Coronavirus: specialists explain why you have to wear a chin strap and keep your distance outside – Telam

Nearby aerosol contagion is one that occurs within two meters of the infected person.

Although open spaces greatly reduce the risk of inhaling aerosols (small particles that humans emit upon exhalation) that accumulate in closed environments, nearby (less than two meters) there may be a risk of contagion, which is why specialists have said that you must continue to wear a chin strap and keep a good distance even outdoors.

“Two types of contagion must be distinguished: near and far. When we breathe out, we emit aerosols or small particles of respiratory fluid that may contain infectious viruses. Nearby aerosol contagion is that which occurs within two meters of the infected person, where the concentration of exhaled aerosols is higher and therefore, the risk of exposure is high “, Andrea Pineda Rojas, researcher at the Center for research on the sea and the atmosphere (CIMA) and Conicet.

And he continued: “In closed and poorly ventilated environments these aerosols build up in the air and although we are more than two meters apart, when we breathe we can end up inhaling. enough to be infected, that’s what we call contagion. distance “.

The specialist explained that “superpropagation events, such as the case of the American choir (Skagit) where people who were up to 13 meters from the person were infected with Covid-19, show that remote contagion does not is not only likely but quite common when the factors that favor these events combine “.

In this sense, “promoting meetings and outdoor activities is very important because abroad the probability of contagion is much lower, even if it is not zero.

“Now,” he says, “when you talk to another person at a distance of less than two meters, you are exposed to visible drops of saliva and also to a higher concentration of potentially infectious aerosols; the quantity of aerosols emitted depends on the respiratory activity (if he speaks loudly, sings, laughs, he is taller) and its infectious power depends on the stage of the disease in which the person is, ”he said. he describes.

So, whether outside or inside, “being less than two meters away, the risk of contagion is high; in closed environments it is very high, but outdoors we have no assurance that it is not, unless there is enough wind for the aerosols to dilute quickly. “

Regarding remote contagion, air quality expert and professor at the National University of Colombia Néstor Rojas added an example to understand how aerosols work.

“If someone is in a park and smells of cigarettes, look around and see that the person smoking is more than two meters away, it means that the atmospheric conditions were not sufficient to dilute the smoke they feels “, He described.

“If this happens with cigarette smoke – he continued – it can be the same with aerosols emitted by a person who contains the virus; and this analogy helps us to underline that even outdoors, the ventilation is sometimes poor, that is to say that the atmospheric dispersion, and therefore the dilution of aerosols in the air, is not sufficient ”.

“The promotion of meetings and outdoor activities is very important because abroad the probability of contagion is much lower, even if it is not zero”“

Andrea Pineda Rojas

In this sense, Pineda Rojas explained that “Ventilation, which is the renewal of the air, is a concept also used to study outdoor air pollution: the atmosphere is said to be well ventilated when there is enough wind to mix the air. polluted with clean air “.

The risk of contagion “nearby indoors or outdoors is similar, except in windy conditions”.

“There are very few studies on the transmission of Covid-19 outdoors and it must be taken into account that monitoring infections in open spaces is probably much more difficult than in closed environments,” he said. -he declares.

“But we know,” he continued, “that in certain activities such as demonstrations, groups of people doing gymnastics, crowded bars, that is, where there are a lot of people. people without a mask, talking very loudly or doing physical activity, the aerosol emission is potentially high and there is no guarantee that the atmospheric dilution will be sufficient. Even so, the possibility of accumulation is considerably lower than in closed environments. “

“Among the evidence is contagion outside nearby, usually associated with people speaking without distance or masks. So when we say that outside the risk of contagion is much lower than in closed environments, we have to keep in mind that it is on average, and the risk of contagion near the interior or the exterior is similar, unless it’s windy, ”he said.

Chinstrap

Regarding chinstrap, researcher Conicet underlined that “What is recommended is that homemade masks have at least three layers and fit well over the entire face. Fit is very important.. There are a lot of people who use it in bulk and it doesn’t work for aerosols, both to reduce their emissions and their inhalation, ”he said.

They recommend that homemade masks have at least three layers and fit well over the entire face.

In this regard, Néstor Rojas clarified that “we can have a very good filter material but badly used, the efficiency of the chin strap decreases by 50% or more due to the lack of adjustment”, he also described that “it There is a type of chin strap that has a valve on the sides and in these we have seen that they allow the release of aerosols so they should not be used “.

Finally, Pineda Rojas argued that “What is being promoted today is the use of several layers of protection because it is the sum of the measures that can considerably reduce the risk of contagion: that the meetings take place outdoors, with distance and chinstrap; that if it is to be indoors, the environment is well ventilated with as few people as possible and for the shortest time possible, in addition to distance and chinstrap; in any case the risk is zero if you do not stay at home.