Table 1.
Summary of results of recent reviews on the influence of air pollution of the transmission of SARS-CoV-2 and the incidence and severity of COVID-19.
| Topic of the Review | Main results and conclusions | Reference |
|---|---|---|
| To highlight the potential role of PMs in the spread of COVID-19 in Italian cities | **Long-term exposure and short-term exposure to high levels of pollutants are correlated to an increase in COVID-19 contagion. ** COVID-19 infection should be investigated in relation to ACE2 expression after PM exposure in order to verify the different susceptibility to infection by PM exposed and non-exposed cells. |
Comunian et al. (2020) |
| Potential link between compromised air quality and transmission of SARS-CoV-2 in affected areas of India | **Polluted environments can enhance the transmission rate of SARS-CoV-2 under moderate-to-high humidity conditions. | Manoj et al. (2020) |
| Effects of air pollution on COVID-19 infection and mortality | **Exposure to air pollution especially NO2 and PM2.5 may increase the susceptibility of infection and mortality from COVID-19. **Air pollution can cause adverse effects on the prognosis of patients affected by SARS-CoV-2 infection. |
Ali and Islam (2020) |
| To estimate the fraction of COVID-19 mortality that is attributable to the long-term exposure to ambient fine particulate air pollution | **Air pollution is an important cofactor increasing the risk of mortality from COVID-19. | Pozzer et al. (2020) |
| The role of air pollution in COVID-19 spread and lethality | **Important contribution of chronic exposure to air pollution on the COVID-19 spread and lethality. ** PM2.5 and NO2 would be more closely correlated to COVID-19 than PM10. |
Copat et al. (2020) |
| Association between the level of ambient air pollution and COVID-19 | **PM exposure could weaken and dysregulate immune response, resulting in a failure to defend against virus invasion. **PM exposure could cause ACE2 overexpression to increase viral load during invasion. **Airborne PM could increase transmission distance of SARS-CoV-2. |
Wang et al. (2020) |
| Impact of outdoor air pollution on COVID-19: evidence from in vitro, animal, and human studies | **Both short- and long-term exposures to air pollution may be important aggravating factors for SARS-CoV-2 transmission and COVID-19 severity and lethality through multiple mechanisms. | Bourdrel et al. (2021) |
| To summarize knowledge on SARS-CoV-2 transmission pathways | **The results suggest the influence of certain underestimated factors on the environmental behavior and survival of the SARS-CoV-2. **Outdoor risk sources such as aerosolized particles emitted during wastewater treatment and particulate matter, both of which may act as virus carriers, should be carefully assessed. |
Senatore et al. (2021) |
| How outdoor pollution exposure could potentially affect the viral life cycle of SARS-CoV-2 and pathogenesis of COVID-19 | **Exposure to NO2, O3 and particulate matter could predispose exposed populations toward developing COVID-19-associated immunopathology, enhancing virus-induced tissue inflammation and damage. | Woodby et al. (2021) |
| Potential impact of air pollution on COVID-19 incidence and deaths. | **Both long-term and short-term air pollution may play an important role in the airborne spreading of SARS-CoV-2 and may enhance the severity of COVID-19. **Exposure to NO2 and PM2.5 was more often correlated with COVID-19 infections and mortality than PM10. |
Ali et al. (2021) |
| Acute and chronic exposure to air pollution in relation with incidence, prevalence, severity and mortality of COVID-19 | **Short-term and long-term exposures to PM2.5, and long-term exposure to NO2 appear to be most consistently associated with COVID-19. O3 only for incident cases. **Studies assessing the effects of acute exposures presented substantial risks of bias. |
Katoto et al. (2021) |
| Role and potential association of air pollution especially particulate matter pollution in the transmission of COVID-19. | **There appears to be a positive role of atmospheric particulate matter (PM) pollution and the spread of COVID-19. **Some studies propose that PM operates as a virus carrier, promoting its transport through the air. **Exposure to ambient PM may reduce the resistance to infection in the population. |
Maleki et al. (2021) |
| Possible transmission routes of COVID-19 and different mutations of the virus via environmental media | ** Particulate matter may be a carrier for SARS-CoV-2. **More investigations should be undertaken focusing on the environmental transmission pathways of virus, which could contribute to the prevention and control of the COVID-19 epidemic. |
Shao et al. (2021) |
| To review the role of PMs in the spread of COVID-19, as well as the relationship among COVID-19, PMs, and angiotensin-converting enzyme 2 (ACE2) | **There is scientific evidence on the correlation between PM levels and the spread of SARS-CoV-2. **ACE2 plays a very significant role in COVID-19 |
Khan et al. (2021) |
| Influence of air pollution and climate indicators on COVID-19. | **Air pollution and meteorological parameters have critical effects on the rate of propagation and severity of COVID-19 cases. **The mechanisms may include air pollution-mediated comorbidities, airway damage, pulmonary epithelial permeability, inflammatory and immune dysregulation, metabolic pathway and pollution-induced overexpression of ACE-2 receptor. |
Zhao et al. (2021) |
| Potential relationship of PM with several life-limiting human diseases and COVID-19 | **PM exposure could be related as a carrier for SARS-CoV-2 transmission and COVID-19 infection. **Oxidative stress and inflammatory responses are considered as the major mechanism involved in the PM induced adverse effects. |
Zhu et al. (2021) |
| To review the cumulative effects of ambient PM2.5-exposure and SARS-CoV-2 transmission on exacerbating cardiopulmonary outcomes | **Exposure to air pollution increases susceptibility to COVID-19 infection, creating a pre-inflammatory state in patients. **Air pollutants affect respiratory and cardiovascular health, COVID-19 prognosis and mortality are impacted by the presence of respiratory and cardiovascular comorbidities. **Chronic exposure to air pollution increases inflammation in populations that are thus more susceptible to contracting the coronavirus. |
Lai et al. (2021) |
| To review literature focused on the transmission of SARS-CoV-2 in the spread of COVID-19 and present an environmental perspective on why airborne transmission has not been very conclusive so far | **One of the reasons for reduced emphasis on airborne transmission could be that the smaller droplets have a smaller number of viruses as compared to larger droplets. ** Small droplets containing SARS-CoV-2 might also physically combine with or attach to pre-existing PM so that their behavior and fate may be governed by PM composition. |
Ram et al. (2021) |