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Updated: Sep 24, 2020

First proof that safer 222nm UV-C effectively kills SARS-CoV-2

A study by Hiroshima University has found that using UV-C light with a wavelength of 222nm which is safer to use around humans effectively kills SARS-CoV-2 — the first research to prove its efficacy against the virus that causes COVID-19 (Hiroki Kitagawa et al, American Journal of Infection Control, DOI: 10.1016/j.ajic.2020.08.022).

Other studies involving 222nm UV-C (far-UVC) have so far only looked at its potency in eradicating seasonal coronaviruses that are structurally similar to the SARS-CoV-2 but not on the COVID-19-causing virus itself.

An in-vitro experiment by Hiroshima University with krypton-chloride excimer lamp, showed that 99.7% of the SARS-CoV-2 viral culture was killed after a 30s exposure to 222nm UVC irradiation at 0.1mW/cm2.

Some UVC appliances around the world

Quick Bites to keep you abreast

  • Annually 99,000 people are estimated to die from healthcare-associated infections (HAIs) in the United States alone, more than 11 people per hour. 

  • HAIs are also estimated to result in Rs 700 billion in medical costs annually. 

  • UV-C emissions are known to cause photo-chemical damage to nucleic acids and proteins, inactivating and thus rendering pathogens incapable of reproducing. 

  • UV-C disinfection devices are therefore useful in healthcare settings to reduce patient and healthcare worker exposure to these pathogens when combined with standard cleaning strategies. 

The LuxLive UV-C Digital Conference to be held on 22 September 2020, will focus solely on the timely and urgent topic of UV-C lighting and its role in helping building managers ensure the highest levels of safety and wellbeing. 

Pros and Cons of UVC LEDs and Lamps for Disinfecting Applications

UVC light incorporated products for disinfection are becoming more and more popular. These UVC light disinfecting products usually deploy either mercury lamps or LEDs as light source. Currently, mercury lamps are more widely adopted for disinfecting products given its lower production cost and higher power output.

However, UVC LEDs featuring smaller size, adoption flexibility and longer lifetime also attract increasing attention in the industry. Both UVC LED and UVC Lamp have been proved to be effective for diminish bacteria and viruses including the pathogen of COVID-19, SARS-CoV-2, with suitable UV intensity and expose time. UV mercury lamps have higher optical power and lower price but are larger and heavier comparing to LEDs, thus limiting its applications. On the other hand, with compacted size, UVC LEDs can be easily integrated with different home appliances like air conditioners, air purifiers or even washing machines.

UVC LEDs are often adopted for portable products. Another edge of UVC LEDs for application is that LEDs can fully operate once turned on and while mercury lamps need preheating while it takes about 10 to 30 minutes for mercury lamps deliver required UV dose for disinfection. Safety: UVC light not only kills virus, it can also cause damages to human skin and eye. The Global Lighting Association has provided guidelines focusing on UVC disinfection products for manufacturers and users

Edit: LEDs emit UVC at 275nm have 20-25% more Germicidal Efficiacy over the mercury lamps.

Urgent Need of Surface Disinfection Powered by UVC LED Technology

The recent outbreak of COVID-19 has prompted many to search for potential ential technologies that can be used to combat the virus. One proven approach is using UV light. Disrupting the DNA of pathogens with UV light UVC light is a commonly used sterilization technology that has been shown to inactivate a wide range of pathogens, including- but not limited to- MRSA, C. diff, E. Coli and Pseudomonas. In application UVC energy is absorbed by nucleic acids inside the RNA and DNA, resulting in covalent bonds which, at the right dose, can render the pathogen unable to reproduce and infect. The most effective germicidal wavelength occurs with a peak between 260 nm to 270 nm, the optimum point at which DNA absorbs UV energy. UV mercury lamps have several limitations, including low activity at refrigeration temperatures, fragile construction, long warm-up time, risk of mercury exposure, and limited UV emittance at 254nm.

In comparison, UV light-emitting diodes (UVC LEDs) can be configured to emit at ideal germicidal wavelengths and provide reliable on-demand disinfection ( instant ON) without the limitations which hamper mercury lamps. UVC LED technology in action These are just two examples of the innovative new products using UVC LEDs to combat COVID-19 and other pathogenic contaminants. Based in Finland, LED Tailor Innova7ion has decades of experience in developing light based disinfection products. Its WiSDOM DS product is a file cabinet like drawer, which uses Klaran UVC LEDs to disinfect electronic devices and other non-critical medical equipment, including blood pressure cuffs and stethoscopes. In California, Cleanbox uses Klaran UVC LEDs in the CX1 cabinet to disinfect VR goggles, head mounted displays and other mass-use hardware worn on the face/head. The unique Cleanbox approach eliminates the need for heat or toxins in the decontamination process, protecting electronics It mitigates the spread of 99.99 percent of bacteria, virus, and fungi in one minute. A viable solution in testing for COVID-19 effectiveness The use of UVC LED technology on surfaces enables reliable, fast, on-demand disinfection for small to midsize devices, such as laptops, phones, keyboards, eyewear, keys and healthcare equipment. It prevents the transmission of harmful microbes into highly sensitive areas, including hospital care units, laboratories and cleanrooms

UVC LEDs have not only proven effective against superbugs, such as C. diff and Methicillin-Resistant Staphylococcus Aureus (MRSA), but also are capable of achieving significant reduction in viral and bacterial loads in seconds. While studies have confirmed that UVC light can be effective for combating SARS-COV additional studies are needed to determine and confirm the specific dose-response required to inactivate COVID-19 on different surfaces and materials. Article provided by Asahi Kasei; author: Shogo Sueyoshi

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