MIT researchers say you're no safer from Covid indoors at 6 feet or 60 feet in new study challenging

[SheltieLover]

https://www.cnbc.com/amp/2021/04/23/mit-researchers-say-youre-no-safer-from-covid-indoors-at-6-feet-or-60-feet-in-new-study.html

The risk of being exposed to Covid-19 indoors is as great at 60 feet as it is at 6 feet — even when wearing a mask, according to a new study by Massachusetts Institute of Technology researchers who challenge social distancing guidelines adopted across the world.

MIT professors Martin Bazant, who teaches chemical engineering and applied mathematics, and John Bush, who teaches applied mathematics, developed a method of calculating exposure risk to Covid-19 in an indoor setting that factors in a variety of issues that could affect transmission, including the amount of time spent inside, air filtration and circulation, immunization, variant strains, mask use and even respiratory activity such as breathing, eating, speaking or singing.

Bazant and Bush question long-held Covid-19 guidelines from the Centers for Disease Control and Prevention and World Health Organization in a peer-reviewed study published earlier this week in Proceedings of the National Academy of Science of the United States of America.

"We argue there really isn't much of a benefit to the six-foot rule, especially when people are wearing masks," Bazant said. "It really has no physical basis because the air a person is breathing while wearing a mask tends to rise and comes down elsewhere in the room so you're more exposed to the average background than you are to a person at a distance."

More at link.

[gratuitous]

1. Chemical engineering, and applied mathematics

Thank you for your contribution, gentlemen. Do you mind if we continue to listen to the public health professionals and other trained medical persons?

[ProfessorGAC]

2. Actually, Many Chem Es...

...with advanced degrees are highly expert in fluid dynamics & diffusion effects.
That said, i also question their outcomes.

[dsc]

3. actually both of those fields would be fairly well versed in how air flows which appears to be what

is being discussed.

[caraher]

22. These people have more expertise on how fluids and droplets move than medical people

This is an expert contribution to the study of how to keep safe. No single discipline has a monopoly on information relevant to battling this pandemic.

[dalton99a]

4. "Fauci is such an idiot, he should have used the Bazant & Bush risk calculator"

[marie999]

21. Thank you for making it easier to understand.

Just kidding.

[TheRealNorth]

5. What I don't see is...

Last edited Fri Apr 23, 2021, 02:51 PM - Edit history (2)

Did they look at and measure virus transmission at 2 feet or 3 feet, or just 6 feet? The reason the WHO/CDC says 6 feet is precisely because respiratory droplets don't tend to stay in the air past 6 feet. I mean, the statement that being at 6 feet is as safe as 60 feet is a "well, duh" kind of statement.

Also, the reporter implying that this should be used to loosen restrictions on indoor business provided masks are worn kind of ignores the fact that if there is eating or drinking, then masks are not being worn.

Seriously. Did the Restaurant and bar industry pay for the research?

[ananda]

20. Yes, it does sound fishy.

Masking and distancing work.

Period.

[JCMach1]

34. Never bought 6ft. A Korean researcher early on in the pandemic

Was pointing to as far as 18ft. ... I am sure certain environments, activities, etc. Could possibly spread it farther.

[soothsayer]

6. How about some actual experiments? Did they do those, or just theorize?

Theories are of course fine but seems to me you could measure this kind of thing.

[IrishAfricanAmerican]

7. Wonderful, more fuel for the lunatic's conspiracy theories!

I'm sure the Russian troll farms will be right on this.

[Hugh_Lebowski]

8. How about 6 feet versus 1 or 2 feet? Since that's the ACTUAL POINT of the 6ft rule

Seems like that's the more pertinent comparison.

All in all, from what's being said here, sort of implies you can't safely be indoors with someone who's infected unless they're REALLY far from you.

Am I understanding that correctly?

[elias7]

11. I think the 6' rule comes from droplet precautions

in the droplets travel up to 6 ft from a cough before they fall to the ground. My sense from the start was that it has the contagiousness more suggesting aerosolized transmission, not as readily transmitted as measles, but more so than influenza.

