk factor on human health. Everyone is exposed to ultraviolet (UV) radiation from the sun. Small amounts of UV radiation are beneficial to people, and play an essential role in the production of vitamin D. However, overexposure to UV radiation is responsible for two major public health problems: skin cancer and cataract. UV radiation reaching the Earth's surface is largely composed of UVA with a small UVB component; UV radiation levels being influenced by various factors The UV Index is a simple measure of the UV radiation level at the Earth's surface and it has been designed to indicate the potential for adverse health effects and to encourage people to protect themselves. The values of the Index range from zero upward and the higher the Index value, the greater the potential for damage to the skin and eye, and the less time it takes for harm to occur. While the levels of UV radiation vary during the day, they reach a maximum around mid-day. The UVI is usually presented as a forecast of the maximum amount of UV radiation expected to reach the Earth's surface at solar noon, many countries using the UVI to promote sun protection along with the weather forecast in newspapers, TV and radio. Simple precautions will prevent both short-term and long-term damage of UV radiation exposure.
