TABLE 1.

Research questions on air pollution as a contributing factor to COVID 19 infection

Research question	Certainty vs. uncertainty
Is SARS‐CoV‐2 exhaled?	Yes
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.