Watch out for trends: did ozone increased or decreased during the COVID-19 pandemic?

Abstract

Restriction measures against COVID-19 caused the environmental panorama of cities to change, especially in relation to air pollution. This scenario of severe reduction in the emission of air pollutants led to a flurry of studies about their behavior during the pandemic. The vast majority of studies pointed to a decrease in all pollutants, with the exception of ozone. However, was this highlighted ozone trend really the global trend? This discussion seeks to answer this question while addressing two major considerations that led to this trend: (1) the process of ozone formation and behavior and (2) the main reasons that led to the findings of this trend (region of the studies, meteorological conditions, and the time scale adopted for data collection). From our observations, we emphasize that a trend is not unanimity! The global trend turned out to be the opposite of what the initial studies showed, all this because the observed trend was a regional trend, affected by the reasons discussed. Thus, we raise awareness and concern with the way in which the initial “fever” of the behavior of air pollutants occurred and also toward the act of sampling highly populated areas, as this attitude could have caused biased estimations and disinformation.Graphical abstract