Could we stop flu outbreaks with UV light bulbs?
Shining a light on dangerous microbes
Public lighting — or a special kind of it — could be the next weapon in the war against the flu and other communicable diseases. A researcher from Columbia University in New York thinks that far-ultraviolet light could be an effective way of killing microbes — from drug-resistant bacteria in hospitals to flu bugs in public schools to world-travelling viruses in airplanes. "We can put these lamps in the ceilings of public places, so the air in that location will be exposed to these far-UVC rays, so any bacteria or viruses should be killed," said David J Brenner.
Ultraviolet light has been known to kill viruses and bacteria for about a century — and is often used to sterilize unoccupied spaces and medical instruments in hospitals. But too much exposure to regular UV light is dangerous for humans because it can penetrate into tissue, causing DNA damage and skin cancer, and damaging the eyes. Brenner, the director at the Center for Radiological Research and a professor of Radiation Biophysics at Columbia University Medical Center, thought there was a way around this problem. "We wanted to use the killing power of ultraviolet light, but we wanted to use it safely." So instead of using UVA and UVB light, that we try to protect ourselves against with hats, sunglasses and sunscreens, he's been investigating something called far-UVC light.
Far-UVC light has a very short wavelength — around 220 nanometers — which means it can't get at vulnerable human tissue. "From the point of view of safety," says Brenner, "far-UVC light simply can't penetrate the dead cell layer at the surface of our skin, and can't penetrate the tear layer at the very surface of our eye to get to the living eye." Viruses and bacteria, however, are far smaller and don't have any protective layers, so the far UVC light can penetrate their surfaces, and kill them by damaging their DNA.
Safe for people, deadly for microbes
That, at least, was the theory predicted by physics, says Brenner. But he and his colleagues have spent years testing the idea to make sure that far-UVC was safe for humans, and effective in killing microbes. Their safety testing, on lab-grown human skin samples and also on hairless mice, has found no evidence of any damage from far-UVC light.
The team has also been pleased with the effectiveness of far-UVC in killing microbes. One of their earliest trials was a test against MRSA — the "superbug" that's become a plague in hospitals. This was an early priority for Brenner, because part of the inspiration for the idea was the loss of one of his friends to a MRSA infection after minor surgery several years ago. In the MRSA experiment, they tested far-UVC light against conventional germicidal light. "Both types of light killed the MRSA cells just as well as one another," says Brenner. This, he thinks, suggests that far-UVC could be used during surgery to protect patients from being colonized by drug-resistant superbugs.
A more recent success was reported in a paper published earlier this month. The team tested far-UVC against flu virus carried on aerosol particles - the kind that infected people cough and breathing into the air. "This was our first where we were exposing influenza in a real life situation." Again, they found the far-UVC efficiently killed the viral particles being carried in air.
Preventing epidemics with UV light in public spaces
It will take a few more years of testing, but Brenner suggests eventually this could be deployed in a range of places where at-risk populations might be effectively protected, including hospitals, old-age homes, and schools. Far-UVC lights could be incorporated into regular public lighting, adding a public health benefit to standard illumination. He's particularly interested in the possibility of using far-UVC in airports. "If we could have these devices in airports and potentially in airplanes, perhaps we could prevent the spread of these pandemic flu epidemics from country to country."
One barrier in the short term might be cost. The far-UVC lamps that Brenner uses in his lab cost about $1000 US each. But he thinks that once a wider market for these specialty devices develops, the cost could drop significantly.