[Hugh_Lebowski]

15. Okay but ...

The probability of getting sick from another sick person has a lot to do with the quantity of the germ that is introduced to your system, right? The 'load'?

Given this, it's simply not physically possible that standing X feet from a sick person is not more dangerous than standing X+Y feet from a sick person (where Y is positive number), due to simple concentration differences. The greater the distance, the more dilute and hence less potent the 'load'.

You might be just as likely to 'get some on you' from background levels in the environment, but that's different from getting sick from what you get on you/in you.

If it is actually true that you're as likely to get sick by being 6 feet as from being 2 feet, and 6 feet is the same as 60, basically the inevitable conclusion is that people really shouldn't be in enclosed public spaces at all, period.

Basically if these researchers are using these measurements to show how we should be opening everything up, raise capacities, and not worry about our distance from each other I have to wonder who's money are they taking? Because it seems to me, unless I'm missing something, that this research means the opposite of that.

More likely however ... the problem is the writer of this article not grasping what they're reading.

[Sgent]

26. Meh

After about 1 meter or so it doesn't make a huge difference. Think of second hand cigarette smoke indoors, unless they are blowing it directly in your face it diffuses quickly.

[joetheman]

9. Has anyone ever seen the aerosol results of a sneeze? Of had a person sneeze in an about

10 feet away in an enclosed 12 x 12 room? If you have, then you know distancing is important as well as masking. Life experiences ought to teach us something. I have literally felt the spray from a sneeze about 10 feet away in an enclosed room and it depends on the force of the sneeze.

[SWBTATTReg]

10. If is was 60 feet spacing that was needed then wouldn't everyone be sick now?

I question that the real world application of mathematics can accurately depict the spread or contagion components of Covid 19.

I would suspect that over increasingly longer distances, that the number of airborne viruses drop in quantity as the distance traveled increases. Makes sense as heavier particles fall to the ground closer in, and lighter particles travel further (but do fall to the ground eventually). IMHO.

What gets me is that w/ those practicing safe distances of 6 feet (recommended) vs. 60 feet (a ridiculous distance) and masks, why has infection rates fallen still, w/ the 6 foot separation?

[underpants]

12. Well then I'm staying at least 60 feet from everyone at MIT

Knowledge is good. Thanks MIT.

[Pobeka]

13. I quickly reviewed the actual paper (not the cnbc unscientific analysis).

Lots of "we estimated this", "we estimated that". No mention of "we measured this" (though I may have missed it). If your model is built with estimates, it is only as good as your estimates.

The other problems with models, is the phenomena of predicting average results, rather than a range of results. So while the average may never predict a viral load necessary to cause and infection, in reality such a viral load that is above average will happen some of the time, and viral loads lower than average will happen some of the time.

https://www.pnas.org/content/118/17/e2018995118

[caraher]

23. Yes, it's a model

But it's a model that is clear about its inputs, and what I like best is that the supplementary materials include a spreadsheet you can use to enter your own parameters.

Subject to your caveats about averages, etc. I think they've developed a useful tool for assessing particular spaces and the potential impacts of various interventions. It's instructive, for instance, to play with the mask effectiveness parameter; this has an enormous effect on the calculations.

[ProfessorGAC]

28. Another Thing That Bugged Me

Their well-mixed room insistence. They included occupancy as a variable. They rightly added flow properties for movement, inhalation/exhalation of the occupants, etc. But, if the room is occupied, then one has to assume a single point source of contamination. That makes no sense, as those closest to the point source would get the load before flow properties & diffusion have to distribute any contaminant.
Also, they insist on well mixed but everyone has experienced being near the source of in-flow (a draft) or being in the far inside corner of a room.
Given the laminar flow along the walls & flow, and u changing as one moves away from the source of motion (a measure of turbulence, which is not linear to volume) I think they overstate the quality of mixing.
Lastly, a factor missing in their occupancy (admittedly I'm running on a tablet & can't open the XL model) is surface.
At various degrees of occupancy, layers and composition of clothing has and effect as fabrics can hold viruses as particles.
Add to all that, it is simply illogical to ignore volumetric change in concentration. They cover that, but I don't agree with their premise of the well mixed system.
Other than that, I think it's great. If by great I mean scaremongering with models that fly in the face of actual data.

