Ultraviolet-C (UVC) light is within the electromagnetic spectrum, which is divided into categories based on wavelength. Other recognizable categories include radio waves, microwaves, infrared light, visible light, X-rays, and gamma-rays.
Credit: NASA's Imagine the Universe
Our sun produces electromagnetic radiation, as do other celestial bodies such as stars and galaxies. Ultraviolet light is a shorter wavelength than visible light, and is usually divided into three sub-categories:
UVA (315-400 nanometers)
UVB (280-315 nanometers)
UVC (180-280 nanometers)
The shorter the wavelength, such as UVC, the more damage can be done. UVC does not reach the surface of the earth due to the protective properties of the atmosphere, while UVA accounts for 95% of the UV that does, with UVB accounting for the other 5% (Lucas 2017). This is a good thing, as UVC with its short wavelength, is the most damaging of the three to our DNA, or deoxyribonucleic acid, the genetic material of our cells.
The higher energy wavelengths of UVB and UVC cause mutations in DNA to form. DNA and RNA (ribonucleic acid, which is made from DNA) have 4 building blocks known as nucleotides (think of them as small legos that build a bigger structure). These nucleotides are in two categories- purines and pyrimidines. Purines include the bases adenine and guanine, while the pyrimidines include thymine in DNA/uracil in RNA and cytosine. The UVC causes pyrimidine dimers to form.
All DNA/RNA copying and processing that is required for replication of an organism or virus needs two protein workers (enzymes) known as DNA polymerases and RNA polymerases. With the pyrimidine dimer mutation, these copiers cannot do their job, and the damaged DNA/RNA is unable to be used.
The mutation-producing property of UVB can lead to skin cancer in humans, but with the use of UVC as a germicide inside buildings, it means an incredibly useful tool for preventing airborne infections because it leads to the inability of germs like viruses, bacteria, and mold to replicate and spread.
The utilization of UVC as a germicide has been tested and used for over a century, and with COVID-19 posing a barrier to re-opening the economy, a wide-scale implementation of this technology is being evaluated by many businesses. With the technology enclosed in a safe barrier to prevent damage to humans, this is a safe and effective tool.