Table 1 Association between short-term exposure to air pollution and risk, severity, incidence, and lethality for COVID-19 Pandemic

Yao Y et al. [52], June 2020

*Associations between PM and COVID-19 CFR

*49 Chinese cities, spatial analysis

CFR

Pollutants (10 μg/m³ increase in and concentrations)- COVID-19 CFR increased by:

*Epidemic period:

• PM_2.5: 0.24% (0.01–0.48%) and

• PM₁₀: 0.26% (0.00–0.51%), respectively.

PM distribution and its association with COVID-19 CFR suggests that exposure to such may affect COVID-19 prognosis.

Frontera A et al. [14], August 2020

*Relationship between air PM_2.5 and NO₂ and COVID-19, Italian regions.

Transmission, number of patients, severity of presentation and number of deaths.

*Correlations between mean PM_2.5:

• Total number cases: r = 0.64; p = 0.0074,

• ICU admissions per day: r = 0.65; p = 0.0051,

• Deaths: r = 0.62; p = 0.032

• Hospitalized cases: r = 0.62; p = 0.0089

*Highest cases, more severe cases and two-fold mortality of COVID-19 in the most polluted regions

Li H [57] et al., August 2020

Retrospective study, correlation between COVID-19 incidence and AQI, Wuhan and XiaoGan between January 26th to February 29th in 2020

Incidence

* Pollutants-COVID-19 Incidence (Wuhan vs XiaoGan: R2):

• PM_2.5: 0.174 vs 0.23

• PM₁₀: 0.105 vs 0.158

• NO₂: 0.329 vs 0.158

• CO: 0.203 vs 0.022

*AQI-COVID-19 Incidence (Wuhan vs XiaoGan: R²):

0.13, p < 0.05 vs 0.223, p < 0.01).

AQI, PM_2.5, NO₂, and temperature are four variables that could promote the sustained transmission of COVID-19.

Zoran M et al. [58], October 2020

Time series of daily average inhalable gaseous O₃ and NO₂, in Milan, Lombardy in Italy, January–April 2020

Transmission and lethality

O₃ vs NO₂ (January–April 2020)-COVID-19:

• Total number: r = 0.64 **vs − 0.55**

• Daily New positive: r = 0.50** vs − 0.35**

• Total Deaths cases: r = 0.69 vs − 0.58**

* O₃ can acts as a COVID-19 virus incubator.

*Estimates can be attributed to airborne bioaerosols distribution.

Zhu Y et al. [59], Jully 2020

Daily confirmed cases, air pollution concentration and meteorological variables in 120 cities were obtained from January 23, 2020 to February 29, 2020 in China.

Incidence

*10-μg/m³ increase (lag0–14) associated with increase in the daily counts of confirmed cases:

• PM_2.5: 2.24% (95% CI: 1.02 to 3.46),

• PM₁₀: 1.76% (95% CI: 0.89 to 2.63),

• NO₂:6.94% (95% CI: 2.38 to 11.51),

• O₃: 4.76% (95% CI: 1.99 to 7.52)

*10-μg/m³ increase (lag0–14) associated with a decrease in COVID-19 confirmed cases.

SO₂: 7.79%: (95% CI: − 14.57 to − 1.01)

Significant relationship between air pollution and COVID-19 infection, which could partially explain the effect of national lockdown and provide implications for the control and prevention of this novel disease.

Adhikari A et al. [60], Jun 2020

Associations between O₃, PM_2.5, daily meteorological variables and COVID-19 in Queens county, New York during March–April 2020

Incidence and mortality

*Pollutants (lag 0–21)-New COVID-19 Cases

• PM_2.5: IRR: 0.6684 (0.6478–0.6896), P < 0.0001

• O₃: IRR: 1.1051 (1.0747–1.1363), P < 0.0001

*Pollutants (lag 0–21)-New COVID-19 Deaths

• PM_2.5: IRR: 0.8912 (0.7966–0.9971), P < 0.0444

• O₃: IRR: 0.8958 (0.8072–0.9941), P < 0.0382

Short-term exposures to O₃-8h + other meteorological factors can influence COVID-19 transmission and initiation, but aggravation and mortality depend on other factors.

Chakraborty P et al. [61], July 2020

*Effects of COVID-19, on a large population persistently exposed to various pollutants in different parts of India.

*Data, from online resources,

Fatality

*NO₂ from vehicular emission and absolute number of COVID-19:

• Deaths: r = 0.79, p < 0.05

• Case fatality rate: r = 0.74, p < 0.05.

*Rise in NO₂/ PM_2.5 ratio increased the COVID-19 CFR by: 7.2%

Homeless, poverty-stricken, hawkers, roadside vendors, and others regularly exposed to vehicular exhaust, may be at a higher risk in the COVID-19 pandemic.

Bontempi E [30], July 2020

PM₁₀ situation in Lombardy (from 10th February to March 27, 2020), several days before the sanitary emergency explosion; comparison: the situation of Piedmont, located near to the Lombardy

Incidence

Piedmont cities, presenting lower detected infections cases in comparison to Brescia and Bergamo in the investigated period, had most sever PM₁₀ pollution events in comparison to Lombardy cities.

Not possible to conclude that COVID-19 diffusion mechanism also occurs through the air, by using PM10 as a carrier.

Bashir MF et al. [62], May 2020

Secondary published data from the Centers for Disease Control and the EPA (March–April 2020) to assess the relation between environmental pollution determinants and the COVID-19 outbreak in California.

