May be we should add to the discussion the description of the public spaces where UVC is needed.
First, planes. People risk infection in planes and they will not return to flying until planes will be made safer. If inside the planes will be sources of far-UVC—AND people will mandatory wear gloves, glasses and masks inside a plane, – where will no skin exposure and no cancer risk (above radiation levels which already happens to be in planes because of higher altitudes.)
More generally, small cancer risk from UVC may be net beneficial, as it would press people to wear gloves, masks and googles, and it will be the biggest contribution to the reduction of infection transmission.
Returning to public spaces. Next is taxicabs. Obviously, the driver should be separated form the passengers (and even replaced with autopilot). But the surface and air need cleaning after each passenger. Here the UVC will help again, but it will turn on only between the passengers rides.
Finally, elevators. The same way, they will be cleaned while idle.
Remember that airplanes and taxis have lots of shadowed places. Elevators less so, so I’d expect that to work better. Sticking a UV lamp in a plane’s ventilation (away from people) might help quite a bit, though.
People commonly reach into the little pockets behind seats for the in-flight magazines/barf bags/headphones/etc. People commonly secure things under their seats or in the luggage compartments. Armrests and seatbelts are commonly used for the stated purpose, and their geometry makes UV sterilization rather complicated. You may be underestimating the practical issues.
If you’re mainly concerned about viruses in the air, ventilation is probably a better solution (while the plane is unoccupied on the ground).
On Air vs Fomites: for this virus, a picture is emerging that fomites are basically irrelevant and air transmission via droplets or aerosols is what matters. But in general, there may be other pathogens where fomites are most important, e.g. norovirus and the like that spread via the fecal-oral route.
UV light can help with fomites but a full solution to fomite problems requires other changes, such as copper surfaces, better ways of making large amounts of very hygienic food, etc.
On ventilation: ventilation won’t eliminate droplets from sick people, it will dilute them somewhat over time. Airplanes already have ventilation via a compressor.
Far-UVC can zap droplets that are in the air before they get from person A to person B, which I think is the big win here.
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 way some countries are closely tracking infections, a data-driven understanding of which types public spaces would benefit most seems very feasible.
Additionally, as you mentioned, germicidal UVC (far-UVC or the conventional spectrum) could be used in public spaces when no humans are present. Of course there would still be some risk, because there will inevitably be some degree of error when it comes to turning UVC lamps on and off, but if implemented carefully, such risk could be negligible.
Regarding the idea that cancer risk could be beneficial, this seems doubtful to me. I don’t know much about gloves, but my understanding is that they don’t protect much if at all from coronavirus. The virus doesn’t pass through the skin, so there’s no obvious reason to prefer to have it on gloves than directly on your hands—germ covered gloves are no better for preventing spread than germ covered hands. And skin as a surface has evolved to be pretty good at dispelling pathogens, so cleaning your hands is actually easier than cleaning gloves. From an NPR FAQ:
Using your ungloved hands – and then washing them often – is the best bet for the typical tasks of everyday life.
“Skin is really great because it’s like a hydrophobic covering, which means it’s kind of waxy and sort of repels moisture,” explains Dr. Emily Landon, hospital epidemiologist and infectious diseases specialist at University of Chicago Medicine. “That means when you touch things, they sort of stay on your hands and then you can wash your hands and get rid of them.”
Wearing gloves might cause you to practice worse hand hygiene because you keep wearing the now-dirty gloves instead of washing your hands, Landon says. Gloves are only useful when you use them the right way and in a meaningful way.
In hospitals, for example, gloves are used for certain purposes and disposed immediately afterward. “We put them on what we’re going to do a task where we might touch something that’s going to be wet or icky or contaminated,” Landon says. “Then we take them off right away and leave them in the area with contamination and then clean our hands. Because it turns out more than 10-to-15% of the time, people who take off their gloves actually contaminate their hands with whatever was on the gloves.”
Plus forcing people to be completely covered up to avoid skin cancer would be quite a burden, at least in some cultures and climates. I know I would have trouble finding comfortable clothes that would keep all of my skin safe from carcinogenic rays.
