What is UV-C Light and can it kill COVID-19?

Ultraviolet (UV) light is a type of electromagnetic radiation. Natural electromagnetic radiation comes from the sun. Artificial electromagnetic radiation comes from tanning booths, black lights, curing lamps, germicidal lamps, mercury vapor lamps, halogen lights, high-intensity discharge lamps, fluorescent and incandescent sources, and some types of lasers [1].

Either or, electromagnetic radiation it is transmitted in waves or particles at different wavelengths and frequencies. This broad range of wavelengths is known as the electromagnetic (EM) spectrum. The spectrum is generally divided into multiple regions in order of decreasing wavelength and increasing energy and frequency. The common designations are radio waves, microwaves, infrared (IR), visible light, ultraviolet (UV), X-rays, and gamma-rays.

UV light falls in the range of the EM spectrum between visible light and X-rays. It has wavelengths of about 380 nanometers (nm) to about 10 nm. UV is generally divided into three sub-bands [2]:

• UV-A, or near UV (315–400 nm)
• UV-B, or middle UV (280–315 nm)
• UV-C, or far UV (180–280 nm)

WHAT ARE THE DIFFERENCES BETWEEN UV-A, UV-B, & UV-C LIGHTS?

UV-A lighting accounts for 95 percent of the sun's radiation that reaches the earth’s surface. UV-A is also known as "blacklight" and is generally harmless. However, these rays can penetrate the skin's second layer causing wrinkles, sunspots, and other types of premature aging if there is exposure for long periods of time. UV-A is used in tanning beds and can cause temporary and permanent skin changes.

UV-B lighting accounts for the other 5 percent of the sun's radiation that reaches the earth’s surface. These rays tend to damage the skin's top layer and have a very high penetrating ability. Prolonged exposure to UV-B is responsible for some types of skin cancer, skin aging, and cataracts (clouding of the lens of the eye) [3].

UV-C lighting almost never reaches the earth because the ozone absorbs it. UV-C has extremely low penetrating ability and is nearly completely absorbed by the outer, dead layer of skin where it does little harm. It does reach the most superficial layer of the eye where overexposure can cause reddening and painful but temporary irritation, but it cannot penetrate to the lens of the eye and cannot cause cataracts. UV-C short wavelength can disrupt DNA to inactive microorganisms and this is used to sterilize, disinfect, and effectively kill a wide range of viruses and bacterias. UV-C is also known as "germicidal UV"[5].

HOW UV-C (GERMICIDAL UV) CAN KILL COVID-19?

Germicidal UV has a specific wavelength of 253.7 nanometers (253.7 billionths of a meter) and is known to deactivate (break the DNA and RNA) germs. In other words, UV-C can kill 99% of viruses, bacteria, mold, fungus, and yeast through the disruption of the DNA or RNA structure at the cellular level.

When the DNA and RNA of these pathogens are exposed to UV-C radiation, a chemical change occurs in the nucleic acids, resulting in corruption in the genetic code. Once its genetic code has been corrupted, the pathogen is no longer able to replicate itself, quickly resulting in the death and elimination of viral and bacterial colonies. Proper application of UV-C light can viruses such as Coliform, Salmonella, E. coli, Staphylococcus, Listeria, and Anthrax among others. [4].

Despite these viruses having a wide range of different structures and sizes ranging from double-strand DNA viruses to single-strand RNA viruses, the efficacy of the UV-C disinfection across all of these viruses suggests that the likelihood of it also being effective against the COVID-19 coronavirus is quite high.

A study in a Japanese laboratory on the SARS virus showed that exposing the virus to a UV irradiance of 1.34 W/m2 for 15 minutes significantly reduced the infectivity of the sample [5]. A separate study on the same virus showed that UV-C irradiance of 40.16 W/m2 resulted in a "400-fold decrease in infectious virus" after 6 minutes of exposure, with complete inactivation achieved after 15 minutes of exposure [6]. A later 2007 study on the murine coronavirus showed that UV-C radiation resulted in successful air disinfection using a dose of 3 J/m2 [7].

Due to the structure and genetic code similarities of the SARS-CoV-2 coronavirus, it would be reasonable to consider a similar level or mechanism of susceptibility to UV-C sterilization.

CAN I USE UV-C PRODUCTS FOR MY HOME AND BUSINESS BY MYSELF?

Yes. However, there are hundreds of UV products in the market that claim to be effective, safe, and UL certified when they are not. Some of the questions you need to ask yourself prior to purchasing a UV product for disinfection purpose are:

• What application is it for? Air, surface, water?
• How much UV do I need?
• Does it work in the correct wavelength at all times?
• For how long do I need to keep it on?
• Does it have a safety sensor?
• Does it produce ozone? If yes, does it has the minimum levels of ozone to be safe?
• Does it offer the recommended minimum warranty for a UV product?

There many other key elements that play a crucial role in the correct selection of the UV product for your home businesses. We will go through the details of those in the following blogs.

References:

1. Lucas, Jim. "What Is Ultraviolet Light", www,livescince.com

2. "IUVA Fact Sheet on COVID-19", www.americanultraviolet.com

3. "Ultraviolet Rays ", www.uvresources.com/resources/faqs

4. "UV Resources", www.uvresources.com/resources/faqs

5. Hiroaki Kariwa. "Inactivation of SARS Coronavirus by Means of Povidone-Iodine, Physical Conditions, and Chemical Reagents", Dermatology, 2006.

6. Miriam E.R. Darnell. "Inactivation of the coronavirus that induces severe acute respiratory syndrome, SARS-CoV ", Journal of Virological Methods, 2004.

7. Christopher M. Walker. "Effect of Ultraviolet Germicidal Irradiation on Viral Aerosols", American Chemical Society Publications, 2007.