A Blog by Jonathan Low


Apr 19, 2021

Do People Still Need To Wear Masks Out of Doors?

Probably still a good idea, especially in crowded spaces and when close to others. It also sends a message to the reckless or ideological that the pandemic is not yet over. 

But data increasingly suggest that as the percentage of the vaccinated populace grows, going maskless is now within the realm of planning. JL

Shannon Palus reports in Slate, image by Clay LeConey in Unsplash:

When it comes to coronavirus spread, evidence shows that being outdoors is safe. While it’s important to mask in outdoor crowds or if hanging out close to someone, when walking unmasked and briefly pass someone, you or the person you’re passing would have to have an asymptomatic infection, and then (both) would have to be exhaling and inhaling at the right moment, exchanging enough particles to seed infection: “A probability of being struck by lightning.” A threshold at which outdoor mask mandates are lifted could be 10 hospitalizations per 100,000 people, with 40% having received their first vaccine dose. With that in mind, “many states could do this now!”

One of the last times I stepped outside my Brooklyn apartment without a mask on was in early spring 2020, just before the state issued a mask mandate. I remember because as my dog peed on a tree, a neighbor asked me pointedly where my mask was. Where I live, almost everyone wears a mask when they go outside. If a person sipping from an iced coffee with their mask pulled down approaches someone else on the sidewalk coming the other way, they will usually yank the mask back up, as if they’ve been caught partially dressed. The other day I noticed a woman sitting on a hill in the middle of a field with her face covered. There was no one near her.

For a while now, this has felt a little unnecessary, if understandable, given that we were still learning things about the virus and were trying to be as careful as possible. But now, as we’ve come to know more about the virus, as vaccinations are ramping up, and as we’re trying to figure out how to live with some level of COVID in a sustainable way, masking up outside when you’re at most briefly crossing paths with people is starting to feel barely understandable. Look: I believe masks (and even shaming) are indispensable in controlling the spread of the coronavirus. Despite early waffling, public health experts are virtually unanimously in support of them and have remained so even as our early dedication to scrubbing surfaces and Cloroxing veggies wound down.

In other words, as the pandemic has progressed, so has our understanding of what safety measures are truly most useful, and which aren’t worth the alcohol wipes. And I would like to calmly suggest that now is the time we should consider no longer wearing masks when we walk around outside.

I am not suggesting this simply because I am very sick of wearing a mask at all times outside my home. When it comes to coronavirus spread, evidence shows that being outdoors is very, very safe. A paper published in Indoor Air looked at 1,245 cases in China and found just one instance of outdoor transmission, which involved people having a conversation, which means they had to be close to one another for some period of time and face to face. According to data from the Health Protection Surveillance Centre, shared earlier this month with the Irish Times, of 232,164 cases in Ireland, just 262 were associated with “locations which are primarily associated with outdoor activities.” That is, about 0.1 percent. A meta-analysis published online in November in the Journal of Infectious Diseases suggests it’s possible the upper bound of cases potentially contracted outdoors is higher; it estimates that the total is less than 10 percent. When I called Nooshin Razani, an author on that report and an associate professor of  epidemiology and biostatistics at the University of California, San Francisco, she emphasized that the real number of instances of outdoor transmission was “probably lower” than 10 percent, since the cases she and her team counted were sometimes murky: cases that occurred at construction sites, or summer camps where people were sharing bunks. That is, these scenarios likely involved some indoor time as well. They also tended to involve people who were spending time together over a period of days. “Most of the cases that happened outdoors had something about the circumstances you could point to and say, ‘That was a risk,’ ” says Razani. Just one case involved joggers—who were jogging together. Still, Razani said she couldn’t comment on whether it was OK to go maskless on a sidewalk where you’re able to mostly, but not perfectly, stay distanced from others. In an article in National Geographic by science writer Tara Haelle, other experts note that yes, we have data that the outdoors is very safe, and yet, if you can’t distance, even briefly, you might want to pull up your mask, partly out of respect, and also just to be safe.

