Japanese study shows face shields do not stop the spread of smaller airborne droplets

Earlier this week there were headlines about the fact that the CDC had removed, then replaced, coronavirus guidelines stating that the virus could be spread through airborne particles that hang in the air, not just droplets transmitted person to person. This would have huge implications on reopening guidelines, however we know that science does not matter to this administration. I heard a scientist on NPR say that in a normal administration, six months into a deadly pandemic, we would be getting daily briefings from the CDC. Of course this isn’t happening because Dear Leader wants to control the narrative. We’re now hearing that morale is of course low at the CDC and that staffers are frustrated by the fact that they’re being undermined by the administration and by senior CDC officials kowtowing to them. We’ve seen Republicans try to deny climate science for years, now that millions of lives are more immediately at stake how is it surprising that they’re not behaving any differently?

In another piece of news that is frustratingly not surprising, a Japanese study found that face shields don’t protect against the spread of coronavirus. Using a simulation with a supercomputer, they found that all smaller droplets escaped from people wearing a face shield. The shield only blocked half of the larger droplets.

Riken, a government-backed researcher center in Kobe, Japan, conducted the study by using Fugaku, the world’s fastest supercomputer, according to the New York Times and the Guardian.

Results from the study reportedly proved that nearly 100 percent of airborne droplets less than 5 micrometers in size escaped through the plastic shields. In addition, about half of larger droplets measuring 50 micrometers found their way into the air, the Guardian reported.

Makoto Tsubokura, a team leader at Riken, strongly recommended that regular face masks be used instead of plastic face shields for protection from the virus.

“Judging from the results of the simulation, unfortunately the effectiveness of face guards in preventing droplets from spreading from an infected person’s mouth is limited compared with masks,” he told the Guardian.

Tsubokura also said that those who have been advised to not wear face masks, such as people with respiratory issues or young children, can use face shields instead — but only outdoors or in properly ventilated indoor areas.

[From People]

I’d be curious to know if these shields actually prevent droplets from reaching the wearer. Like do they work for people wearing them, but not for everyone around them? I would assume they’re ineffective as personal protection too. I live in rural Virginia. The only people I see wearing face shields are workers, like at stores or during food pickup. I try not to go through their lines.

Very few non-workers are wearing shields, but I’d rather see someone with a shield than without a mask entirely. The shields do have eye protection when worn with masks, and may keep people from touching their faces. I think they should be used along with masks, and should not be allowed as alternatives to masks.

Incidentally, the study that supposedly showed that neck gaiters were worse than wearing no mask only tested one kind of gaiter in a very small study. Even the scientists said that the reports about it were inaccurate. It sounds like this study is much more reliable.

Also, face masks are truly effective and are helping not only stop the spread of coronavirus, but may decrease the severity of the virus for mask-wearers who get it. Kaiser pointed me to this Twitter thread (segment below) and article detailing a new opinion piece in the New England Journal of Medicine. Scientists theorize that masks may be “helping to reduce the severity of the virus and ensuring that a greater proportion of new infections are asymptomatic.” This is just a theory so far, based on the idea that exposure to a smaller viral load creates less severe symptoms, but it sounds so promising.



photos credit: Ian Panelo via Pexels and Julian Wan via Unsplash

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32 Responses to “Japanese study shows face shields do not stop the spread of smaller airborne droplets”

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  1. Case says:

    It hasn’t even dawned on me how little we’ve heard from the CDC recently in terms of briefings. That’s scary.

    I think if I absolutely had to travel or go to a crowded place, I’d wear a face shield in addition to my regular mask. I understand the shields are ineffective when it comes to droplets escaping the wearer, but I can’t help but think the additional protection would help some droplets from reaching the wearer.

    • Swack says:

      When I got my flu shot recently the person giving it wore both a mask and a guard. I assume the guard was to protect the eyes.

