Are there medium to short-term multifaceted effects of the airborne pollutant PM determining the emergence of SARS-CoV-2 variants?

The COVID-19 pandemic has been characterised by successiveoutbreaks effecting large swathes of the world's populations. These waves of infection have been mainly driven by a number of more transmissiblevariants which appear to evade the populations' immunity gained from previous outbreaks. There appears to be a link between COVID-19 and a ubiquitous airborne pollutant calledparticulate matter, PM2.5. Particulate matter through a number of mechanisms, including its anthropogenic effect, appears to be associated with the incidence and the mortality related to the COVID-19 pandemic. This paper poses a number of hypotheses on the short to medium-term mechanisms whereby PM2.5 may be party to the natural selection of SARS-CoV-2 virus, with the consequent emergence of variants.