[Pobeka]

29. Yep, when I think about the reality of air flows in a room.

From HVAC, and importantly the viral sources -- our mouths, our different lung capacities, coughing, laughing, talking (I know some people who are almost literal spitters when they talk, you can see it in sunlight). All these folks moving their heads in different directions. The actual variability of "receivers" of exhalation streams seems to be quite specific.

If you are sitting across from an infected individual who is talking directly at you, absent uncomfortable amounts of airflow, you are getting a heavy concentration of that person's exhalations and whatever viral load is being shed. All the other people in the room may get something that is more like "well mixed".

I suspect those direct interactions are the ones that really count in terms of a new infection occuring. No one, in any situation in the room, is actually experiencing well mixed, it's just illogical to me.

[ProfessorGAC]

32. I've Been Involved In Several...

...complicated mixing studies, mostly 2 phase (liquid/liquid & gas/liquid) while identifying issues with scale-up failing to meet kinetics.
It's actually pretty hard to get a well-mixed system. It's not something that just conveniently happens absent very long intervals. (If at all in a 2 phase system, and we're talking gas/liquid or gas/solid here.)
That's stuck in my throat regarding this report.

[myccrider]

35. I wondered about that, too.

Not any kind of expert, seriously not, but a bunch of people in a room are going to prevent a well-mixed situation. Unless they are all sitting still, breathing at the same rate, with no one speaking, coughing, sneezing, no doors opening/closing, no HVAC turning off/on, etc for extended periods of time, then the mix will be disturbed.

The mix of virus would change as soon as an infected person talked, sneezed, coughed - even with a mask. If you’re sitting 1 foot from that person, even masked, you will get more viral load than someone sitting 6 feet away. The mask may prevent you from getting infected but you still had more exposure. If you continue being repeatedly exposed at that close range, your chances of catching the virus go way up.

A mask helps prevent virus spread but is not some absolute barrier. If you were in a closed room with a large viral load for an extended period of time, the mask would probably become less and less protective, imo. That’s why, iirc, it was determined that walking into a grocery store to shop and then leaving was less dangerous than being a check out clerk in the same store, exposed all shift, even if everyone was masked.

So, yeah, I agree. What the study tells me is that you don’t want to spend a lot of time in an enclosed space with other people, even if everyone is masked. Having the virus evenly spread around a room doesn’t encourage me to go into that room!

[Pobeka]

31. See my post #30. n/t

[TheRealNorth]

14. After skimming the article....

I think the reporter may be either mischaracterizing the study or just doesn't understand it. What I think the authors were really looking at was risk of airborne transmission beyond 6 feet, not droplet transmission. Basically, they are saying that the 6 foot rule doesn't do much good for airborne transmission (again, this is already known) and offers a model that can be used to reduce the risk of AIRBORNE transmission in enclosed spaces. And that model certainly has value if verifiable.

Now there is some disagreement of the nature of Covid-19 transmission - whether if its strictly droplet or if airborne transmission commonly occurs. The author of the journal article s actually arguing that 6 feet rule is insufficient for preventing airborne transmission (which is what we would expect since the 6-foot rule is based on the preventing infection via droplets).

I really think this is either a poor job of reporting by CNBC (or misleading).

[Hugh_Lebowski]

16. If it's a poor reading I expect the authors to raise hell and demand it's taken down

Anything less is unscrupulous.

[roamer65]

17. Makes sense in a closed circulation environment.

Eventually an infected person will bring the concentration up to level where most others in room can be infected.

It just depends how long they are present in the room, and viral load they are ejecting.

There is a solution.

GET VACCINATED.

