UVC is a form of Ultraviolet light that kills bacteria and viruses. Its safety for use amongst humans depends on the wavelength of light that is used. “Far UVC” is considered safe while other wavelengths somewhat less so, and of course UVC is not a safety concern if the lighting does not fall on humans. UVC lighting is extremely cost effective with many bulbs available for sale to consumers via Amazon etc for less than $20. UVC bulbs are mercury fluorescent type (e.g. Philips) as well as LED based.
Read this white paper to learn more.