Yes, the experiments are needed. The main benefit of gloves is that they prevent a person from touching ones’ face. If I go outside, I use onetime gloves and clean my hands on return.
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.
A joke: so the best way for air travel would be transport sedated people in boxes.
No joke: The plane crew could provide gloves to people inside a plane. This one-time gloves could be covered with virus killing material like coper, which will also protect against UV.
May be we should add to the discussion the description of the public spaces where UVC is needed.
First, planes. People risk infection in planes and they will not return to flying until planes will be made safer. If inside the planes will be sources of far-UVC—AND people will mandatory wear gloves, glasses and masks inside a plane, – where will no skin exposure and no cancer risk (above radiation levels which already happens to be in planes because of higher altitudes.)
More generally, small cancer risk from UVC may be net beneficial, as it would press people to wear gloves, masks and googles, and it will be the biggest contribution to the reduction of infection transmission.
Returning to public spaces. Next is taxicabs. Obviously, the driver should be separated form the passengers (and even replaced with autopilot). But the surface and air need cleaning after each passenger. Here the UVC will help again, but it will turn on only between the passengers rides.
Finally, elevators. The same way, they will be cleaned while idle.
Remember that airplanes and taxis have lots of shadowed places. Elevators less so, so I’d expect that to work better. Sticking a UV lamp in a plane’s ventilation (away from people) might help quite a bit, though.
The shadowed spaces probably don’t matter.
The volume of air you are trying to sterilize is the region around people’s heads, and to a lesser extent the surfaces that people touch a lot.
People commonly reach into the little pockets behind seats for the in-flight magazines/barf bags/headphones/etc. People commonly secure things under their seats or in the luggage compartments. Armrests and seatbelts are commonly used for the stated purpose, and their geometry makes UV sterilization rather complicated. You may be underestimating the practical issues.
If you’re mainly concerned about viruses in the air, ventilation is probably a better solution (while the plane is unoccupied on the ground).
On Air vs Fomites: for this virus, a picture is emerging that fomites are basically irrelevant and air transmission via droplets or aerosols is what matters. But in general, there may be other pathogens where fomites are most important, e.g. norovirus and the like that spread via the fecal-oral route.
UV light can help with fomites but a full solution to fomite problems requires other changes, such as copper surfaces, better ways of making large amounts of very hygienic food, etc.
On ventilation: ventilation won’t eliminate droplets from sick people, it will dilute them somewhat over time. Airplanes already have ventilation via a compressor.
Far-UVC can zap droplets that are in the air before they get from person A to person B, which I think is the big win here.
Strip-like sources of light and light sources beneath seats could partly solve this problem.
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 way some countries are closely tracking infections, a data-driven understanding of which types public spaces would benefit most seems very feasible.
Additionally, as you mentioned, germicidal UVC (far-UVC or the conventional spectrum) could be used in public spaces when no humans are present. Of course there would still be some risk, because there will inevitably be some degree of error when it comes to turning UVC lamps on and off, but if implemented carefully, such risk could be negligible.
Regarding the idea that cancer risk could be beneficial, this seems doubtful to me. I don’t know much about gloves, but my understanding is that they don’t protect much if at all from coronavirus. The virus doesn’t pass through the skin, so there’s no obvious reason to prefer to have it on gloves than directly on your hands—germ covered gloves are no better for preventing spread than germ covered hands. And skin as a surface has evolved to be pretty good at dispelling pathogens, so cleaning your hands is actually easier than cleaning gloves. From an NPR FAQ:
Plus forcing people to be completely covered up to avoid skin cancer would be quite a burden, at least in some cultures and climates. I know I would have trouble finding comfortable clothes that would keep all of my skin safe from carcinogenic rays.
Yes, the experiments are needed. The main benefit of gloves is that they prevent a person from touching ones’ face. If I go outside, I use onetime gloves and clean my hands on return.
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:
A joke: so the best way for air travel would be transport sedated people in boxes.
No joke: The plane crew could provide gloves to people inside a plane. This one-time gloves could be covered with virus killing material like coper, which will also protect against UV.