Ultraviolet Light Exposes
Hidden Germs & Bacteria

By Roger McFadden
Technical Director
Coastwide Laboratories
Portland, Oregon


Ultraviolet light causes certain materials to “fluoresce” or to emit visible light in total darkness. A material
that will fluoresce intensely when exposed to ultraviolet light is flavins. Flavins are found in Vitamin B.
Uric acid, uric salts and soap scum contain Vitamin B. Scientists have found that bacteria and germs
accumulate on surfaces where high concentrations of flavins reside.

Uric acids and soap scum are commonly deposited on restroom fixtures including toilets, urinals, walls,
partitions, mirrors, floors and counter tops. When ultraviolet light is shined on surfaces with uric acid or
soap scum deposits they reflect and emit visible light to the naked eye when viewed in total darkness.
Areas exposed frequently to urine and/or soap products need to be thoroughly cleaned and disinfected to
prevent the accumulation of flavins, which will result in germ growth. Germ growth can lead to odor
problems and create an unhealthy restroom environment.

Restrooms can be inspected with the use of an appropriate ultraviolet light. This can be intimidating to
some custodial personnel. A more positive application of ultraviolet light is to train custodial personnel by
exposing the areas where bacteria commonly are found. The visualization of these areas will guide the
custodian and provide a road map for better cleaning and disinfection of the restroom environment.

Note: Ultraviolet lights are commonly referred to as “black lights”.