UV Disinfection

Germicidal ultraviolet (UVC) light kills cells disrupting ther cellular membranes and by damaging their DNA or RNA. The UV light initiates a reaction between two molecules of thymine, one of the bases that make up DNA. UV light at 253.7nm wavelength (shortwave UV or UVC) causes adjacent thymine molecules on DNA to dimerize. The resulting thymine dimer is very stable. If enough of these defects accumulate on a microorganism's DNA its replication is inhibited, thereby rendering it harmless.

Ultraviolet photons harm the DNA molecules of living microorganisms in different ways. In one common damage event, adjacent bases bond with each other, instead of across the "ladder". This makes a bulge, and the distorted DNA molecule does not function properly. » See Ultraviolet in Wikipedia, the free encyclopedia

If a microorganism is introduced to a very high UV dose that leads to the disruption of the its cellular membrane and the death of the cell.

The longer the exposure to UVC light, the more thymine dimers are formed in the DNA. If cellular processes are disrupted because of DNA damage, the cell cannot carry out its normal functions and can not reproduce and  microorganisms that can not reproduce can not cause diseases. If the damage is extensive and widespread, the cell will die.

The LIGHT SPECTRUM ranges from the infrared at wavelengths longer than visible light to the ultraviolet at wavelengths shorter than visible light. Ultraviolet (UV) radiation is electromagnetic radiation of a wavelength shorter than that of the visible region.

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