Covid and air pollution, between good weather and toxic relationship

The Covid-19 pandemic has certainly cleared up the polluted skies of large confined metropolises, but experts are especially worried about a possibly toxic relationship between air pollution and the respiratory virus.

With the proliferation of containment measures around the world, with traffic restrictions and the economic crisis, multiple studies have shown a sometimes spectacular drop in the concentration of certain air pollutants in the United States and China. or in Europe.

The impact was particularly visible for nitrogen dioxide (NO2) and particulates. For example, during spring lockdowns, Spain saw a 61% drop in NO2 in the air, France 52% or Italy 48%, according to the European Environment Agency.

While air pollution is believed to be responsible for 7 million premature deaths worldwide each year, these falls, even temporary ones, have certainly saved lives, according to some experts.

“In the short term (mainly the acute effects linked to extremely high pollution), we estimate that 2,190 and 24,200 deaths linked to air pollution were avoided respectively in Europe and China during the spring confinements”, Paola Crippa, air quality expert at Notre-Dame University in Indiana, told AFP.

“If we take into account the long-term effect (chronic respiratory problems, cardiovascular disease, lung cancer, etc.), the number of deaths avoided is much higher”, she assures: between 13,600 and 29 500 for Europe, and between 76,400 and 287,000 in China, according to various scenarios.

Same targets

“Unless there is a huge rebound in pollution, which I don’t believe, the long-term exposure of people in Europe will have been reduced thanks to the drop in fossil fuel consumption in 2020,” and this will have an effect on the health risk in the long term, ”adds Lauri Myllyvirta, from the Center for Research on Energy and Clean Air (CREA), which estimates the deaths avoided thanks to the spring containment at 11,000 in Europe .

While these potential lives saved are at least one positive side of a pandemic that has so far killed 1.3 million people, this experience is above all, for defenders of healthy air, further proof of the need to fight against this harmful pollution.

Especially since studies are accumulating to highlight a probable unfavorable impact of air pollution on Covid-19, its severity, and even its mortality.

“The results have been repeated in such different contexts and countries that I think the combined evidence is starting to be strong,” says Lauri Myllyvirta.

According to a study published at the end of October in Cardiovascular Research, long-term prior exposure to fine particles PM2.5 increased mortality linked to Covid-19 by 15% globally, with disparities by region (27% in Asia Eastern, 19% in Europe, 17% in North America).

This virus and PM2.5, already accused of contributing to cardiovascular and pulmonary diseases, attack the same targets.

“They are responsible for the same thing: inflammation of the vascular system of the lungs, secondary pneumonia, hypertension, and also myocardial infarction and heart failure”, explains to AFP Dr. Thomas Münzel, cardiologist at the University of Medicine of Mainz , who participated in the study.

“Double strike”

So in the event of pre-existing cardiovascular disease, “you are particularly at risk when you are infected with Covid”, he adds.

Analyzes of more than 3,000 counties in the United States found that an increase in the average fine particle concentration of 1 microgram / m3 corresponded to an 11% increase in mortality from the coronavirus.

In their study published in early November in Science Advances, the authors warn, however, against overinterpreting these statistics, emphasizing the need for further work.

As to the impact of exposure to air pollution during illness, it is not known.

“I am sure that the short-term reduction in air pollution is having an impact, although we do not have data at this time,” comments Dr Münzel.

Clues are also beginning to emerge on the mechanism of interaction, in particular the role of the ACE-2 receptor which facilitates the entry of the SARS-CoV-2 coronavirus into cells.

A role described in the Spring in the Journal of Infection as “the double strike hypothesis”: the fine particles would contribute to damage this receptor which would allow more virus to enter the infected patient, a situation potentially aggravated by chronic exposure to NO2 which weakens the lungs.

A situation which would be particularly worrying in certain polluted countries which are undergoing a new assault from the virus, such as India.

With the arrival of winter, “season of pollution”, “it is obviously a great cause for concern for Covid patients”, warns Lauri Myllyvirta.

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