Scientists debate if UV light can slow spread of coronavirus

Some researchers are turning to the light — ultraviolet (UV) light, specifically — in the effort to slow the spread of the coronavirus.

It’s a century-old technology that has fought off other infectious diseases, even though President Trump was mocked earlier this year for suggesting it as a potential COVID-19 treatment.

Evidence shows that germ-killing UV light can inactivate airborne microbes that transmit tuberculosis, measles, influenza and SARS-CoV-1, the coronavirus responsible for the 2002-2003 SARS epidemic.

As COVID-19 cases surge and scientists express concern the novel coronavirus could be spread through the air, some hope that UV light could be used to disinfect high-risk indoor spaces and help slow the pandemic.

Researchers from Columbia University found that ultraviolet light at a certain wavelength killed more than 99% of seasonal coronaviruses present in airborne droplets.

“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 David Brenner, a radiation biophysics professor at Columbia and lead author of the study, which was published in the journal Nature last month.

The team is testing the effectiveness of the UVC light on airborne SARS-CoV-2, the virus that causes COVID-19, in a separate study. Preliminary data suggest that ultraviolet light is just as effective against the coronavirus.

UV light is being used to disinfect surfaces on public transit and in hospitals to decontaminate N95 masks for reuse, according to NPR.

Dr. William Schaffner, an infectious disease expert at Vanderbilt University, said the college’s medical center uses the technology for makeshift isolation rooms so that air from a room doesn’t contaminate hallways.

Some entrepreneurs, such as restaurant owners, have installed UV light technology to try to keep customers safe while operating their businesses.

Although some people are relying on UV light as a safety measure, Dr. Schaffner said the technology is geared to combat airborne spread, which he thinks is not a “noteworthy” means of transmission for the coronavirus.

“This is a technology designed to reduce airborne transmission, but if you don’t think airborne transmission is very important, why would you do this? Because it ain’t cheap. And it really does require constant maintenance in order to have them continue to be functional,” he said, adding that dusty lights can “markedly diminish” their effectiveness.

UV lights must be mounted high in a ceiling so that people do not look into the light, which can cause retinal damage, Dr. Schaffner said. And lights installed high in a ceiling will not stop the spread of the coronavirus via close contact of an infected person, he added.

However, there’s enough evidence to show that coronavirus aerosols can hang in the air and spread throughout a room so it’s time to take that airborne spread seriously, Richard Corsi, dean of Portland State University’s Maseeh College of Engineering and Computer Science, told NPR.

Mr. Corsi was one of 239 scientists who signed a recent letter calling for the World Health Organization to recognize the “significant potential” for airborne spread of the coronavirus and update its guidance.

In response, WHO has said airborne transmission is possible in some crowded, poorly ventilated areas, but maintained that is not how most infections spread.

Health authorities downplayed the risk of airborne transmission early in the pandemic, which “put the public at maybe a little bit too much ease” and people kept going to busy restaurants with poor ventilation, Mr. Corsi said.

While UV radiation in air handling units can be effective at decontaminating air that has passed through filters, Peter Raynor, an environmental health sciences professor at the University of Minnesota, questions the need for the technology if the filters are efficient enough.

“They are also expensive to install, so my take is that it might be better to use limited resources to accept higher volumes of outside air versus recirculated air, to install higher efficiency filters, and even to purchase and install higher capacity fans and/or fan motors,” Mr. Raynor said.