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Ultraviolet C, or UV-C light, exposure has been associated with the reduction of microorganisms on surface areas.1 But how exactly does UV-C light inactivate them? Let’s take a closer look at the process.
What is UV-C Light?
Ultraviolet, or UV light, is a type of radiation that is part of the electromagnetic spectrum. It is invisible to the human eye and its wavelengths range from 100 to 400 nanometers (nm).2
UV light can be of lower frequencies, or with long wavelengths of 280 to 400 nm. This type of UV light is known as Ultraviolet A and Ultraviolet B (UV-A and UV-B) light. Higher-frequency UV light, with shorter wavelengths of 100 to roughly 200 nm, is known as vacuum UV light.3
Ultraviolet C (or UV-C) light is a type of UV light that has wavelengths that range from 200 nm to 280 nm.4 5
UV-C light waves are comprised of photons, or particles of light. They are the most energetic of the optical electromagnetic spectrum (comprised of UV, visible, and infrared light) and are, therefore, the most photochemically active.
UV-C light occurs in natural sunlight, but it is blocked by the atmosphere and does not reach the earth’s surface. UV-C light, however – especially at wavelengths of 254 nm – can be replicated in the form of UV lamps, and these UV-C lamps can be used in environmental disinfection procedures.6
These procedures are intended to be antimicrobial in nature. Indoor surfaces exposed to 254 nm UV-C light, for example, have been found to have fewer microorganisms than surfaces without such exposure, according to several studies.7 8 9 For this reason, UV-C light has been associated with decreased levels of surface microorganisms and is also known as ultraviolet germicidal irradiation, or UVGI.10
UV-C light has been associated with reductions of microorganisms in liquids,11 on surfaces,12 and even in the air.13 Though the way UV light interacts with these microorganisms is not entirely clear, disinfection is thought to be associated with the molecular breakdown of nucleic acids.14
Organisms and nucleic acids
All living organisms contain nucleic acids, which themselves are polymers, or large groups of repeating molecules.15 Nucleic acids are essential components of all life forms and appear as deoxyribonucleic acid (DNA) and/or ribonucleic acid (RNA) in microorganisms and larger life forms.16
DNA and RNA, as nucleic acids, are themselves comprised of molecular compounds. DNA contains the nitrogen-containing compounds:
- Cytosine (also known as C)
- Guanine (G)
- Adenine (A)
- Thymine (T)
Together with other molecules, these compounds form structures called nucleotides. Nucleotides form sequences in DNA that serve as codes for biological functions, and these sequences are also known as genes.17
An organisms’ genes play a unique role in its biological activity. In particular, genes inform and mobilize an organism’s: - growth
- reproduction
- function
- development
The DNA of a certain gene may be copied or otherwise replicated during cell division, and changes to this DNA, or an environment’s effects on it, may impact an organism’s survival.18
UV-C light and microorganisms
In terms of environmental effects, the presence of 254 nm UV-C light has been associated with a degeneration of nucleic acids – such as DNA and RNA. In DNA specifically, UV-C light seems to start a reaction between molecules of thymine, creating thymine dimers.19 Thymine dimers are essentially components of thymine that have been broken down into two parts.20
Normally, a microorganism's repair process will remove thymine dimers and replace them, to once again form an intact DNA strand.21 With prolonged exposure to UV-C light, however, there is a greater chance that the replacement process will go wrong.
An inhibited thymine replacement process will create damaged cellular DNA – DNA that cannot be adequately repaired.22 In this way, UV-C light exposure has the potential to cause a debilitative reaction in all types of organisms. On a smaller scale, the damaged cellular DNA will cause death among exposed microorganisms.23
Indeed, some studies have shown that devices emanating 254 nm UV-C light can reduce microorganisms at rates of over 99.9%.24 25 In terms of logarithmic ratios that describe contamination levels, this rate would represent an over 3-log reduction in environmental microorganisms.
UVD Robots and UV-C Light
UVD Robots (with UVD standing for Ultraviolet Disinfection Robots), are self-driving UVGI disinfection robots. UVD Robots are developed and produced by the Danish company Blue Ocean Robotics, and use 254 nm UV-C light for environmental disinfection purposes.26
As self-navigating robots, UVD Robots are able to irradiate indoor environments with UV-C light in multiple areas, more so than stationary systems.27 UVD Robots, as mobile UV-C devices, are capable of over 3-log reductions of microorganisms, or an efficacy rate of over 99.9%. 28 29
UVD Robots Utilize UV-C Light to Reduce Environmental Microorganisms by 99.99%
The presence of UV-C light has been associated with environmental microorganism reduction, and its effects appear to initiate on a molecular level.
There may be an association between exposure to UV light and deterioration of nucleic acids, notably of the DNA compound thymine. This deterioration appears to happen when damage to the thymine compounds occurs faster than they can be repaired.
UVD Robots are mobile disinfection robots that emit 254nm UV-C light. As autonomous robots, they are especially potent against several environmental microorganisms and can reduce them at efficacy rates of 99.99%.
Explore the Power of UVD Robots: Download Declaration overview on UV Disinfection Effectiveness
