Let's see what Dr. Kevin Khan has to say ;
Deep ultraviolet (UVC) light emitting diodes (LEDs) are an irradiation source and require due precautions to ensure safe usage. This page contains information intended to familiarize users with the current understanding of some of the general practices and precautions most often recommended in the literature for UV irradiation sources (further information is provided in this application note). It is not meant as an exhaustive review on the topic. Currently, there are no work place related rules and regulations that are set by OSHA (Occupational Safety and Health Association) in regard to UVC environmental health and safety.
UV Light and Health Effects The UV range of the electromagnetic radiation spectrum extends from 10 nm to 400 nm. Depending on the wavelength and time of exposure, UV radiation may cause harm to the eyes and skin. The UV spectrum is separated into four parts: UVA (315 nm to 400 nm), UVB (280 nm to 315 nm), UVC (200 nm to 280 nm) and UV Vacuum (100 nm to 200 nm). Decreasing wavelengths correspond with higher frequency radiation and a higher amount of energy per photon. Learn more about UVC and how it works for disinfection
Biological Effect of UV Light While UVB radiation is widely recognized for its harmful effects on human skin and links to skin cancer, each of the UV bands (UVA, UVB and UVC) create different risks for humans. UVC radiation refers to wavelengths shorter than 280 nm. These wavelengths are entirely absorbed by our atmosphere and no natural UVC radiation reaches the surface of the earth. These wavelengths are available to us through artificial sources, such as UVC LEDs or mercury lamps. The intensity from point sources like UVC LEDs falls off as 1 over distance squared, and once it gets past the scattering length, it falls off exponentially. This means that 1) the further away the UVC source from a human, the lesser dose he is exposed to, and 2) the absorption length of UVC radiation in human skin is extremely short so that almost no UVC radiation can reach the living cells in the skin; all the absorption occurs in the dead cell layers.
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