Stop the spread of COVID-19 by changing your light bulbs?
What if there was a magic device that could kill viruses like COVID-19 in the air and on surfaces? One that didn’t need disinfectant refills, and only took a small amount of power?
Turns out there is — it’s an ultraviolet lamp, specifically the UV-C spectrum. These lamps emit a high-energy, short wavelength light that disrupts DNA/RNA in microorganisms like viruses. The sun also emits this light, along with the better-known UV-A and UV-B, but the UV-C is absorbed by the atmosphere and doesn’t reach the Earth’s surface.
So why doesn’t everyone use it? Because UV-C light is “really nasty stuff — you shouldn’t be exposed to it.” UV-C burns human skin and damages eyes with only a few seconds of exposure. So, it’s used in hospital rooms, trains, AC units and drinking water, but only when people aren’t nearby. For example, NYC buses and subways are exposed to this light between the hours of 1am and 5am, and they need strict protocols to make sure people aren’t harmed while using them.
All this has been well known for 100 years. But in 2018 scientists at Columbia published a paper in Nature showing that the 222nm wavelength of UV-C light, known as “far UV-C”, still kills viruses but doesn’t damage skin and eyes. One of the scientists, David Brenner, gave a recent TED talk discussing the potential of using it in occupied areas to destroy viruses as they are shed. That seems pretty exciting — why hasn’t it gotten more attention?
Well, there are plenty of caveats. Here’s an excerpt from a report by the International Ultraviolet Association:
While initial findings are positive, further investigations are required on any secondary impacts of the technology when used in the presence of humans. For instance, the potential for unexpected photochemical reactions, e.g. in cosmetics or clothing; the potential for generation of ozone during continual operation or within enclosed spaces; and determination of threshold limit values (TLVs) for safe daily exposure are all topics that need to be better understood.
Think of the possibilities if these were solved: arenas could install UV-C lights for use during events, continuously disinfecting air and visible surfaces. The light is invisible, so dimly lit restaurants can use it to kill pathogens while patrons are enjoying romantic dinners. Depending on the safety findings, buildings could even replace existing light bulbs with LEDs that emit both visible light and UV-C, making constant disinfection quick and inexpensive to install.
My question is this: why isn’t there a Manhattan Project to develop this technology? Where’s the billionaire willing to take a chance on this? It may not work for a variety of reasons, but if it does, it has the potential to change everything — doesn’t it? For a fraction of the amount being spent on vaccines and tests, we could do the research to determine safety. As for the fact that the lamps are so expensive, we already have LEDs that provide UV-C light for portable sterilizers, why can’t we make them limited to the far UV-C spectrum and thus safe for human exposure? A physicist friend of mine suggested that it’s hard to get the precise wavelength right, but that just makes it more interesting.
There seem to be a number of promising areas for development of alternative, potentially cheaper and more efficient sources of far UV-C light. From a recent paper in ACS Nano:
The need for compact and efficient UV-C light sources clearly demands the investigation of alternative approaches besides traditional low-density discharge tubes, high-density plasmas, and the more recent LED devices. An alternative may be offered by relying on energetic free electrons as a source of excitation. Specifically, crystalline samples of hexagonal boron nitride (hBN) were shown to produce intense cathodoluminescence (CL) emission at a wavelength ∼215 nm upon bombardment by 20 keV electrons,86 which could even result in lasing when using an optical cavity. Initially thought to be associated with a direct band gap of this material, a subsequent study confirmed that the emission was related to the presence of an indirect band gap87 in which phonons provide the required momentum compensation during radiative de-excitation. This method was verified using field emission sources with electron energies down to 8 keV, which resulted in UV-C light generation at a wavelength of 225 nm from hBN powder,88 although the efficiency was <1%. Other materials with suitable band gaps may offer more efficient paths to UV-C light generation through similar incoherent CL processes.
This technology feels like it has the potential to help solve one of the world’s biggest challenges. I would love to be involved in a project that worked on the research and development to bring this to market. If you’re interested too, let me know.
