Table 1.
Summary of the main discussed findings underling the relationship between high levels of air pollutants and increased risk/fatality of SARS-CoV-2 infection.
| Area of The Study | Size of Population | Air Pollutants | Effect on COVID-19 | Reference |
|---|---|---|---|---|
| * China (for SARS-CoV-1) | >5000 cases of SARS-CoV-1 leading to nearly 350 fatalities | Air pollution evaluated by air pollution index (API) | In parts of China with moderate levels of air pollution, the risk of dying from the disease was >80% higher compared with areas with relatively clean air, and in heavily polluted regions the risk was twice as high | Cui et al., 2003 [178] |
| China | 213 cities | Air pollution | Temporal increases in COVID-19 cases were associated with short-term variations in ambient air pollution | Zhu et al., 2020 [179] |
| China | 120 cities | PM2.5, PM10, CO, NO2, and O3 | A statistically significant relationship between short-term exposure to higher air pollutants (PM2.5, PM10, CO, NO2, O3) and increased risk of SARS-CoV-2 infection | Zhu et al., 2020 [179] |
| Italy | All Italian regions (n = 104,212 total number of cases) | NO2 and PM2.5 | - Correlation between PM2.5 and COVID-19 outbreak distribution was observed - The highest number of COVID-19 cases were recorded in the most polluted regions, with patients presenting with more severe forms of the disease requiring ICU admission. In these regions, mortality was two-fold higher than the other regions despite similar rates of ICU admission (crude death rate 14% vs. 7%) - Chronic exposure to PM 2.5 caused alveolar ACE2 receptor overexpression |
Frontera et al., 2020 [197] |
| Italy | Northern area: 71 provinces including Bergamo, Brescia, and Milan | Chronic exposure (PM10, PM2.5, NO2, and O3) | Higher mortality correlated with poor air quality, namely, with high PM2.5, NO2, and O3 values | Fattorini and Regoli 2020 [184] and Conticini et al., 2020 [185] |
| Italy | 110 provinces | PM2.5 |
- There was a correlation between air pollution and the rate and outcome of SARS-CoV-2 infection. - Support the hypothesis that pollution-induced over-expression of ACE2 on human airways may favour SARS-CoV-2 infectivity |
Borro et al., [163] |
| United States (USA) | A cross-sectional study nationwide | NO2, PM2.5, O3 | There was an Estimated association between long-term (2010–2016) county-level exposures to NO2, PM2.5, and O3 and county-level COVID-19 case-fatality and mortality rates | Liang et al., 2020 [175] |
| USA | More than 3000 counties (representing 98% of the population) | Air pollutants—PM2.5 | - Significant overlap between the causes of death in COVID-19 patients and those that lead to mortality from PM2.5 - An increase of 1 μg/m3 in PM2.5 was associated with an 8% increase in the COVID-19 mortality rate. |
Pozzer et al., 2020 [162] and Wu et al., 2020 [186] |
| USA | From the environmental protection agency (EPA) website | O3, NO2, CO, and SO2 | Ground-level O3 and NO2 concentrations contributed to a greater COVID-19 mortality rate | Liu and Li 2020 [161] |
|
Several countries: China, Iran, Italy, Spain, France, Germany, the United Kingdom, and USA. |
Both infections and deaths due to COVID-19 were collected and normalised by population size per administration unit (100,000 residents) | Associating several annual satellite and ground indexes of air quality (PM10, PM2.5, SO2, CO, NO2, and O3) | - Statistically significant positive correlations between COVID-19 infections and a high level of air pollution (long-term exposure) in each country was reported. - The higher mortality was correlated with poor air quality, namely, with high PM2.5 and NO2 values |
Pansini and Fornacca 2020 [182] |
| Italy and England | - Northern Italy - UK Biobank data (cohort of 1450 subjects) |
NO2 | NO2 correlated with mortality rates. | Ogen et al., 2020 [187], Travaglio et al., 2020 [189], and Filippini et al., 2021 [188] |
| Spain | 372 of the 378 Basic Health Areas in Catalonia (population 371–72,321 inhabitants, mean 20,266) | NO2 and PM10 | Association was found between long-term exposure to air pollutants and an increased risk of incidence and death from COVID-19: exposure to NO2 and, to a lesser extent PM10 were independent predictors of the spatial spread of COVID-19 | Saez et al., 2020 [166] |
| Mexico | Metropolitan Mexico city. Pediatric and young adult onset of Alzheimer’s diseases | Nanoparticles (NPs) | In a worst-case scenario, SARS-CoV-2 and NPs may exacerbate the adverse health effects also on the central nervous system | Calderon-Garciduenas et al., 2020 [194] |
* This study has been included as the first and high cited observation showing air pollution association and increased fatality of SARS patients in a Chinese population. Abbreviations: ICU, Intensive Care Unit.