Union Minister of State for Science and Technology Dr Jitendra Singh has said that Ultraviolet-C or UV-C Disinfection Technology will soon be installed in Parliament for the “mitigation of airborne transmission of SARS-COV-2’’.
The UV-C air duct disinfection system was developed by CSIR-CSIO (Central Scientific Instruments Organisation). CSIR-CSIO mentioned in a release that the system is designed to fit into any existing air-ducts and the virucidal dosages using UV-C intensity and residence time can be optimised according to the existing space. The release adds that the virus is deactivated in any aerosol particles by the calibrated levels of UV-C light. It can be used in auditoriums, malls, educational Institutions, AC buses, and in railways.
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Ultraviolet (UV) is a type of light or radiation naturally emitted by the Sun. It covers a wavelength range of 100-400 nm. The human visible light ranges from 380–700 nm.
UV is 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 from the Sun are transmitted through our atmosphere and all UV-C is filtered by the ozone layer. UV-B rays can only reach the outer layer of our skin or epidermis and can cause sunburns and are also associated with skin cancer. UV-A rays can penetrate the middle layer of your skin or the dermis and can cause aging of skin cells and indirect damage to cells’ DNA. UV-C radiation from man-made sources has been known to cause skin burns and eye injuries.
UV-C radiation (wavelength around 254 nm) has been used for decades to disinfect the air in hospitals, laboratories, and also in water treatment. But these conventional germicidal treatments are done in unoccupied rooms as they can cause health problems.
A paper published in June 2020 in Scientific Reports noted that UV-C radiation can destroy the outer protein coating of the SARS-Coronavirus. They showed that 222-nm, known as ‘far-UVC light’, efficiently kills airborne human coronaviruses – alpha HCoV-229E and beta HCoV-OC43. This is different from SARS-CoV-2 virus. There is very limited data on the required wavelength and duration needed to inactivate SARS-CoV-2.
An in-vitro experiment conducted by Hiroshima University researchers showed 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. The study was published in September 2020 in the American Journal of Infection Control.
Another study published in Scientific Reports in March 2021 noted that UV-C irradiation was highly effective in inactivating SARS-CoV-2 replication. “A complete inactivation at all viral concentrations was observed with 16.9 mJ/cm2. These results are important for the development of novel sterilising methods to contain SARS-CoV-2 infection,” write the authors.
Researchers from the Indian Institute of Technology-Kanpur, who developed a portable disinfectant device that used UV-C radiation (222-254 nm), noted that the device was specifically developed to disinfect non-living things. “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,” noted the paper published in June 2020.
The release from our Ministry of Science and Technology does not state the wavelength or duration used, but mentioned that the product was tested for more than 99% disinfection.
Dan Arnold, who works for UV Light Technology, a company that provides disinfecting equipment to hospitals, pharmaceutical companies across the UK, told bbc.com: “UV-C is really nasty stuff – you shouldn’t be exposed to it…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 10 times, just after a few seconds.”
But few studies have shown that far-UVC light (207–222 nm) does not harm mammalian skin. “Far-UVC light 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. But because viruses and bacteria are much smaller than human cells, far-UVC light can reach their DNA and kill them,” explained David J. Brenner, director of the Center for Radiological Research at Columbia in a release. His team has demonstrated in 2018 that far-UVC light can help control the spread of airborne-mediated microbial diseases.
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