Air pollution appears to have a very close connection with the seriousness of Covid-19.
This is confirmed by a study carried out by Emory University in Atlanta, published in the scientific journal The Innovation (Cell group).
The researchers analysed the main urban air pollutants, including fine particulate matter (PM2.5), nitrogen dioxide (NO2) and ozone (O3), in 3076 counties in the United States (out of the 3142 in total) from January to July, and compared this data to the effects of Covid-19 in their resident populations.
In particular, they examined the mortality rate (i.e. the number of deaths of those diagnosed with Covid-19) and also the number of deaths caused by Covid-19 as a ratio of the population.
They discovered that, among the analysed pollutants, nitrogen dioxide showed the strongest correlation with the number of deaths due to Covid-19. According to the researchers, an increase of 4.6 parts per billion (ppb) of NO2 in the air can be associated with an 11.3 % increase in the Covid-19 case-fatality rate, whereas the number of deaths due to the coronavirus compared to the population rises by 16.2%.
In contrast, according to the researchers, a reduction of 4.6 ppb of NO2 in the US counties may have been able to prevent 14,672 deaths (out of a total of 138,552) among those who had tested positive for the virus.
Nitrogen dioxide, as we know, is produced by all the high-temperature combustion processes (heating systems, vehicle engines, industrial combustion, etc.) and causes irritation in bronchial mucosa, in several cases altering respiratory function and bronchial reactivity (in the event of prolonged exposure to high concentrations of NO2).
On the other hand, the researchers from Emory University observed no significant associations between exposure to PM2.5 fine particulate matter and the mortality rate of people affected by Covid, and found no noteworthy associations with ozone.
“The results of our study”, write the researchers in The Innovation journal, “support targeted public health actions to protect residents from Covid-19 in heavily-polluted regions with historically-high NO2 levels. The continuation of current efforts to lower traffic emissions and other ambient air pollution levels may be an important component of also reducing population-level risk of Covid-19 case-fatality and mortality”.
This study, we might add, also helps to explain why highly-polluted areas, like the area of Wuhan in China, or the vast open areas of the Pianura Padana in Italy, were the first to register particularly high numbers of Covid-patients, also with fatal outcomes.
A second study on the relationship between pollution and Covid-19 has also come out, conducted by Italian researchers (University of Bari and the National Institute of Nuclear Physics) and Russian researchers (State University of Tomsk), and published in the Environmental Pollution journal.
Their results are similar to those of Emory University in a general sense, but the details differ. According to this study, in fact, in addition to nitrogen dioxide, PM2.5 apparently also plays a significant role. The researchers used artificial intelligence, comparing the most-polluted areas in Italy with the mortality rate. In this way they discovered that the emissions of fine particulate matter associated with industry, farming and road traffic have a close connection with the seriousness of the illness, and can also predict its outcome: in the areas where the air quality is worse, Covid-19 will be more ferocious.