Ultraviolet light could disinfect scarce medical equipment


By Dennis Thompson

HealthDay Reporter

TUESDAY, April 28, 2020 (HealthDay News) – Supplies of personal protective equipment remain in short supply across the United States, especially the N95 respirators that healthcare workers use to protect themselves from the new coronavirus.

To help extend the life of available equipment, researchers and hospitals are turning to a known, though little-used, disinfection medium, ultraviolet radiation.

“In general, it is well known that UV-C radiation kills microbes,” said Bob Karlicek Jr., director of the Center for Lighting Systems and Applications at the Rensselaer Polytechnic Institute in Troy, New York. “What is not known is the specific amounts of UV-C radiation required to completely disinfect complex equipment such as N95 masks, because light has to be brought into the mask.”

Karlicek led a team that created a UV-C system designed to disinfect N95 masks. It is being tested at Mount Sinai Hospital in New York City.

President Donald Trump was ridiculed last week after publicly speculating that ultraviolet light could be used to treat COVID-19 infection within the human body.

“Suppose we hit the body with tremendous light, either ultraviolet or just very powerful, and I think you said it hasn’t been verified, but you’re going to prove it,” Trump said at a press conference. “And then I said, assuming you brought light into the body, what you can do through the skin or some other way, and I think you said you’re going to try that too. Sounds interesting.”

Experts quickly realized that UV light can be harmful to humans, and that it would be impossible for ultraviolet rays to reach deep into the body to kill the coronavirus in the lungs and other organs.

That’s also part of the problem with using UV light to disinfect protective equipment like masks, gowns, and gloves, Karlicek said.

UV light disinfects by breaking down the genetic makeup of coronaviruses and other microbes, he said. The virus dies or becomes unable to replicate.

But that means ultraviolet rays must directly attack the virus, which means that every square inch of equipment must be exposed to ultraviolet light to properly disinfect. Karlicek said that any part that remains within a shadow could still carry active coronavirus.


UV rays must also be very powerful. Mere sunlight alone will not kill the coronavirus, experts say.

The Rensselaer team solution is a conveyor system that runs N95 masks through a battery of mercury UV lights.

“That allows us to have a vertical arrangement of the UV-C mercury lamps and then carefully suspend the masks in a movable frame that would go between the lamps, so you can simultaneously radiate masks from both sides,” Karlicek said.

The system is approximately 8 feet tall and approximately 8 feet long. The masks are hung from a series of hooks, and the speed of the conveyor belt determines the amount of radiation the masks receive.

Mount Sinai doctors are testing the system to determine the exact level of UV exposure needed to completely disinfect the masks, Karlicek said.

“There is no doubt that we will be able to disable the virus with the correct dose,” he said. “The question is how many uses can we get? Does UV light damage the straps that hold the mask on my face? These are things that need to be resolved.”

Other groups are also trying to develop similar solutions. For example, a team from the University of California, Santa Barbara, is working on a system that would use LED lights to sterilize UV-C radiation protection equipment.

“Anything we can do to extend the life of N95 masks in particular, which are relatively rare almost everywhere, that’s certainly something I’d like to see developed,” said Dr. Matthew Heinz, a hospitalist and internist at Tucson. Arizona Medical Center.

“Of course, we have to take adequate precautions and make sure that we are properly sterilizing personal protective equipment,” he added.

Karlicek’s team assembled their prototype for about $ 10,000, but warned that supply problems would hinder efforts to make more light disinfecting machines.

“One of the biggest challenges we had in building the system was finding a supply of mercury lamps that were now available on the market, rather than being delayed for five to six weeks,” said Karlicek.


He noted that similar devices, such as wands, boxes, and bags, are now available to disinfect at home using UV light.

“People are selling UV-C disinfection systems for the home, particularly UV-C wands that you can move on surfaces,” Karlicek said, adding that he doesn’t consider them a good idea.

“You have no idea how much UV-C light you are getting from one of these wands, and you have no idea how to use it to get a proper dose,” he said of home users. “To disinfect well, you really need a good amount of UV-C light.”

These devices can also be dangerous to people. While UV-C light cannot penetrate the skin, it is bright enough to harm the eyes, Karlicek said.

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SOURCES: Bob Karlicek Jr., Ph.D., director, Center for Lighting Systems and Applications, Rensselaer Polytechnic Institute, Troy, N.Y .; Matthew Heinz, M.D., hospitalist / internist, Tucson Medical Center, Arizona

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