What is ultraviolet (UV) disinfection? Is it effective? Does it kill Coronavirus?
Many people recognize UVB and UVA light as the ultraviolet light from the Sun that encourages the use of sunglasses and sunscreen. Many of us are not aware that the Sun produces another type of UV light: UVC.
The Sun also emits UVC light, but the Earth’s ozone layer and atmosphere completely block it. Since 1877, scientists have studied the unique antimicrobial properties of UVC. Interest in UV disinfection and its usefulness continues to be researched.
The two main uses of UV disinfection include Ultraviolet germicidal irradiation (UVGI) and Far-UVC. Decade-long studies prove similar efficiency of both and how they produce different effects.
Ultraviolet light is characterized by its shorter wavelength than visible light. Each type operates at different lengths:
- UVA at 315-400 nanometers (nm)
- UVB at 280-315 nm
- UVC at 100-280 nm
The wavelength of UV reaches its maximum bacterial effect at 240-280 nm. Because of its shorter, more active wavelength, UVC exhibits disinfecting properties. So far, studies into UVC cover its use in drinking water, air, public spaces, surfaces, and healthcare facilities.
Since 1878, scientists artificially produce UVC to destroy the genetic material of bacteria and viruses.
This source establishes itself as fundamental for sanitizing drinking water. Because of the no-touch and residual-free characteristics, this disinfecting method continues to be employed. However, it cannot clean a room. Cleaning must precede disinfection.
This method utilizes lamp technology, specifically low-pressure mercury discharge lamps. These lamps release shortwave UVC radiation at 254 nm and damage the DNA of the pathogen cell.
What does this mean?
Scientists understand how ultraviolet germicidal irradiation can kill bacteria and viruses through DNA destruction. The process works best in areas with mold, viruses, bacteria and other pathogens in air or water.
UVGI’s popularity stems from its efficient approach to limiting airborne viral transmission. However, it imposes a hazard on humans, possibly causing cancer and cataracts, so widespread use is limited.
UVGI’s most widely accepted use occurs in water disinfection. It has been shown to be useful in HVAC and upper-room applications, as well. Health-care facilities limit this type of irradiation for routine decontamination of surgical equipment, destruction of airborne organisms, and deactivation of microorganisms on surfaces.
Because of safety hazards, UV operators need adequate training. Large operators of UVC products, like Clorox and Tru-D SmartUVC, offer training to applicants.
Because of the potential health hazards, a group of researchers from Columbia University started researching safe UVC wavelengths for the public.
They discovered Far-UVC, which has a shorter wavelength than conventional UVC. It is only a few nanometers down the UV spectrum and offers a safer solution. Far-UVC operates between 205-225 nm and is usable in occupied rooms.
The higher energy in this wavelength helps destroy the pathogen cell’s structure, not just the DNA. One of the first studies Columbia University conducted showed how aerosolized influenza viruses were disrupted once exposed to the 222-nm far-UVC.
Over time, far-UVC proved efficiency in upper-room applications, similar to UVGI, in hospitals and public spaces. Uninterrupted low doses have shown powerful results against the seasonal influenza epidemic.
Because far-UVC allows the air and surfaces to be properly disinfected without removing people, its efficiency is being tested during the Coronavirus pandemic. Covid-19 often spreads through droplets from coughs and sneezes in the air. A tool that properly inactivates the virus and safely be used around people urges public health interest.
The urgency surrounding Covid-19 preoccupies the public health field.
No cure or vaccination exists for COVID-19.
However, previous and current studies examine the efficiency of UVC on different coronaviruses.
SARS-COV resulted in debilitation when exposed to UVC light at 3 cm for 15 minutes. After 15 minutes, full deactivation occurred.
All human coronaviruses possess similar DNA size and different strains experienced similar deactivation efficiency to far-UVC.
This study found two coronavirus strains to show similar high sensitivity to far-UVC deactivation.
More than 99.9% of seasonal coronaviruses in airborne droplets were killed when exposed to Far-UVC.
Research is still needed but these trials and evidence signal possible treatment and feasibility in public areas.
Standard testing methods, comparisons of different UV systems, and more convenient ways to utilize UVC in various environments require further research.