What are the effects of UV rays on human body and materials?

All living organism would be seriously damaged by UV rays from the Sun if a good part of the radiation was not filtered by the Earth's atmosphere. The same goes for radiation emitted by UV-C lamps.

Regarding human or animal body, a continuous irradiation of eyes and skin could cause dangerous sunburns and conjunctivitis. Their germicidal functioning consists in attacking the DNA of microorganisms, damaging their reproductive system and preventing their replication. For this reason it is important to check that before activating the germicidal UV-C lamp, the rooms are free from people, animals and plants and that no one can access the rooms before the end of the disinfestation.

With regards to materials, unlike X or Gamma rays, UVC rays cannot penetrate solid bodies. To eliminate microorganirsm with UV-C rays, it is therefore necessary that they are on the surface of an object or that they are transported by air. Although materials such as ordinary window glass, polycarbonate and other transparente materials allow the light of UV-C lamps to be seen through them, they stop the passage of wavelenght of UV-C lamps, totally canceling their germicidal effect. As far as plastic material, UV-C rays have an effect similar to direct solar rays (even if UV-C rays do not transmit heat) with the consequent yellowing of the materials exposed for too long time, especcialy if white in color.