Knowledge about killing coronavirus by UV light. Which is better? UV or UV-C Light?

Which is better for killing coronavirus? UV or UV-C Light?


Applications of UV-C

Ultraviolet C (UV-C) can be used to kill germs in drinking water, replace chlorine as a water disinfectant in swimming pools, kill bacteria in washing machines and dishwashers, kill airborne bacteria in air purifiers and HVAC systems, and treat hospitals The surfaces are disinfected, kitchens, schools, offices and nursing homes. Recently, UVC-launching robots have been cleaning floors in hospitals. Banks have even been sterilizing their money with lights.


What are UV-A, UV-B and UV-C?

The invisible radiation includes a wavelength range of 100 nm to 400 nm. Ultraviolet(UV) rays can be further subdivided and divided into four separate areas:


Most natural ultraviolet rays are produced by the sun, about 10% of sunlight is ultraviolet rays, and only 3% to 4% of ultraviolet rays penetrate the atmosphere to reach the ground. Of the ultraviolet radiation that reaches the earth, 95% is UVA and 5% is UVB.

The sun has no measurable UVC to reach the surface of the earth. Due to the spectral sensitivity of DNA, only the UVC region shows significant bactericidal properties.


How does UV-C disinfection work?

As evidenced by multiple studies and reports, when biological organisms are exposed to deep ultraviolet light in the range of 200 nm to 300 nm, they are absorbed by DNA, RNA, and proteins.


Protein absorption can cause cell wall rupture and biological death. It is known that the absorption of DNA or RNA (especially thymine bases) inactivates the DNA or RNA double helix by the formation of thymine dimers. If enough of these dimers are produced in DNA, the DNA replication process will be interrupted and the cell will not be able to replicate.


Cells that cannot replicate, cannot infect

It is generally believed that it is not necessary to use ultraviolet light to kill pathogens, but to apply enough ultraviolet light to prevent organisms from replicating. The UV dose required to prevent replication is several orders of magnitude lower than the UV dose required to kill, making the cost of UV treatment to prevent infections commercially viable.



Ensuring complete inactivation

Generally, in bacteria, many different repair mechanisms have been developed to repair these ultraviolet-induced lesions. These mechanisms include direct reversal of damage by photolyase (photoactivation), removal of damaged bases by DNA glycosylase (base excision repair, BER), and endonuclease (UV damage endonuclease, UVDE) Or remove the complete oligonucleotide containing damage (nucleotide excision repair, NER). As a result, the strategy for UV disinfection is to provide a sufficiently high dose to ensure that the nucleic acid is damaged and cannot be repaired.



How do UV light sanitizers work?

On the UV light spectrum there are UV-A, B, and C lights. Only the UV-C light can kill germs, says Philip Tierno, PhD, a clinical professor in the department of pathology at New York University Langone Medical Center.


“This light has a range of effectiveness, which interferes and destroys the nucleic acids of bacteria and other microbes,” Tierno explained, adding that the range of light can also disrupt proteins in the microbes by killing certain amino acids. They work best on smooth surfaces and have limitations, Tierno advised.



Hazards to exposing UV-C to skin or eyes

UV-C is really nasty stuff – you shouldn't be exposed to it – Dan Arnold, who works for UV Light Technology, a company that provides disinfecting equipment to hospitals, pharmaceutical companies and food manufacturers across the UK. “UV-C is really nasty stuff – you shouldn't be exposed to it,” says Arnold. “It can take hours to get sunburn from UV-B, but with UV-C it takes seconds. If your eyes are exposed… you know that gritty feeling you get if you look at the sun? It’s like that times 10, just after a few seconds.” So, don’t directly expose your skin or eyes to the UV-C.







  • How to sanitize your phone and other tech, according to doctors”; April 15, 2020, by Jessica Migala, Gideon Grudo and Megan Foster;
  • “There’s only one type of UV that can reliably inactivate Covid-19 – and it’s extremely dangerous”; 24th April 2020, by Zaria Gorvett;