What is UV light?

UV light, or more correctly UV radiation, is, like visible light, x-rays and radio waves, a kind of electromagnetic radiation. The wavelengths of UV light are slightly shorter than those of visible light.

Just as visible light is divided into different colours, UV radiation is also divided into groups: UVA, UVB and UVC. UVC has the shortest wavelength (100-280 nm) and all UVC from the sun is absorbed in the upper part of the atmosphere. UVB has a lightly longer wavelength (280-315 nm) and part of it does make it all the way down to the Earth. UVA radiation has the longest wavelength (315-400 nm) and is hardly absorbed at all in the atmosphere.

UV light for treatment and disinfection

The cleaning and bactericidal effects of the sun were discovered back in 1877. In 1908, Niels Ryberg Finsen was awarded the Nobel Prize in Physiology/Medicine for discovering that ultraviolet light beams had a positive effect on, among other things, cutaneous tuberculosis.

A first facility for the UV treatment of potable water was commissioned in Marseilles, France in 1910, after which the technology spread to the USA. In the 1930s, however, UV disinfection was abandoned because of technical shortcomings. Around 1990, there was a renaissance in UV treatment when it was discovered that UV radiation made it possible to effectively treat two microorganisms that had proven to be highly resistant to chlorine. Interest in UV disinfection has been growing steadily since then. It is UVC light that is used for treatment and disinfection.

UV light and safety

Like all UV radiation, UVC can be harmful to human beings. Direct exposure to UVC should therefore be avoided. UVC is, however, effectively blocked by a number of different materials, including glass and most plastics. Nor does UVC generate any residual products that have to be wiped away or neutralised after disinfection.