Pretty sure that's just the City of Los Angeles, not the county. I haven't been to any grocery stores outside DTLA that required masks. (though 7-11 did)
this is probably a little overly cautious relative to the actual reduction in risk (you'd have to be especially unlucky to get infected just from regular breathing in a grocery store), but not terribly unreasonable, particularly for those with co-morbidities.
but i routinely see people with masks and gloves on while walking outside. not shopping, or going to shop, just walking. it's so odd, and frankly, wasteful.
It seems that face masks are quite effective in reducing the spread of illness. For example, look at the numbers in South Korea, Japan, etc. (where mask-wearing is common) compared to ours. Masks don't need to do 100% of the job -- rather, we would hope that in combination with moderate social distancing, better hygiene, improved testing, etc. we could reduce the rate of transmission. If each infected person spreads the illness to an average of only 0.9 others, then it won't do much more damage.
Now, from an economic angle, the US government just passed a $2 trillion stimulus package, which works out to about $6,000 per American. There are calls to spend much more money. Suppose we spend 5% of this on face masks, so $300 per American.
Currently, face masks can be bought at $20 for a box of 50 on Amazon. That gets 750 face masks to every American, at a cost that is cheap relative to the other costs of Covid-19.
And this is ignoring economies of scale. If the government decided to distribute free face masks in every school, every restaurant, in every theater, etc., then it could produce them at much cheaper than 40 cents each.
All in all, it seems like a potentially good investment.
99% of the reduction in transmission comes from physical distancing alone while inside of closed spaces with strangers. hygiene is likely negligible outside of a very few high interaction zones inside those enclosed spaces. testing only improves targeting who to distance (isolate).
it's a virus that rides on tiny masses of water to hopefully jump into the nasopharyngeal cavity of the next host. if it doesn't make it to those warm and juicy brachiae, it exponentially decays to the elements in hours. relative to air, those virus-laden water masses are heavy. most fall at your feet. some fly a few feet. very few make it many feet.
then imagine your chances of making a full-court basket (94 feet, 9.4" diameter ball in 18" hoop) and then divide those odds by the several orders of magnitude smaller that viruses are relative to us.
wearing masks (or gloves) outside makes no sense. you might as well walk around with your own lightning rod too then.
that site serves to reduce anxiety rather than transmission risk. none of the graphs and pull quotes, presumably the strongest arguments they could find, address the added risk reduction of masks above other prevention measures like distancing, and especially not concerning outdoor, non-group settings for the general public.
emergency personnel, medical professionals, and essential business workers should wear masks because they are at elevated, face-to-face risk.
> 99% of the reduction in transmission comes from physical distancing alone while inside of closed spaces with strangers.
This is an extremely strong statement. Although it might be plausibly true, my impression is that the transmission of the disease isn't well enough understood to make such assertions with confidence.
Can you cite a reference for your claim?
I think it is agreed that physical distancing alone while inside of closed spaces with strangers is an extremely good idea. Wearing masks is, potentially, also an extremely good idea.
Shouldn't we adopt any and all measures that have the potential (not certainty; potential is enough) to substantially cut down on Covid-19 transmission, and whose economic and other costs are comparatively modest? Even if we later determine that only one of these measures was really necessary, I doubt that we'll regret our efforts.
"For example, look at the numbers in South Korea, Japan, etc. (where mask-wearing is common) compared to ours."
There seems to be a huge difference in the trajectory of cases in Japan, vs South Korea, so I don't know what you think you're saying, if you group them together. In South Korea, cases went up and then apparently flattened out almost completely. In Japan, the graph I saw has been lower than in other places but is, almost uniquely, not flattening so far, even in the way that Italy or the US has.
So it makes no sense to me to combine them and say "look, that is the example". If one is the example, the other most likely isn't.
I wear masks in public, even though I have no comorbidities, because of all the people I might subsequently spread it to if I got it. Remember that asymptomatic transmission for several days is common.
Putting on a mask takes a few seconds, so compared to all the suffering it might prevent, even at 0.01% probability, it's well worth it.
no one is arguing that you disregard others, especially those who have comorbidities, only that a mask adds negligible risk reduction outside, above and beyond the natural physical distancing of strolling down the sidewalk.
Do you have evidence that risk reduction outside is very small? I haven't seen any, and I think it would be nearly impossible to collect such evidence.
A plausible rule of thumb seems to be: if you could smell someone's cigarette smoke, you could inhale their viruses. I certainly smell smoke from smokers I pass on the street.
there are no studies done, because, as you note, it would be difficult and costly, and it's a simpler (and more easily followable) message to tell people to wear masks all the time.
but here's some additional intuition:
1. it's true that virus particles are roughly the same size as smoke particles, but infected people exhale virus "pucks" that are agglomerations of multiple viruses and water, leading them to fall while smoke floats (giving us the 3-6 foot rule, per prior coronavirus studies).
2. a single virus particle in the air without water could float around but is overwhelmingly likely to fall apart quickly. the air doesn't provide the countervailing forces to keep it together, and the bombardment of energies from all around also pull it apart.
3. the fact that a homemade mask allows smoke right through but filters out some portion of the virus pucks (as per your prior link) is evidence in itself of the differential affinities of smoke and virus pucks.
but let's face it, most people wearing masks (outside) do it because they think it's protecting them from the filthy other people. however, if you're sick, all you're doing is concentrating the virus pucks in one place right in front of a face we'll each touch 30 times an hour. no lay person consistently observes the contamination rules that hospital personnel do, especially when infection rates are <0.1% and failure to do so has no obvious downsides. masks could in fact be more dangerous because of a false sense of security.
