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Aerosols Are The Answer (and the problem)
What happens when we cough, sneeze, talk, and sing
July 2, 2020

M
ac Ernest is a retired physician. Before moving to Oriental in 2014,
mac ernest
Mac Ernest
Mac was the Chair of the Dept of Obstetrics and Gynecology at Carolinas Healthcare in Charlotte. Prior to that he was Professor of Obstetrics-Gynecology at Wake Forest medical school in Winston-Salem.

In addition to patient care and teaching, his research has included studying infectious diseases.

Mac has agreed to provide a series of columns about COVID-19. This column was prepared with the assistance of Sharon Stephenson MD, Ros Cheetham MSc and Diana Silimperi MD.


Ever been in a park and without seeing them knew that someone was smoking a cigar?

Or been on a walk and knew that someone was burning leaves in their yard?

You recognize these smells because of aerosols, which are tiny solid or liquid particles that are too small to see and that can float in the air for minutes or hours before settling onto a surface or the floor. Burning tobacco or leaves produces aerosols that cause the smells that let you know about their presence.

Aerosols are also produced when we cough, sneeze, talk, and sing.

When we do those things, aerosols from deep in our lungs go out of our mouth or nose and into the surrounding air. If we are not sick, they are usually of no concern. We cannot see them and don’t even know they are there. If we are sick (or even if we don’t feel sick but have a virus or bacteria in our lungs), they can be very important to those around us because the aerosols that we produce can carry bacteria or viruses which can remain in the surrounding air for extended periods. Just as we inhale smoke from a nearby fire that we cannot see, we inhale the aerosols in the air that others produce when we are in a room, a car, or other contained space where others are or have recently been.

We know that the spread of COVID-19 can be from surface contact (touching a contaminated surface and not washing our hands well before touching our face or food) and can also be from inhalation of the virus from the air. We are familiar with respiratory droplets (visible particles that are ejected when someone coughs or sneezes), but we don’t always think about these invisible aerosols which may be a greater source of infection than even the respiratory droplets. Because aerosols are produced deeper in our lungs than the larger respiratory droplets, aerosols have the potential of spreading more coronavirus particles that those droplets from our nose or mouth.

Studies are now demonstrating that many COVID-19 infections are the results of coronavirus-carrying aerosols produced by infected individuals (symptomatic or not) that are inhaled by healthy people in their vicinity, who then become sick because of inhaling enough of the virus.

Since we cannot see or detect these aerosols in the surrounding air and do not know when we are breathing them, what can we do to reduce our risk of becoming infected because of them? (keeping in mind that the BEST way to reduce our risk is to stay at home as much as possible and avoid potentially infected persons in the first place!):

  • Minimal effectiveness: Avoid or minimize time in rooms, stores, or cars with poor ventilation where others are or have been talking, coughing, or sneezing, especially if they were not wearing masks. Even if others are gone, aerosols that may contain virus particles can linger in the air and you can breathe them for some time after other people have left.
  • Moderate effectiveness: Eat or shop outdoors as much as possible where fresh air and breezes dilute aerosols and reduce the amount you may inhale.
  • Significant effectiveness: Spend your time outdoors and around people who are socially distancing and wearing masks or facial coverings! Masks and face coverings worn by others prevent most of their respiratory droplets AND aerosols from getting into the air in the first place which then reduces the amount that you may breathe. In turn, when you wear a mask, you are not only reducing their respiratory droplets that are in the air from entering your nose and mouth, but you are also preventing others from breathing your droplets and aerosols and returning the favor. Your mask helps you some, and others a LOT!

The idea of aerosols that we cannot see or smell that can make us sick can be overwhelming and even a bit frightening. Understanding the concept, however, can lead to a wonderfully simple way to combat this hidden menace: MASKS! Be a good example and wear a mask or face covering when in public, and tell your friends about aerosols and why it’s so important to reduce them.

And by the way, if you read or hear that masks are dangerous or unhealthy to the wearer, that has NOT been my personal experience. I have worn a surgical mask over 4000 times in my career (sometimes for hours at a time) and have many colleagues that have worn them for at least that many times. With all of that cumulative experience, I have NEVER heard of a single problem with a face mask.

If we can convince enough folks to wear masks or face coverings when out and about and around others, we can reduce the threat that aerosols represent, and have a quicker and safer exit from this pandemic.

References:
Video of aerosols from cough
Effectiveness of surgical face masks
Effectiveness of cloth masks against aerosol spreading