The pandemic caused by coronavirus COVID-19 is having a worldwide impact that affects health and the economy and indirectly affects air pollution in cities. In Spain, the effect has evolved from being anecdotal in January 2020 to become the second country in Europe with the highest number of cases (614,000 cases by 17/09/2020), which has affected the health system and caused major mobility restrictions. In contrast, COVID-19 has affected air pollution and energy consumption in the country. This article analyzes the indirect effect produced by this pandemic on air pollution, referenced to various stages that occurred in Spain: first stage, without public awareness of COVID-19 impact (mid-January 2020); second is when Spanish Government alerted (late February 2020); and third, after the decree of alarm and mobility restriction of citizens by the government (March 2020) along with the various phases of the de-escalation. The indirect effect produced by this pandemic on air pollution in Spanish cities has been resulted in a decrement of 70% to 80% of average, taking into account dates after the decree of alarm and mobility restriction by the Spanish government (14/03/2020), compared to days prior to that date. Thus, the results of this analysis indicate a significant alteration in air pollutants; these alteration patterns have followed similar paths over different countries worldwide improving the air quality as discussed by Dutheil et al.

<p>The human effect on air quality in cities and the evolution of air pollution is obvious, due to economic activity, vehicle traffic, etc. The situation created indirectly by COVID-19, has caused many countries to impose during certain periods restriction of movement and stoppage of economic activities, which has allowed us to observe the instant effect that occurs on the air quality in cities. This article discusses what the observed effect has been, focusing on the early moments of the pandemic (January 2020 to March 2020), with an analysis of the situation from its origin in China to its arrival in Europe and more specifically the situation created in Spain. After the analysis of the situation, it can be seen the large reduction of pollutants in the air of different cities, and in particular in Spain, which came to reduce about 80%. All this leads us to the observation of how human activity can greatly influence air pollution.</p>