Ultraviolet (UV) radiation is part of the electromagnetic
spectrum emitted by the sun. Whereas UVC rays (wavelengths of
100-280 nm) are absorbed by the atmospheric ozone, most
radiation in the UVA range (315-400 nm) and about 10 % of the
UVB rays (280-315 nm) reach the Earth’s surface. Both UVA and
UVB are of major importance to human health. Small amounts of UV
are essential for the production of vitamin D in people, yet
overexposure may result in acute and chronic health effects on
the skin, eye and immune system. At the United Nations
Conference on Environment and Development (UNCED) in 1992 it was
declared under Agenda 21 that there should be activities on the
effects of UV radiation. In response to Agenda 21, WHO in
collaboration with the United Nations Environment Programme, the
World Meteorological Organization, the International Agency on
Cancer Research and the International Commission on Non-Ionizing
Radiation Protection set up INTERSUN, the Global UV Project.