Under an aerosol regime, we would have different rules for the indoors and the outdoors (especially since, in addition to the diluting power of air, sunlight quickly deactivates viruses.) We would mandate masks indoors regardless of distancing, but not necessarily outdoors. Marr told me that she wears her mask outdoors only if she’s interacting with people, if she’s in a crowd, or if she cannot maintain distance. Yet, in the United States, many locales are mandating masks indoors and outdoors under the same rules, forcing even the solitary person walking her dog to mask up. And there are places, such as Chicago, where beaches are closed because officials fear crowds, but indoor restaurants and gyms remain open with mild restrictions.
As another example, you may have seen the many televised indoor events where the audience members are sitting politely distanced and masked, listening to the speaker, who is the only unmasked person in the room. Jimenez, the aerosol expert, pointed out to me that this is completely backwards, because the person who needs to be masked the most is the speaker, not the listeners. If a single mask were available in the room, we’d put it on the speaker. This is especially important because cloth masks, while excellent at blocking droplets (especially before they evaporate and become smaller, thus more likely to be able to float), aren’t as effective at keeping tinier aerosol particles out of the wearer’s mouth and nose once they are floating around the room (though they do seem to help). We want to see the speaker’s mouth, one might say, but that is a problem we can approach creatively—face shields that wrap around the head and seal around the neck, masks with transparent portions that can still filter, etc.—once we stop ignoring the problem. In fact, designing a high-filtration but transparent mask or face shield might be an important solution in classrooms as well, to help keep teachers safe.
Once we pay attention to airflow, many other risks look different. Dylan Morris, a doctoral candidate at Princeton and a co-author of the first paper to confirm that the virus could remain infectious in aerosolized form, under experimental conditions, showed me a clip of a group of people in a conga line, separated six feet apart by ropes. They were merrily dancing, everyone standing behind someone else, in their slipstream—exactly where you don’t want to be, inhaling aerosol clouds from panting people.