A team of researchers from Aarhus University in Denmark and the University of Siena in Italy has explored the possible link between air pollution and COVID-19.
The study, published in Environmental Pollution, found a clear correlation between air pollution and death rates from COVID-19 in Italy. It also offers some reasons as to why this might be the case.
The rapid spread of the SARS-CoV-2 virus has meant that there has been little time for scientists to determine what affects its speed of transmission and how lethal it can be.
Scientists have, however, already identified some factors that might affect the lethality of COVID-19. These factors include underlying health conditions, a person’s age, and their sex.
They have based this information on data inferred from previous viral respiratory illnesses or from countries, such as Italy or China, that had early exposure to the virus.
The authors of the paper in Environmental Pollution discovered a possible correlation that scientists had not previously addressed — a link between air pollution and the number of deaths from COVID-19.
This correlation became apparent when they looked at the situation in Italy.
Official figures from the Italian government show a significant variation in the lethality of the virus, depending on geographic areas.
According to these figures, northern regions of Italy, such as Lombardy or Emilia Romagna, saw a lethality rate of 12%. In the rest of the country, the lethality rate was around 4.5%.
The authors note that there may be a range of explanations for these variations. The differences may be due to the way each region records deaths and infections or the fact that these two regions had relatively older populations.
The researchers suggest that air pollution is another possible factor that could explain this variation.
As well as having a significantly higher death rate from COVID-19, Lombardy and Emilia Romagna also have some of the worst air pollution levels, not just in Italy, but across all of Europe.
The researchers drew on data from the NASA Aura satellite and the European Environment Agency’s Air Quality Index.
The two datasets enable a clear and accurate picture of the relative air pollution in different geographic regions across Europe.
As well as being major centers for industrial production, which are a key cause of air pollution, the authors note that the geographic and climatic conditions of Northern Italy also exacerbate air pollution. They add that it is more able to stagnate there than in other parts of the country.
Dysregulated immune systems
A correlation between air pollution and COVID-19 lethality does not necessarily mean that one causes the other. The researchers detail other factors that may link air pollution to the relative lethality of the disease.
Previous research on other diseases that result in acute respiratory distress syndrome makes clear that these illnesses become significantly worse when immune system dysregulation causes inflammation in different parts of the body.
Further, the authors point out that “Air pollution represents one of the most well-known causes of prolonged inflammation, eventually leading to an innate immune system hyper-activation.”
A 2016 study identified this type of inflammation in healthy young people who do not smoke. Another research article linked it to the length of exposure a person has to air pollution.
In addition to this, air pollution damages the cilia in a person’s lungs. Cilia, which are microscopic, hair-like organelles, are one of the first lines of defense against airborne infection.
Although the authors believe that air pollution may contribute to the higher number of deaths from COVID-19 in Lombardy and Emilia Romagna, they stress that it is not the whole story.
Scientists need to carry out further research to determine the significance of air pollution and to understand better the other factors that may affect the lethality of the virus.
As Dr. Dario Caro, an environmental scientist in the Department of Environmental Science at Aarhus University in Denmark, explains, “Our considerations must not let us neglect other factors [that may be] responsible for the high lethality recorded.”