Air Pollution and Covid-19: The Role of Particulate Matter in the Spread and Increase of Covid-19's Morbidity and Mortality

Abstract

Sars-cov-2 virus (Covid-19) is a member of the coronavirus family and is responsible for the pandemic recently declared by the World Health Organization. A positive correlation has been observed between the spread of the virus and air pollution, one of the greatest challenges of our millennium. Covid-19 could have an air transmission and atmospheric particulate matter (PM) could create a suitable environment for transporting the virus at greater distances than those considered for close contact. Moreover, PM induces inflammation in lung cells and exposure to PM could increase the susceptibility and severity of the Covid-19 patient symptoms. The new coronavirus has been shown to trigger an inflammatory storm that would be sustained in the case of pre-exposure to polluting agents. In this review, we highlight the potential role of PM in the spread of Covid-19, focusing on Italian cities whose PM daily concentrations were found to be higher than the annual average allowed during the months preceding the epidemic. Furthermore, we analyze the positive correlation between the virus spread, PM, and angiotensin-converting enzyme 2 (ACE2), a receptor involved in the entry of the virus into pulmonary cells and inflammation.

Keywords: ACE2; covid-19; inflammation; oxidative stress; particulate matter.

Figure 1

Graphs showing the concentration values of PM10 (a) and PM2.5 (b) in Bergamo. The red line indicates the expected regulatory limit, while the blue line indicates the average in the two months analyzed (analysis processed with data collected by ARPA (Regional Environmental Protection Agency)).

Figure 2

Graphs showing the concentration values of PM10 (a) and PM2.5 (b) in Brescia. The red line indicates the expected regulatory limit, while the blue line indicates the average in the two months analyzed (analysis processed with data collected by ARPA).

Figure 3

Graphs showing the concentration values of PM10 (a) and PM2.5 (b) in Milano. The red line indicates the expected regulatory limit, while the blue line indicates the average in the two months analyzed (analysis processed by data collected by ARPA).

Figure 3

Graphs showing the concentration values of PM10 (a) and PM2.5 (b) in Milano. The red line indicates the expected regulatory limit, while the blue line indicates the average in the two months analyzed (analysis processed by data collected by ARPA).

Figure 4

(a) Graph showing a comparison between PM2.5 concentrations in Bergamo, Brescia, and Milan during January and February 2020. (b) COVID-19 positive’s growth in Bergamo, Brescia, and Milan from late February to late March 2020 (generated and modified from [46]).

Figure 4

(a) Graph showing a comparison between PM2.5 concentrations in Bergamo, Brescia, and Milan during January and February 2020. (b) COVID-19 positive’s growth in Bergamo, Brescia, and Milan from late February to late March 2020 (generated and modified from [46]).

Figure 5

Image showing the increase in the level of reactive oxygen species (ROS) owing to 90 min exposure to 5 μg/cm² of diesel pollution, detected by a fluorescent probe. * Statistically significant respect to control according to unpaired t-test, p < 0.05. Reproduced with the permission from [53].

Figure 6

Analysis of the pro-inflammatory interleukin (IL)8 cytokine release in A549 cells after exposure to ZnO (A) and CuO (B) nanoparticles alone or in combination with diesel exhaust particles. Statistically significant according to the unpaired t test; p < 0.05. * Reproduced with the permission from [52].

Figure 7

Differential staining of mouse bronchoalveolar lavage fluid (BALf) cells after PM1 intratracheal instillation. (a) Alveolar macrophages in the BALf collected 24 h post instillation from sham; (b) and (c) alveolar macrophages engulfing particles (square arrows) and infiltration of polymorphonuclear leukocytes (PMNs) (arrows) in the BALf collected 24 h after the last intratracheal instillation from PM1-treated mice. (a–c) bars = 50 µm. Reproduced with the permission from [56].