    • (TheOG) Jan90067 says:

      When I have to go to City of Hope Hospital for my blood work (every three months, as a Leukemia survivor), I wear a mask AND a face shield. It helps prevent any droplets from entering the eyes. So, yeah..it DOES help. But think about where you’re going and the protection you need. A face shield is IN ADDITION to a mask (the FIRST thing you should be wearing!).

  2. Sarah says:

    I’ve seen quite a lot of retail workers here in the UK (who until now were not required to wear masks) with face shields and it seemed so obvious that those things would do next to nothing to protect me from them (the point of masks) and not much to protect them from me if worn without a mask. The guidance was that they should be work with masks but a lot of people ignored this.

  3. Lexilla says:

    I have to believe wearing a mask and face shield is better than just a mask. My young daughter has a doctor’s appointment today and I’m having her do both.

    • Ripley says:

      I agree. Find myself wearing my glasses almost 100% of the time in hopes of protecting my eyes…. there was a (very small) study in China which found only 6% of the positive cases wore glasses on the regular. Meaning the 94% were sans glasses so I figure I will save money on contacts and wear my glasses.

    • Bros says:

      We took a vacation in july to mexico and wore both masks and face shields on the plane/airport.

      • (TheOG) Jan90067 says:

        I gave both my nephews (and their gfs) masks to wear in addition to their masks, when they flew back to school in August. It’s esp. important on a plane. WEAR PROTECTIVE GEAR PEOPLE!

  4. emmy says:

    That’s… logical? Did we need a study for it at this point? I guess for some people. I recently read an article in a large German newspaper that said the disposable masks worn in hospitals etc are better/more effective than cotton masks. I forgot why but I think it had to do with permeability. I feel bad re the environment but I’ll stick to those for the foreseeable future.

    • Diplomanatee says:

      I’Ve seen some health workers doubling up and wearing a washable cotton mask on top of the disposable one, so they can reuse it. Don’t know how good that is as the disposable one still gets humidity from one’s own breath.

    • (TheOG) Jan90067 says:

      Disposable masks DO GET PERMEATED. This is why you MUST throw them away after a certain amount of uses. They won’t stay effective forever.

  5. MaryContrary says:

    If I had to go on a plane (shudder) I’d wear an N95 and a face shield or goggles. But my husband (who is a scientist) has been saying the whole time that face shields on their own do not protect other people (same with the plexiglass dividers going up in classrooms). Aerosols travel.

    • Jenn says:

      Well said. I think people just WANT to believe that face shields alone will protect them — wishful thinking! — but we already know that they do not.

    • (TheOG) Jan90067 says:

      I personally find it so stupid, that stores put up those little 2-3 ft wide Plexiglas shields JUST on the counter. Like aerosols are JUST going to go forward and not up or around it. It’s just plain DUMB. Waste of money frankly. Just put it up ACROSS the ENTIRE counter. Sad, but it has to be like banks, with the people behind the counter completely protected.

  6. Mel M says:

    I was just ranting to my husband last night, per usual, about the CDC. They are literally the Centers for DISEASE CONTROL and they have been a failure with the deadliest disease of our lifetime. I have pretty much zero trust in them at this point because it’s quiet obvious they are not working to to help the American people.

    • MaryContrary says:

      It is so horrifying that they (and the FDA) are being pressured by the administration. They have always been apolitical-it’s yet another sign of how far our country has been brought to its knees by Trump.

  7. Gil says:

    This whole situation about the debate of wearing mask is still beyond me. I live in Tokyo and I have been witness of how people is adapting to the this new way of life. Children wearing mask at school, ladies chatting at the coffee shop while wearing masks, business meetings taking place with every member wearing a mask. It’s not that difficult, and it’s doable.

  8. erni says:

    I live in a 3rd world country. Even we know you need to still wear mask even though you already have face shield

  9. Peanutbuttr says:

    I thought face shields were supposed to be worn with masks not in place of them? My mother works in a mental health clinic and they gave her a shield that was supposed to be worn WITH a mask.

