key: cord-0849221-vxy4s0bw authors: Annesi‐Maesano, Isabella; Maesano, Cara Nichole; D’Amato, Maria; D’Amato, Gennaro title: Pros and cons for the role of air pollution on COVID‐19 development date: 2021-06-04 journal: Allergy DOI: 10.1111/all.14818 sha: e7113a9aea0250063dc5e3fe30f88fd158f13452 doc_id: 849221 cord_uid: vxy4s0bw As SARS-CoV-2 has spread across the globe, it has been difficult to ignore patterns suggesting that regions with poor air quality are witnessing disproportionate impacts in terms of the frequency and severity of COVID-19 infection. Consequently, researchers have rightly recognized the importance of considering the role of air pollution inthe COVID-19 pandemic.Here, we discussthe pros and cons of air pollution as a contributing factorto COVID-19,according to existing research questions (Table 1). At the general population level, COVID-19 hospitalizations and However, no significant impact of air pollution on COVID-19 was found in other zones also highly polluted (eg, Athens, London, Qatar). This may depend on fact that SARS-CoV-2 infection is multifactorial. Two patterns seem possible 2 ( Figure 1 ). On the one hand, air pollution may render people more susceptible to infection by SARS-CoV-2. It is well established that gases such as nitrogen dioxide (NO 2 ) or ozone (O 3 ) and respirable PM may modify airways permeability. In particular, exposure to either fine or ultrafine particles including Is SARS-CoV-2 airborne? Yes: evidence has accumulated that the majority of transmissions occur as a result of infected people spewing large droplets and small particles called aerosols when they cough, talk, sing, or breathe. Is SARS-CoV-2 found in PM aerosols? Potentially, as it can be carried by or mixed with secondary aerosols Is SARS-CoV-2 viable once in suspension? Yes, but needs to be confirmed Is air pollution a co-factor of SARS-CoV-2 infection? Yes, based on several mechanisms. Additionally, a link has already been observed in the cases of SARS, influenza, syncytial virus and measles. Is COVID-19 significantly related to air pollution? Potentially yes, but additional ad hoc data are needed. In addition, the mechanisms are not understood. The role of airborne SARS-CoV-2 transmission due to small respiratory droplets of diameter <5 µm emitted by symptomatic as well as asymptomatic, but infected, individuals at the origin of droplet nuclei remaining suspended in the air is, however, still challenged by a lack of studies. A major drawback in this respect is that the minimum infectious dose, as expressed in viral RNA copies necessary to promote the infection, is not yet defined. In addition, very few studies so far have assessed RNA copies in outdoor air and they are not conclusive. In a Chinese study, the observed RNA concentrations were above the detection limits only in crowded areas. 8 In Italy, a study also observed detectable SARS-CoV-2 RNA in congested zones, but not in less polluted zones (below 10 µg/m 3 in mean). 9 aerobiology, COVID, SARS-CoV The authors have nothing to disclose. Isabella Potential role of particulate matter in the spreading of COVID-19 in Northern Italy: first observational study based on initial epidemic diffusion The impact of outdoor air pollution on COVID-19: a review of evidence from in vitro, animal, and human studies Regional and global contributions of air pollution to risk of death from COVID-19 It is time to address airborne transmission of coronavirus disease 2019 (COVID-19) Aerosol and surface stability of SARS-CoV-2 as compared with SARS-CoV-1 Peaks of fine particulate matter may modulate the spreading and virulence of COVID-19 Pollen exposure weakens innate defense against respiratory viruses Aerodynamic analysis of SARS-CoV-2 in two Wuhan hospitals SARS-CoV-2 concentrations and virus-laden aerosol size distributions in outdoor air in north and south of Italy SARS-Cov-2RNA found on particulate matter of Bergamo in Northern Italy: First evidence Methodological considerations for epidemiological studies of air pollution and the SARS and COVID-19 coronavirus outbreaks