UV Light
Ultraviolet (UV) light is non-ionizing radiation that has a wavelength between X-rays and
visible light in the electromagnetic spectrum (11). The UV spectrum can be subdivided into UVA
(315-400 nm), UV-B (280-315 nm), UV-C (200-280 nm), and the vacuum UV range (100-200
nm) (Fig 2.1). While UV-A is responsible for changes in human skin called tanning, UV-B can
cause skin burning and eventually lead to skin cancer. UV-C is the germicidal range as it
effectively inactivates bacteria and viruses. Vacuum UV can be absorbed by almost all
substances and can only be transmitted in a vacuum (58).
UV-C light has been approved by U.S. Food and Drug Administration (FDA) as an
intervention technology to decontaminate liquid foods and water, food contact surfaces, and food
surfaces (93). The first application of UV was in the disinfection of water, and it remains so
today. Other than water treatment, UV is used as a surface treatment since it is absorbed by most
materials and is unable to penetrate beyond the surface of solid objects (80). UV radiation
between 250 and 260 nm is lethal to most microorganisms, such as bacteria, viruses, protozoa,
mycelial fungi, yeasts, and algae (11). UV generated using low-pressure mercury lamps emits
UV primarily at 254 nm. This wavelength is the most efficient as it is absorbed most by nucleic
acids (58). The germicidal effects of UV at 254 nm is therefore used for disinfection of surfaces,
water, and some food products (37).
UV radiation offers some other advantages over existing sanitation methods: it does not
leave any residue; it does not have legal restrictions; it does not require installation of extensive
safety equipment (100, 104); it is easy to use; and it is economical (11). The only disadvantage is
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the limited penetration (74). The efficacy of UV light depends on the surface structure and
topography (34), the doses applied, and the distance between the UV light source and the treated
sample (29). Temperatures between 5 and 37°C have little, if any, impact on the effectiveness of
UV-C light (56).