Explained: What are UV-C Disinfection Systems and does Ultraviolet-C kill SARS-CoV-2?
To mitigate the airborne transmission of SARS-CoV-2, UV-C Disinfectant Systems will soon be installed in Parliament. The Ministry of Science and Technology mentioned in a release that the technology has been tested to disinfect air more than 99% but has not mentioned the wavelength or duration of UV-C light.
Developed and engineered by CSIR-CSIO, UV-C disinfectant systems will prevent the spread of COVID-19 like viruses, fungi, mould, bacteria, and so forth.
UV-C Disinfection Systems
1- The UV-C disinfection system is designed to fit into any existing air-ducts with a few modifications.
2- The virucidal dosages using UV-C intensity and residence time have been optimized according to the existing spaces after considering the necessary airflow rates, shape and size of the air duct.
3- The virus is deactivated in any aerosol particles or freely floating virus or bacteria in the air and at the surfaces of the air ducts by the calibrated levels of UVC light.
4- It can be installed in auditoriums, malls, buildings, educational institutions, AC buses, railways washrooms, etc.
Features of UV-C Disinfection Systems
1- Ergonomic design
3- Maintenance Friendly
4- Optical Modelling and Analytics for Correct Dosage
5- CFD Analysis and Implementation in Duct Design
6- Prevents Dust and Particulate Matter IP-55
7- UV-Sealing & Leak Proof
8- Approved and Valid Certifications
9- UV-C Spectrum and Intensity Test Reports (CSIR-CSIO, ICMR Designated)
10- Virucidal Dose Validation (CSIR-IMTECH Chandigarh)
11- Valid Documentation
What is Ultraviolet (UV)?
Ultraviolet (UV) is a type of radiation that is emitted by the Sun. It has more energy than radio waves or visible light but less energy than X-rays or gamma rays. It has a wavelength range of 100-400 nm.
Types of UV rays
UV rays are divided into three bands-- UV-C (100-280 nm), UV-B (280-315 nm) and UV-A (315-400 nm).
UV-A and UV-B rays emitted by the Sun are transmitted through our atmosphere while UV-C rays are blocked by the ozone layer.
UV-A rays: It has the lowest amount of energy and penetrates to the middle layer of our skin, causes ageing of skin cells and indirect damage to cells’ DNA.
UV-B rays: It reaches the outer layer of our skin, cause sunburns and are associated with skin cancer.
UV-C rays: It has the highest amount of energy and causes skin burns and eye injuries and is linked with an artificial source.
Does UV-C kill SARS-CoV-2?
For years, UV-C has been used to disinfect the air in hospitals, laboratories, and also in water treatment, however, these treatments are carried out in unoccupied rooms to avoid any health problems.
In June 2020, a paper published in Scientific Reports noted that UV-C radiation can destroy the outer protein coating of the SARS-Coronavirus. It showed that far UVC light efficiently kills airborne human coronaviruses-- alpha HCoV-229E and beta HCoV-OC43, different from SARS-CoV-2.
At present, there is limited data on how much wavelength and duration is needed to inactivate SARS-CoV-2.
Researchers at Hiroshima University carried out an in-vitro experiment which was published in September 2020 in the American Journal of Infection Control. The study noted that 99.7% of SARS-CoV-2 viral culture was killed when exposed to 222 nm UV-C irradiation at 0.1 mW/cm2 for 30-seconds.
In March 2021, another study was published in Scientific Reports. It noted that UV-C irradiation was highly effective in inactivating SARS-CoV-2 replication with 16.9 mJ/cm2.
In 2018, a team of researchers at the Center for Radiological Research demonstrated that far UV-C light can help control the spread of airborne-mediated microbial diseases.
Are UV-C Disinfectant Systems safe for humans?
IIT Kanpur researchers who developed UV-C based portable disinfectant device stated that the device was specifically developed to disinfect non-living things.
The paper published in June 2020 noted, "UV-C radiation used in this device could be harmful to the skin and eyes of the living beings, therefore the operator of the device must use spectacles with UV-C radiation protection and use this device safely."
On the contrary, a few studies concluded that far UV-C light (207–222 nm) does not harm mammalian skin as it has a very limited range and cannot penetrate through the outer dead-cell layer of human skin or the tear layer in the eye, so it’s not a human health hazard.