7. Exposure to Solar Ultraviolet Radiation on Earth

About 95 % of total solar radiation reaching Earth’s surface comprises of visible (380 to 750 nanometers, nm wavelengths) and infrared (700 to 1 x 10⁶ nm wavelengths) regions of the electromagnetic radiation spectrum. Remaining 5 % of total solar radiation reaching Earth’s surface comprises of ultraviolet (UV) (100 to 400 nm wavelengths) region of the electromagnetic radiation spectrum. The UV region of the electromagnetic radiation spectrum is divided into three bands, namely UVA band between 315 and 400 nm wavelengths, UVB band between 280 and 315 nm wavelengths and UVC band between 100 and 280 nm wavelengths. Excessive exposure to solar UV radiation can cause very serious health effects on our skin, i.e. skin cancer, to our eyes, i.e. cataracts, and to our immune system. Also, exposure to solar UV radiation has cumulative adverse effect on human health.