Far-UVC light kills 99.9 percent of airborne coronaviruses

Experts have demonstrated that a type of ultraviolet light known as far-UVC light can kill 99.9 percent of coronaviruses present in airborne droplets. Humans can be safely exposed to this particular wavelength of UV light, which means far-UVC could be used to disinfect the air in public places. 

Study lead author Dr. David Brenner is the director of the Center for Radiological Research at Columbia University Irving Medical Center.

“Based on our results, continuous airborne disinfection with far-UVC light at the current regulatory limit could greatly reduce the level of airborne virus in indoor environments occupied by people,” said Dr. Brenner.

Germicidal UVC light, which is known to deactivate pathogens like bacteria and viruses, is used to disinfect unoccupied spaces such as empty hospital rooms. 

However, germicidal UV lamps cannot be used in occupied public spaces because direct exposure is considered a human health hazard that can cause skin cancer and cataracts.

According to the researchers, far-UVC light cannot penetrate the tear layer of the eye or the outer dead-cell layer of skin so it cannot damage living cells. In previous work, the Columbia team showed that far-UVC light can safely kill airborne flu viruses.

For the current study, the researchers used a misting device to aerosolize two common coronaviruses. The aerosols were released in the air in front of a far-UVC lamp. 

When the researchers tested to see how many viruses were still alive, they found that more than 99.9 percent of the viruses had been wiped out by a very low exposure to far-UVC light.

Based on the results, the researchers estimate that continuous exposure to far-UVC light would kill 90 percent of airborne viruses in eight minutes, 95 percent in 11 minutes, 99 percent in 16 minutes, and 99.9 percent in 25 minutes.

The findings suggest that it may be feasible to use overhead far-UVC lamps in occupied public places to substantually reduce the risk of virus transmission.

The researchers are currently testing the use of far-UVC light to kill SARS-CoV-2. The preliminary results indicate that far-UVC light is just as effective at deactivating airborne SARS-CoV-2.

“Far-UVC light doesn’t really discriminate between coronavirus types, so we expected that it would kill SARS-CoV-2 in just the same way,” said Dr. Brenner.

“Since SARS-CoV-2 is largely spread via droplets and aerosols that are coughed and sneezed into the air it’s important to have a tool that can safely inactivate the virus while it’s in the air, particularly while people are around.”

“Because it’s safe to use in occupied spaces like hospitals, buses, planes, trains, train stations, schools, restaurants, offices, theaters, gyms, and anywhere that people gather indoors, far-UVC light could be used in combination with other measures, like wearing face masks and washing hands, to limit the transmission of SARS-CoV-2 and other viruses.”

The study is published in the journal Scientific Reports.

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By Chrissy Sexton, Earth.com Staff Writer