The confinement mitigated air pollution in large metropolises, but at the same time experts warn of a possibly toxic relationship between this phenomenon that is harmful to health and the respiratory virus SARS-CoV-2.
After the multiplication of restrictive measures in the world, which affected from industrial activity to road traffic, several studies showed a sometimes spectacular drop in the concentration of some pollutants in the air, both in the United States, China and Europe .
The impact was especially noticeable in terms of nitrogen dioxide (NO2) and fine particles. For example, in the first confinement, Spain recorded a 61% drop in NO2 in the air, France, 52%, and Italy, 48%, according to the European Environment Agency.
While air pollution is estimated to be responsible for 7 million premature deaths each year, these drastic reductions, even temporary, saved lives, according to some experts.
“In the short term, we estimate that 2,190 and 24,200 deaths will have been prevented in Europe and China respectively during the spring lockdown,” Paola Crippa, an air quality expert at Notre Dame University in Indiana, told AFP.
In the long term, the number of deaths derived from chronic respiratory problems, cardiovascular diseases, lung cancer, etc. that will be avoided “will be higher”: between 13,600 and 29,500 in Europe, and between 76,400 and 287,000 in China, according to various scenarios of economic recovery, adds Crippa.
The same white
“Unless there is a big spike in pollution, which I don’t think, the long-term exposure of the population in Europe will have been reduced thanks to the drop in fossil fuel consumption in 2020 and this will have an effect on health risk long-term, “explains Lauri Myllyvirta, from the Center for Research on Energy and Clean Air, who estimates the deaths averted in the first lockdown at 11,000 in Europe.
While this is good news in the context of a pandemic that has so far killed 1.3 million people in the world, this experience is above all for some further proof of the need to fight against this harmful pollution.
All the more so since studies are accumulating that indicate that this phenomenon could worsen the severity and even mortality of covid-19.
“The results have been replicated in such different contexts and countries that the combined evidence is starting to be strong,” according to Lauri Myllyvirta.
According to a study published in October in the journal Cardiovascular Research, previous long-term exposure to fine PM2.5 particles increased mortality related to covid-19 by 15% globally, with disparities between regions (27% in Asia Eastern, 19% in Europe, 17% in North America).
This virus and PM2.5, related to cardiovascular and pulmonary diseases, attack the same targets.
“They are responsible for the same: inflammation of the vascular system of the lungs, secondary pneumonia, hypertension and also myocardial infarctions and heart failure,” explains Dr. Thomas Münzel, a cardiologist at the Mainz Medical University (Germany), to AFP. who participated in the study.
Therefore, in case of contagion with Covid-19, the risk is greater if you already suffer from a pre-existing cardiovascular disease, it adds.
Several analyzes of more than 3,000 counties in the United States found that a rise in the average concentration of fine particles of 1 microgram / m3 corresponded to an 11% increase in mortality related to the coronavirus.
In their study published in early November in Science Advances, the authors nonetheless warned against an overinterpretation of these statistics, underscoring the need for further work.
On the other hand, knowledge is beginning to emerge about the interaction mechanism, especially the role of the ACE-2 receptor that facilitates the entry of the SARS-CoV-2 coronavirus into cells.
A role described in the Journal of Infection as the “double whammy hypothesis”: fine particles would contribute to damaging this receptor, which would allow more virus to enter an infected patient, a situation potentially aggravated by chronic exposure to NO2 that weakens the lungs .
And with the arrival of winter, “pollution season”, “it is obviously a great cause of concern for patients with covid-19”, warns Myllyvirta.
It is also so in countries with high levels of contamination that suffer a new onslaught of the virus, such as India.