Ultraviolet Light in Biology and Medicine

It is usual to divide UV radiation in three broad groups, according to its biological effects. These are  

which covers the wavelength region below 290 nm. This radiation is also described as abiotic , that is detrimental to life. It will be seen that this wavelength region corresponds to the direct absorption of UV light by nucleic acids and proteins. The low-pressure mercury arc lamp which emits at 254 nm is known as a bactericidal lamp. 

between 290 and 330 nm, is the deeper region of biotic , that is biologically beneficial, UV radiation. Light of this wavelength region is used for the biosynthesis of vitamin D, and it produces pigmentation of the skin. 

from 330 nm to the onset of the visible (VIS) region at around 390 nm. This is the near UV part of biotic UV radiations, absorbed essentially by the blood cells. 

Natural light (sunlight) at the surface of the Earth contains very little UVA, as this is filtered out by the ozone layer in the upper atmosphere. 

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