How Safe Is UV-C Light?

(Photo by Serge Kutuzov on Unsplash)

NB: For the purposes of this blog post, we would like to make the distinction between "UV-C" light and "UV" light. UV-C light has the shortest-wavelength of the three types of UV light (UV-A, UV-B, UV-C). With regards to this blog post, we would like to talk specifically about UV-C light only.

It is a well-known fact that UV-C light is highly effective in killing bacteria, viruses & other pathogens by destroying the molecular bonds that hold their DNA together.

However, what are the potential harmful effects (if any) of UV-C light on humans, and to what extent should we take necessary precautions when it comes to UV-C light?

The European Commission, under the Scientific Committee on Health, Environmental and Emerging Risks (SCHEER), notes that UV-C lamps have been used for many decades with only a few known incidents caused by accidental exposure or misuse.

Potential Human Health Hazard
Investigators from the Center for Radiological Research at Columbia University Irving Medical Center (CUIMC) have found that continuous low doses of far ultraviolet C (far UV-C) light can kill airborne flu viruses without harming human tissues. 

However, senior study investigator David Brenner, Ph.D., director of the Center for Radiological Research and professor at CUIMC notes that "conventional germicidal UV light is also a human health hazard and can lead to skin cancer and cataracts, which prevents its use in public spaces."

Other potential health hazards from exposure to UV-C light include corneal injuries, photokeratitis, erythema and skin cancer.

Recommended Maximum Exposure Time
There is no Occupational Safety and Health Administration (OSHA) standard for exposure to ultraviolet light, but the National Institute for Occupational Safety and Health (NIOSH) recommends that the time of exposure to an intensity of 100 microwatts per square centimeter at wavelength 254 nanometers (i.e. UV-C light) not exceed one minute.

Safety Precautions
In view of the potential harmful effects of UV-C light, it is highly advisable to avoid any direct contact with UV-C light, be it with the eyes or skin. Also, in the event of harmful exposure to UV-C light, it is recommended to seek appropriate medical advice from an ophthalmologist or from a skin specialist.

From the above sources, one is able to safely conclude that the key determining factor in all of this is exposure

While UV-C light is considered a safe and widely-used disinfecting tool in a plethora of industrial applications, care has to be taken not to be directly exposed to the UV-C rays for reasons stated above.

As long as care is taken to avoid any form of direct exposure to UV-C rays, then the harmful effects can be deemed to be negligible.