According to a new study, 99.9% of seasonal viruses in airborne droplets were destroyed after exposure to a particular wavelength of ultraviolet light (Far-UVC) without any risk of harm to humans.
This is an important advance in the field of virology, especially in the study of seasonal coronaviruses. While the UV light trail was already looked into for decontaminating surfaces that come into contact with the new COVID-19 virus, a new study by Columbia University’s Irving Medical Center shows that UV light can be a valuable ally in killing airborne coronaviruses.
“Based on our findings, continuous air disinfection with far-ultraviolet light (Far-UVC) at the current legal limit could significantly reduce the number of airborne viruses in indoor areas where people gather,” said David Brenner, lead author of the study published in Scientific Reports.
99.99% of coronaviruses dead in 25 minutes
At present, the UV-C germicidal light used has a wavelength of 254 nm. It is used in particular to disinfect unoccupied rooms such as hospital rooms and empty subway cars. However, exposure to such a wavelength is not possible if these rooms are occupied, as it could pose a health risk.
The light tested by researchers at Columbia University’s Irving Medical Center has a wavelength of 222 nm: It cannot penetrate the tear layer of the eye or epidermis, so it cannot reach or damage living cells in the body.
To test its effectiveness, scientists used a misting device to spray two common coronaviruses. The coronaviruses were then sprayed into the air in front of a remote ultraviolet lamp. After being exposed to the distant ultraviolet light, the researchers conducted tests to see how many viruses were still alive.
The results were conclusive: 99.9% of the viruses died after very low exposure to ultraviolet light. Specifically, 90% of airborne viruses died after about 8 minutes of exposure, 95% in about 11 minutes, 99% in about 16 minutes, and 99.9% in about 25 minutes.
These results are encouraging and give hope for the use of Far-UVC lamps in occupied public indoor spaces. This could significantly reduce the risk of human-to-human transmission of coronaviruses and influenza viruses.
A possible use against COVID-19
Another ongoing study is testing far UVC light against SARS-CoV-2. Preliminary data are positive. “Far UVC light doesn’t really distinguish between types of coronaviruses, so we thought it would kill SARS-CoV-2 in the same way,” said David Brenner. Because SARS-CoV-2 is largely spread by droplets and splashes that are spat out and sneezed into the air, it is important to have an instrument that can safely inactivate the virus when it is in the air, especially in the presence of people.
“Since it is safe in occupied spaces such as hospitals, buses, planes, trains, stations, schools, restaurants, offices, theaters, gyms and any other place where people are indoors, Far UVC light could be used in combination with other measures, such as the use of masks and hand washing, to limit the transmission of SARS-CoV-2 and other viruses,” he concluded.