Right, I will readily believe that for many people with good glove hygiene, it is better to wear gloves than not. But if we're talking about irradiation that encourages everybody to cover up, that's a different question, especially since many people don't own single-use gloves. Would universal use of gloves make spread better or worse? It seems like most experts say worse.
Also, on the question of whether gloves prevent a person from touching their face, it probably can be helpful for some people, but that doesn't mean that it's helpful overall. From the same NPR piece:
But perhaps wearing gloves would keep you from touching your face? Nope, says Landon. "We see people touch their face all the time with gloves on in the hospital."
Adalja concurs. People wearing gloves still want to itch their faces, still want to adjust their glasses. "I know for one that when I'm wearing gloves, I do have a tendency to try to touch my face," he says.
The germicidal flux from the paper is 155.8 mW/cm^2, which is much stronger than sunlight which is about 0.1 mW/cm^2/nm at sea level for short wavelength visible light. I don't know what your threshold for alarming is, but to me that seems high enough that concern is warranted. And I'm not sure that conventional sunscreen would actually help. Based on this overview of sunscreen, it looks like most broad spectrum sunscreens don't do much above 380 nm or so.
Also, It doesn't seem clear to me that the fact that blue light is visible implies it's not harmful. (UV is harmful, and some species of bird and rodent can... (read more)
It's germicidal by an oxidative stress mechanism, so we should expect it to be carcinogenic (via the indirect DNA damage mechanism), at least at germicidal intensities (normal everyday exposure may be harmless to the skin, I don't know).
Wow, I would not have guessed that light within the visible spectrum would have any germicidal action at all (looks like 405 nm light is germicidal at fluences about 10,000 times as high as germidal UVC).
This brings up an important point which is that sunlight (UVA, UVB, and apparently visible blue-violet too) is somewhat germicidal, and open air treatment during the Spanish Flu had positive patient outcomes, as well as less spread, with nurses and doctors less likely to become infected.
This is exactly the sort of concern that needs to be more rigorously addressed before a solution like widespread far-UVC is implemented.
Agreed that some sort of prioritization of the public spaces most in need of sanitization would be good. The threshold for safety should be lower in cases where the potential benefit is high (and I didn't mention this in the post because it's highly speculative, but I suspect that shorter term occasional exposure may be much safer than constant exposure). Making such a priority list should involve empirical evidence. I agree that airplanes seem like a likely culprit given what we know about mechanism of spread, but it would be good to confirm this intuition with actual infection data (maybe this has already been done?). Given the... (read 385 more words →)
I spent a while looking into safety for this idea, and far-UVC has a ways to go before it's established safe enough for public settings---it's only been shown to be non-carcinogenic for one of two relevant DNA damage mechanisms. I've posted a more in depth discussion here.
Also posted on my personal blog.
Tl;dr: Far-ultraviolet light has potential as a human-safe germicide, but its safety is not established. In particular, evidence that it is not carcinogenic exists for only one of two mechanisms for ultraviolet carcinogenicity. In addition, use of far-ultraviolet light in public spaces to prevent the spread of SARS-COV-2 or other pathogens leads to a host of other concerns that need to be addressed.
In 2017, Nature published a paper that investigated the possibility of using far-UVC light to combat a future influenza pandemic. The paper went mostly unnoticed by non-academics, as is the norm for technical journals, but now with the novel coronavirus and... (read 3449 more words →)
To be clear, those two units are different. 155.8 mW/cm^2, and 0.1 mW/cm^2/nm. So it's not 1,558 times stronger than sunlight overall. Neglecting atmospheric effects, sunlight across all wavelengths is 135 mW/cm^2, so about the same total flux---it's like we compressed the broad spectrum of sunlight to all be a single wavelength. My point is that it's much much more blue-violet light (not much much more light total) than what we usually encounter. Blue-violet from sunlight may be safe for our skin, but that doesn't necessarily imply that blue-violet light at germicidal intensity is safe.
... (read more)