Preliminary results of COVID-19 restriction measures on the air pollution levels in the city center of Athens, Greece

COVID-19 is evolving into one of the worst pandemics in recent history. The lockdown measures implemented worldwide to slow the spread of the COVID-19 pandemic have caused an unprecedented reduction in global economic activity. Strict lockdown measures came into force in Greece from March 23th 2020. This study aims to assess the changes in air pollution levels during the restriction measures in Athens, the city with the most COVID-19 cases in the whole country. Measurements in a central location during the lockdown (24/03/2020 -07/04/2020) were compared with levels during the pre-lockdown (19/02/2020 -11/03/2020) period. Urban air pollution markedly decreased but with substantial differences among pollutants. The most significant impact during the lockdown period was observed for the concentrations of carbon monoxide (CO) and nitrogen oxides (NOx) with reduction percentages of -47% and - 35%, respectively, compared to the pre-lockdown period. These air pollutants are mainly related to traffic emissions. A lower reduction was recorded for coarse particulate matters (PM10) (-24%), probably due to the existence of other local sources of emission along with secondary formation. Nevertheless, this result must be further examined in order to be interpreted. Additionally, meteorological parameters such as wind speed found to play a key role on the results as most air pollutants were negatively correlated with higher air velocities. The scope of this study is to provide short term air quality results to the existing literature, in order to enhance decision making on life quality improvement in respect to the urban environment.