[Kid Berwyn]

18. Even Dumpy knew. He just didn't share.

“PRESIDENT” DONALD TRUMP: It goes through air, Bob. That's always tougher than the touch. You know, the touch - you don't have to touch things, right? But the air, you just breathe the air. That's how it's passed. And so that's a very tricky one. That's a very delicate one. It's also more deadly than your - you know, your - even your strenuous flus.

https://www.npr.org/2020/09/10/911368698/trump-tells-woodward-he-deliberately-downplayed-coronavirus-threat

[brewens]

19. I was glad to see the 6 ft indoors recommendation and hoped it would be okay, but I wasn't

about to trust it. I have only been in public buildings four times since October, and two of those were my vaccinations. The other two were a pharmacy and emergency plumbing parts. I'm still laying low until I'm certain the risk is real low.

[harumph]

24. I'd tend to trust epidemiologists and immunologists more than chemical engineers

For example, what is the half life of viral viability in the air?

[DontBelieveEastisEas]

25. concentration in the turbulent jet at a distance of 6 ft is 30 times higher

Last edited Fri Apr 23, 2021, 06:45 PM - Edit history (1)

From the article.
"We next consider the worst-case scenario governed by the Six-Foot Rule, in which a susceptible person is directly in the path of an infected turbulent jet at a distance of 6 ft, over which the jet is diluted by a factor of 3% (43). The associated concentration in the jet is still roughly 30 times higher than the steady-state concentration in the well-mixed ambient (when fd=0.001), and so would result in a commensurate amplification of the transmission probability."

Their point is more with masks and also with a well-mixed (air) room.

Also, I didn't see that the risk isn't just as great in at 1,000 feet

But this is probably just just aerosol risk not large droplet.

These articles seem to often have sensational phrases that paraphrase what the research/researchers said, but not accurately.
you're no safer from COVID indoors at 6 feet or 60 feet
^ I'll bet that is not in the real research paper and I'll bet that the researchers didn't say it without qualifications. That is just the journalist.


Like on CNN lately when it said something like, disinfecting surfaces was "all for show".
That was not true according to the real research.

[Klaralven]

27. Distance should tend to dilute the airborne cloud; drying should make the particles less infectious

Air near a person talking, laughing, shouting would have more viral particles per liter than air far away. And it will be more concentrated that the long term average in the room if there is reasonable ventilation and air exchange with the outside.

Also, the longer a viral particle is suspended in the air, the more it will dry out, which may affect infectiousness.

I haven't seen a good analysis of infectiousness versus dose of viral particles or whether the illness is more severe if it is the result of a larger viral dose. But I'd conjecture that dose matters.

[Pobeka]

30. ANALYSIS IS FOR MASKED PEOPLE: From the author's appendix, some critical info not in the cnbc piece:

Last edited Sat Apr 24, 2021, 09:19 AM - Edit history (1)

G. Disclaimer. Our Indoor Safety Guideline calculator is an
evolving tool intended to familiarize the interested user with
the factors influencing the risk of indoor airborne transmission
of COVID-19, and to assist in the quantitative assessment
of risk in various settings. We note that uncertainty in and
intrinsic variability of model parameters may lead to errors as
large as an order of magnitude, which may be compensated for
by choosing a sufficiently small risk tolerance. Our guideline
does not take into account short-range transmission through
respiratory jets, which may substantially elevate risk when
face masks are not being worn, in a manner discussed in the
main text. Use of the Indoor Safety Guideline is the sole
responsibility of the user. It is being made available without
guarantee or warranty of any kind. The authors do not accept
any liability from its use.
---

In other words, they made no attempt to model a situation where everyone in the room is not wearing a mask.

[Meowmee]

33. This is not believable to me

We have seen what covid 19 has done here due to lack of masks and lack of sd etc. We have seen what countries who had strict lock downs and who followed strict sd and masking have achieved. People spend way more than one minute in enclosed areas such as schools, restaurants business etc. These are the most common places where illness is spread as well as at medical facilities obviously. Having higher occupancy etc. and less distancing is not suddenly ok.