I have to say: I don’t agree! It’s true that nothing is 100 percent safe. But because little particles floating through the air are a main concern with COVID, the outdoors is very, very safe. Anything you exhale will just be diluted very quickly, especially if you’re moving around. Yes, the coronavirus can spread in other ways. As Razani said, “If you’re right next to someone and you spit on them outdoors, it’s not going to magically protect you from their spit.” But that comment illustrates that the risk of getting COVID while briefly coming within 6 feet of someone outside is so small that your exchange of fluids would almost have to be purposeful. Zain Chagla, an infectious diseases physician with McMaster University, recently wrote an op-ed in the Toronto Star noting that last summer’s outdoor gatherings coincided with an all-time low of cases in the city. While it’s important to mask in outdoor crowds or if you’re hanging out close to someone in a park, Chagla explains, the main message should be that the outdoors is a safe place to be. He gave me a rough sense of how unlikely outdoor transmission is in the scenario where you’re walking unmasked on the sidewalk and briefly pass someone. First, you or the person you’re passing would have to happen to have an asymptomatic infection, he explained, and then everyone would have to be exhaling and inhaling at just the right moment, and also, exchanging enough particles to actually seed another infection: “You’re talking about a probability of getting hit by a car, and being struck by lightning.”

So why is it still officially considered best practice to do what Monica Gandhi, an infectious disease doctor at UCSF, says “almost becomes ridiculous” as vaccinations increase? Whether we wear masks at all times outside has become a combination of politics and regional attitudes toward the virus—not science. Early on in the pandemic, wearing a mask became a symbol that you took the virus seriously and were willing to listen to public health officials; not wearing one was a symbol that you valued personal freedoms and, weirdly, the president of the United States. And maybe in the beginning of the pandemic, it made sense to mask up as much as possible—we were in an emergency, and it felt sort of appropriate to signal to one another that we all understood the seriousness of this virus. But masks shouldn’t go on being a blunt-force declaration of safety; we should embrace their nuanced use, starting with the idea that they might be overkill in some settings outdoors. This is especially true for people who have been fully vaccinated, and for whom wearing a mask in an already very-low risk setting is more of a show of participation in pandemic society than a medical necessity. “What I’m saying is really heterodoxy in San Francisco,” says Gandhi, who has authored multiple papers on just how important masks are. “Here, if you don’t wear a mask, everyone glares at you.” But she noted that on a recent trip to Austin, Texas, she saw lots of masks inside but not really outdoors. Such a world was possible. “I was so fascinated—I was like, you know what, this is consistent with biology.”

Gandhi thinks that there should be a clear threshold at which cities that have outdoor mask mandates lift them entirely. That threshold could be 10 hospitalizations per 100,000 people, she suggests, with 40 percent of people having received their first vaccine dose. (She based this in part on a piece she co-wrote for the Washington Post.) With that potential standard in mind, Gandhi wrote in a follow-up email, “many states could do this now!” To be clear, the choice of when to do this should not be based on one person’s quick calculation; her point and mine is that public health officials would do well to figure out a science-based way to ease the mask restrictions where it makes sense, without lifting them entirely. And those cautious souls living in places with no mandates at all should consider joining their neighbors going for walks without masks. Gandhi also thinks that adjusting the recommendation would help engender more trust in public health officials, by letting people know they aren’t being asked to take precautions arbitrarily. She says she has written the San Francisco Department of Public Health in her capacity as a mask researcher asking for more nuanced guidance for outdoor masking but has not heard back. While I’m not superinterested in breaking my city’s social norms—especially while our cases are still high—our collective agreement to mask up obsessively outdoors comes at a cost. Masking can be exhausting. It makes recreation really annoying, especially as the weather warms. It makes it difficult to escape, even temporarily, from the pandemic. It deprives us of seeing one another’s smiles! I’m aware that these are also arguments deployed by those who decry all masking, even indoors. But the point is that masking shouldn’t be about signaling what side you’re on—it should be about using a tool in response to risk. Being overly vigilant about masks when they are not important makes it more difficult to keep wearing them when they are. Also, I fear that it is making us look a little ridiculous.


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