Here. I guess I'm persuaded it's clearly a factor (much more than fomites), but it's not that easy, as the author explains via helpful analogy:
[I]t is useful to use cigarette or vaping smoke (which is also an aerosol) as an analog. Imagine sharing a home with a smoker: if you stood close to the smoker while talking, you would inhale a great deal of smoke. Replace the smoke with virus-containing aerosols, which behave very similarly, and the impact is similar: the closer you are to someone releasing virus-carrying aerosols, the more likely you are to breathe in larger amounts of virus....
If you are standing on the other side of the room, you would inhale significantly less smoke. But in a poorly ventilated room, the smoke will accumulate, and people in the room may end up inhaling a lot of smoke over time. Talking, and especially singing and shouting increase aerosol exhalation by factors of 10 and 50, respectively. Indeed, we are finding that outbreaks often occur when people gather in crowded, insufficiently ventilated indoor spaces, such as singing at karaoke parties, cheering at clubs, having conversations in bars, and exercising in gyms....
[D]roplets move ballistically—they fly like a cannonball from someone’s mouth and then travel through the air until they either hit something (worst case someone else’s eyes, mouth or nostrils) or fall to the ground. Aerosols on the other hand, act like smoke: after being expelled, they don’t fall to the ground, but rather disperse throughout the air, getting diluted by air currents, and being inhaled by others present in the same space. Contact tracing shows that, when it comes to COVID-19, being outdoors is 20 times safer than being indoors, which argues that aerosol transmission is much more important than droplets; outdoors, there’s plenty of air in which aerosols can become diluted; not so indoors....
The visual analogy of smoke can help guide our risk assessment and risk reduction strategies. One just has to imagine that others they encounter are all smoking, and the goal is to breathe as little smoke as possible. But COVID-19 is not very contagious under most situations, unlike, for example, measles: the CDC says that 15 minutes of close proximity to a COVID-19 infected person often leads to contagion, which provides an estimate of how much “exhaled smoke” one may need to inhale for infection. Inhaling a little whiff of “smoke” here and there is OK, but a lot of “smoke” for a sustained period of time and without a mask is risky....
