The impact of COVID-19 in air quality worldwide: a systematic review.

WHO had announced on the 11th of March that COVID-19 was considered a pandemic disease. At this stage, around 37 million cases and one million deaths were confirmed worldwide (in October 2020). To try to avoid the contagion of the population, all governments around the world had applied several social and hygienic recommendations, as well as mandatory measures. All of this had a huge impact not only on people's lifestyles but also on the environment. Based on PRISMA methodology, this study aims to identify the main impacts of coronavirus on air quality. Seven articles had accomplished all inclusion criteria and were deeply studied. In general, all air quality pollutants had decreased during the (partial) lockdown, showing a positive impact on air quality worldwide. In areas associated with urban traffic, the differences before/during lockdown became significant for the CO (-53.1%), PM10 (-22.8%), PM2.5 (-29.8%) and NO2 (-54.3%). Similar results were observed all around the world. Although this statement, the authors are aware of the extremely negative impact that all this situation has on the social and economic point of view. [ABSTRACT FROM AUTHOR]