Tokyo — New lighting technology being pioneered in the U.S. and Japan may help to make riding the subway, going to school or moving through other public spaces as safe as a walk around the living room, despite the threat of coronaviruses and other pathogens.

The idea is to suffuse indoor areas with continuous, low doses of short-wavelength ultraviolet light. As anyone who’s had a sunburn knows, conventional UV light exposure is hazardous to humans, including the UVA light from the sun and UCV light currently used to kill pathogens. Both cause skin cancer and eye damage. 

But a growing body of research shows ultraviolet light at the far end of the light spectrum — “Far-UVC” — hits the sweet spot: It’s harmless to humans but still lethal enough to disarm bacteria, viruses and other disease-causing microorganisms.

The technology was developed at Columbia University’s Center for Radiological Research under physicist David Brenner, who calls Far-UVC a potential “game-changer.”

Far-UVC light “kills pathogens in the air before we can breathe them in,” he told a university magazine. Brenner’s team found Far-UVC wiped out coronaviruses responsible for coughs and colds, and it’s assumed to be equally effective at liquidating the virus that causes COVID-19.

Evidence for the safety of Far-UVC (222 nanometers on the light spectrum) was found in a study on mice published recently by Japan’s Kobe University. The team said its research — using mice modified to be more sensitive to UV damage — “provided proof for the first time in the world that direct and repetitive illumination from 222nm ultraviolet radiation… does not cause skin cancer.”

The scientists foresee wide-ranging applications in the real world, including for hand disinfection, in schools, food-preparation facilities and public restrooms.

The idea of using UV light to zap microbes is hardly new — the germicidal properties of sunlight, “nature’s disinfectant,” were established in 1877 when a pair of British researchers found that bathing bacteria-filled test tubes in sunlight extinguished the microbes.  Starting in the 1930s, a Harvard sanitary engineer demonstrated that UV lamps installed near the ceilings of public schoolrooms dramatically cut measles infection rates among pupils. 

UV light disinfects by scrambling the microbe’s genetic code, making it impossible for the pathogens to reproduce and infect humans. 

With the rise of antibiotics, starting in the late 1940s, UV light took a back seat in infection control efforts — until a few decades later, with the rise of drug-resistant “superbugs.” 

That’s what made it personal for Professor Brenner, who took on Far-UVC research after losing a friend to hospital-acquired infection.

With drug-resistant pathogens already killing more than 35,000 Americans every year, and on track to kill 10 million people worldwide by 2050, interest has resurged in UV germicidal lighting. 

“We actually know how to kill every kind of microbe, every kind of virus, every kind of bacteria, with UV light,” said Brenner.

“Primitive” UV use

Ultraviolet light is of shorter (10-400 nanometers) wavelength than visible light and infrared. 254nm is the long-time standard for germicidal light fixtures. UV germicidal light can kill pathogens that have evolved to be drug-resistant as easily as it can vanquish conventional microbes, and is already used to sterilize surgical theaters, research labs, HVAC ducts and in the semiconductor and food industries.

Recently, New York began testing UVC irradiation on subway cars and buses. A bus company in Shanghai is also using the technology, and says disinfection time has been reduced from 40 minutes to 5, with less labor to boot.

A company in Los Angeles sells a disinfecting device that can be pushed like a refreshment cart through airplane cabin aisles, and Boeing is working on a self-cleaning airplane bathroom that kills germs with a flash of UV light.

But at 254nm, germicidal UVC light can only be deployed when rooms are unoccupied. Japanese lighting manufacturer Ushio calls that “primitive” uses. A common sight in Japan, for instance, where patients often remove their shoes to enter the doctor’s office, are machines that dispense freshly UV-sterilized slippers. 

A lower-spectrum future?

A major player in the emerging Far-UVC 222nm disinfectant business, Ushio was founded in 1964 and makes everything from stage lighting and halogen fish-luring lights to laser diodes for the medical field. The firm licensed Columbia University’s technology in 2015, but had been selling 222nm lights since 1992.

With the onset of COVID-19, Ushio has accelerated its timetable for a Far-UVC 222nm roll-out, and expects to start commercial production this fall of its 92 x 70-mm (about 3 x 4 inches) Far-UVC excimer lamp kits.

Preliminary field-testing in hospitals has been promising. One Japanese doctor said wall-mounted Far-UVC lighting obviated the need to constantly wipe down doorknobs and other “high-touch” surfaces. Ushio says its product is intended for use in problem areas, like restrooms, production lines, and for hand hygiene. 

Brenner reckons Far-UVC will eventually become “ubiquitous” wherever large numbers of people congregate, but as he told CBSN earlier this year, “manufacturing is the main roadblock at this point,” along with the huge number of companies and organizations that may seek Far-UVC solutions.  

A Ushio spokesman said that, at least initially, high cost (he wouldn’t give an estimated price for the units) would likely limit the installation of Far-UVC units to places like airports, transit stations and hospitals.

And the concept isn’t perfect. One drawback to Far-UVC lighting is “shadowing;” environments with lots of nooks and crannies, such as car interiors, are difficult to disinfect thoroughly from wall- or ceiling-mounted light sources.

But given the enormous disruption and health repercussions of the COVID-19 pandemic — and the grim likelihood of more pathogen attacks in the future — UV light may well be poised to reclaim its front-line role in the fight against disease.