Incidence, Mortality

*Pollutants-COVID-19 Cases

• PM₁₀: r = − 0.375**

• PM_2.5: r = − 0.453***

• SO₂: r = − 0.426***

• CO: r = 0.083

• VOC: r = 0.054

• Pb: r = 0.178**

• NO₂: r = − 0.736***

*Pollutants-COVID-19 Deaths

• PM₁₀: r = − 0.350**

• PM_2.5: r = − 0.429***

• SO₂: r = − 0.397**

• CO: r = 0.123

• VOC: r = 0.038

• Pb: r = 0.174**

• NO₂: r = − 0.731***

Useful supplement to encourage regulatory bodies to promote changes in environmental policies as pollution source control can reduce the harmful effects of environmental pollutants

Bolaño-Ortiz TR et al. [63], July 2020

Correlation between air pollution indicators (PM₁₀, PM_2.5, and NO₂: day 0–14 prior COVID-19 test) with the COVID-19 daily new cases and deaths in Latin America and the Caribbean region

Transmission and mortality

Spearman rank correlation tests:

Mexico City (Mexico), PM_2.5, PM₁₀, NO₂

• New Cases: − 0.214*, − 0.327**, − 0.206

• Total Cases: − 0.124, − 0.444***, − 0.446***

• Mortality: − 0.256**, − 0.395***, − 0.462***

San Juan (Puerto Rico), NO₂:

• New Cases: 0.367***

• Total Cases: 0.636***

• Mortality: − 0.194

Bogotá (Colombia), PM_2.5, PM₁₀, NO₂

• New Cases: − 0.414***, − 0.150, 0.009

• Total Cases: PM₁₀, NO₂: − 0.438***, − 0.190

• Mortality: 0.050, 0.097, 0.182

Santiago (Chile), PM_2.5, PM₁₀, NO₂

• New Cases: 0.466 ***, 0.351***, 0.547***

• Total Cases: 0.481***, 0.353***, 0.547***

• Mortality: 0.478***, 0.404 ***, 0.569 ***

São Paulo (Brazil) PM_2.5, PM₁₀, NO₂

• New Cases: 0.350***, 0.354***, 0.506***

• Total Cases: 0.261, 0.277, 0.337***

• Mortality: 0.203, 0.228*, 0.354***

Buenos Aires (Argentina). PM₁₀, NO₂

• New Cases: 0.414, 0.274

• Total Cases: 0.434***, 0.195

• Mortality: 0.157, 0.056

*COVID-19 infection rate correlation, in particular for the Gini index of each country (r = 0.51,p < 0.13), the urban poverty rate (r = − 077,p = 0.01) and the urban extreme poverty rate (r = 0.79, p = 0.01).

*Income inequality and poverty levels in the cities analysed related to the spread of COVID-19 positive and negative, respectively.

Borro M et al. [13], August 2020

* PM_2.5 and COVID-19 outcomes from 20 February-31 March 2020 in 110 Italian provinces

*Bioinformatic analysis of the DNA sequence encoding the SARS-CoV-2 cell receptor ACE-2

Incidence, CFR, Mortality

*PM2.5 levels and COVID-19

• Incidence: r = 0.67, p < 0.0001)

• Mortality rate: r = 0.65, p < 0.0001

• CFR: r = 0.7, p < 0.0001)

*Bioinformatic analysis of the ACE-2 gene identified nine putative consensus motifs for the aryl hydrocarbon receptor.

*Confirm the supposed link between air pollution and the rate and outcome of SARS-CoV-2 infection

*Support the hypothesis that pollution-induced over-expression of ACE-2 on human airways may favor SARS-CoV 2 infectivity

Raciti L et al. [53], Jun 2020

To assess the relationship between volcanic ash pollution and COVID-19 in Sicily, Italy

Incidence

Volcanic gases and heavy metals-related air pollution, combined to specific climatic conditions and regional topography, in favouring severe COVID-19 diffusion in Sicily

Clinical and epidemiological studies are needed to support the hypothesis

Jiang Y et al. [64], 2020 August

Retrospective study of ambient air pollutant concentrations (daily average), and meteorological variables data of Wuhan, Jan 25 and April 7, 2020 in relation to COVID-19

Death Number

*Pollutants-COVID-19 Deaths (RR, 95%CI, p-value):

• PM_2.5: 1.079, 1.071–1.086, < 0.01

• PM₁₀: 0.952, 0.945–0.959, < 0.01

• SO₂: 0.951, 0.919–0.984, < 0.01

• CO: 0.177, 0.131–0.24, < 0.01

• NO₂: 1.002, 0.996–1.007, 0.55

• O₃_8h: 1.001, 0.998–1.003, 0.56

PM_2.5 and diurnal temperature range are tightly associated with increased COVID-19 deaths.

Filippini T et al. [55], October 2020

Collection of NO₂ tropospheric levels using satellite data available at the European Space Agency before the lockdown in association with COVID-19 at different time (March 8, 22 and April 5), in the 28 provinces of Lombardy, Veneto and Emilia-Romagna (Italy).

Prevalence rate

*Little association of NO₂ levels with COVID-19 prevalence up to about 130 μmol/m2

*Positive association, evident at higher levels at each time point.

Notwithstanding the limitations of the use of aggregated data, these findings lend some support to the hypothesis that high levels of air pollution may favour the spread of the SARS-CoV-2 infection.