Air pollution and Covid-19: an explosive mixture for health?

The most polluted regions in Europe are also those where Covid-19 kills the most. In all, 78% of deaths from coronavirus in Europe are concentrated in the five most polluted regions, found Yaron Ogen, researcher at the Institute of Earth Sciences at Martin Luther University in Halle, in a study preliminary published in the journal Science of Total Environment, announced the German university Monday April 20.

This analysis attempts to establish a link between exposure to nitrogen dioxide, a pollutant generated mainly by the exhaust pipes of diesel cars, and the lethality of the virus in France, Italy, Germany and Spain. The observation seems clear: the two areas where the concentration of nitrogen dioxide is the highest - the Po plain in northern Italy, and around Madrid, the Spanish capital - also happen to be the ones with the highest victims of Covid-19.

Better identify those at risk?

These regions have particularly toxic environments due to the presence of large cities with a lot of traffic, like Milan, Turin and Madrid, surrounded by mountain ranges which prevent pollution from dispersing.

"I chose nitrogen dioxide because its harmful effects on health are well documented and the statistical data are easy to find", explains Yaron Ogen, contacted by France 24. Prolonged exposure to this pollutant can cause similar lesions those considered to be co-morbidities of the coronavirus, such as lung damage, breathing problems or heart failure.

The pollution may have "weakened the respiratory system which is thus less well equipped to fight against the virus", notes the researcher based in Germany. For him, this could notably explain why people with no apparent comorbidity find themselves struggling to survive in the face of the coronavirus. "Perhaps these environmental factors should also be taken into account to determine who are the people most at risk", judge Yaron Ogen. Long exposure to air pollution "has

Environmental alarm bell

He is not the only one to sound this environmental alarm. Already at the time of the Sars epidemic, between 2002 and 2004, Chinese researchers had pointed out that the most polluted cities also had the highest number of deaths due to this "big brother" of Covid-19. 

A British study, posted online in prepublication and similar to that conducted by the researcher based in Germany, comes to the same conclusion. In the UK, Covid-19 has claimed more lives in areas with the highest particulate matter pollution, scientists at Cambridge University have found, reports the British daily The Guardian.

Ditto in the United States, where "a very small increase in the level of concentration of fine particles in an area is associated with a 15% increase in the fatality rate of the coronavirus," observed researchers from the school of health of the Harvard University in Boston, in a study published April 7. 

Pollution is not the only possible explanatory factor

But all these researchers also emphasize that we must be careful not to draw hasty conclusions from these first observations. "The correlation found does not necessarily mean a causal link", explains Yaron Ogen. Other factors could just as easily explain that these highly polluted regions account for the greatest number of deaths due to Covid-19.

Pollution levels are therefore generally higher in the most populated regions and "the population density favors the spread of the virus since it makes social distancing more difficult", notes Rosie Cornish, researcher at Bristol Medical School.

In addition, northern Italy and Madrid are among the first regions in Europe where the Covid-19 epidemic has broken out. It is therefore not surprising that the number of victims is higher since the virus has been rife there for longer. A regional level analysis of pollution may not be the most relevant to make this kind of comparison: "We generally prefer a more local level of observation because exposure to air pollution can vary a lot from one address to another in the same city, depending on whether you live near a major road or on the edge of the countryside, "underlines Anna Hansell, professor of environmental epidemiology at the University of Leicester, the UK.

"In order to be able to establish a true causal link, more than twenty serious studies are needed on this subject," said Mark Goldberg, epidemiologist at McGill University in Montreal, interviewed by the Guardian. Yaron Ogen does not say anything else: "All I hope is that this work inspires other researchers to look even closer." 

For him, finding an answer to this question of causation could prove critical for the prevention of future epidemics. Indeed, at a minimum, this should prompt the authorities to put in place special protection measures for the populations living in the most polluted areas. But to limit the health risk, Yaron Ogen judges that "if the lethality of the virus is influenced by the level of pollution, it is perhaps the whole model of economic development that must be reinvented in order to make it less dependent on polluting activities ". Coronaviruses would thus be added to the growing list of reasons for applying resolutely greener development policies. 

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