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The Covid-19 pandemic has certainly cleaned up the polluted skies of large confined metropolises, but experts are particularly concerned about a possible toxic relationship between air pollution and the respiratory virus.
With the proliferation of containment measures around the world, with traffic restrictions and 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 particulate matter. For example, during the spring blockages, Spain experienced a 61% drop in NO2 in the air, France by 52% or Italy by 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 borders”, thus indicates to AFP Paola Crippa, air quality expert at Notre Dame University in Indiana.
“If we take into account the long-term effect (chronic respiratory problems, cardiovascular diseases, lung cancer …), the number of deaths avoided is much higher”, he assures: between 13,600 and 29,500 for Europe, and between 76,400 and 287,000 in China, according to different scenarios.
– Same goals –
“Unless there is a huge rebound in pollution, which I do not think, the long-term exposure of people in Europe will be reduced thanks to the decline in fossil fuel consumption in 2020, and this will have an effect on the risk for long-term health “, adds Lauri Myllyvirta, of the Center for Research on Energy and Clean Air (CREA), who estimates that 11,000 deaths in Europe have been avoided thanks to spring containment.
While these potential saved lives are at least one bright 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 this harmful pollution.
Especially as studies are piling up to highlight a likely adverse 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 in late October in Cardiovascular Research, previous long-term exposure to fine particles PM2.5 increased Covid-19 mortality by 15% globally, with disparity 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 disease, attack the same targets.
“They are responsible for the same thing: inflammation of the vascular system of the lungs, secondary pneumonia, hypertension, and even myocardial infarction and heart failure,” explains Dr. Thomas Münzel, cardiologist at the Medical University of Mainz, who participated in the study.
– “Double shot” –
So, in the case of pre-existing cardiovascular disease, “you are in particular danger when you are infected with Covid,” he adds.
Analyzes of more than 3,000 US counties have shown that an increase in the average concentration of fine particles of 1 microgram / m3 corresponds to an 11% increase in coronavirus-related mortality.
In their study published in early November in Science Advances, however, the authors caution against over-interpretation of these statistics, stressing 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 currently have no data,” comments Dr. Münzel.
Clues to the mechanism of interaction are also beginning to emerge, particularly 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 of the Journal of Infection as “the double hit hypothesis”: fine particles would contribute to damage this receptor which would allow more viruses to enter the infected patient, a situation potentially aggravated by chronic exposure to NO2 which weakens the lungs.
A situation that would be particularly worrying in some polluted countries that are experiencing a new onslaught of the virus, such as India.
With the onset of winter, “pollution season”, “it is obviously a great cause for concern for Covid patients”, warns Lauri Myllyvirta.
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