  10. Judith says:

    ” I think they should be used along with masks, and should not be allowed as alternatives to masks” agreed, but I have a small side note, I think as long as there are no alternatives for masks that would allow deaf or hard of hearing people to understand colleagues/contacts/essential workers they should still be allowed. It is already difficult enough for differently abled people to function in this society, without cutting off their means of communication with the rest of the world.

  11. souperkay says:

    Face shields also have to be worn correctly, straight across the forehead below the hairline and slightly above the eyebrows, with the length of the shield extending beyond the chin. They should only be used in conjunction with a cloth face mask, also worn correctly covering the nose and chin.

    Without a face mask, face shields do not offer enough protection to be worthwhile, and a correctly worn face mask is the best protection.

  12. Angela says:

    Um I saw this post and immediately thought no shit sherlock 😂😂

  13. Lala11_7 says:

    Face masks protect your EYES…as aerosol spray…which lingers like SMOKE…can infect you just as well as large droplets 💦 …and your eyes are a portal…just like your nose and mouth…If you’re in an enclosed space like a airplane…or old buildings like schools…etc…protect your EYES…like your nose and 👄 ❣❣❣

  14. Izzy says:

    I was always under the impression that a face shield was meant to help mitigate the amount of droplets making contact with the eyes, which do have mucus membranes. This is not considered a primary method of transmission, inhalation is much more a risk factor, so masks need to be worn regardless of a shield.

  15. Eenie Googles says:

    I knew without a study this because I looked at one with my eyes.

  16. heygingersnaps says:

    One of the local bakeries here have their staff wear a face shield in place of a mask even when people have kindly told them that it would hardly protect them without a mask but the owner is stubborn and says that they have done some assessments and face shields are enough. =/

  17. Jenn says:

    That Telegraph article is amazing. The theory is, if you’re wearing a mask and inhale an *inconsequential* “dose” of virus, this may in fact be the same thing as having a vaccination: a harmless dose is enough to create protective antibodies. More research is needed, but it’s promising!!

    Meanwhile, our underfunded CDC is a disaster. People struggle to adjust to new information and therefore believe the first thing they hear, and the CDC’s early pronouncement that masks are “ineffective” has directly contributed to countless deaths. (The CDC’s utter incoherence is by design, of course; this administration’s MO is the sowing of confusion. I don’t know what it would take to regain public trust.)

    Last night I listened to an NPR piece about location-based contact-tracing phone apps here in the U.S. — our best hope against this pandemic!! — and, specifically, about their woeful inadequacy as compared to the apps helping epidemiologists in other nations. Underfunded (each state is responsible for its own app), they aren’t consistent or even really supported, and as a result, they don’t work. So public trust erodes further, ensuring that people won’t use them. Again: a disaster.

    • K.T says:

      Thank you, Jenn! I read those articles and study too, and it’s hugely interesting that some research says that masks might be providing some for of inoculation or pre-vaccine shield for wearers! I mean, from March, many researchers were talking about ‘viral load’ and how it’s not just about getting COVID but how MUCH COVID virus received that affects the body’s reaction. That one infected cruise ship which wasn’t allowed to dock was used as an example in the study – it showed after 100% mandatory masking was implemented, 80% of those that still got COVID were asymptomatic and of the others that got COVID symptoms, they were very mild illness and no deaths.

      It really annoys me when people say “masks protect not the wearer, but only other’s…” Not true!! masks and social distancing and glasses etc. protects the wearer a lot!! If you’re unlucky enough to be in contact with coronavirus then it’s all about trying to lower the viral load you receive!!!

  18. Lissdogmom02 says:

    Our doctors wear these with masks & sometimes glasses as well. They alone are definitely not enough.

  19. Ana says:

    That’s why you wear a face shield plus a face mask. Duh

  20. Lex says:

    I wish the shields were more effective as they help deaf and hard of hearing people so very much, making them slightly less isolated in this tough time. Imagine relying on lip reading these days…