Sustainable policies for air pollution reduction after COVID-19 pandemic: Lessons learnt from the impact of the different lockdown periods on air quality

Due to the COVID-19 pandemic, governments imposed several mobility restrictions which can be used to evaluate their impact on air quality and generate better-targeted policies to improve it. Therefore, this study aimed to define sustainable mitigation measures to reduce air pollution based on quantifying the impacts of the restrictions imposed during the COVID-19 pandemic on air quality in Portugal. Thus, hourly concentrations of PM10, PM2.5, NO2, O-3, CO and SO2 were obtained from the Portuguese Air Quality Monitoring Network. Data was then divided into six periods (2020-2021) and compared with the corresponding historical periods (2015-2019). Furthermore, the satellite data of NO2, CO, and absorbing aerosol index (AAI) from the sentinel-5P TROPOMI was collected to complement the analysis conducted for the monitoring data. Overall, air quality improved in all study periods and areas, except in industrial sites. The satellite data corroborated the results herein achieved and thus validated the real effect of the measures adopted in the country during the pandemic on air quality. Sustainable policies to improve air quality could include remote (or hybrid) work whenever possible as a long-term measure and prohibition of travelling between municipalities when an extraordinary event of high air pollution is predicted or occurs. Other policies should be adopted for industrial areas. Given this, and as the restrictive mobility measures had a strong effect on reducing air pollution, the post-COVID era represents an opportunity for society to rethink future mobility and other emerging policies, that should favour softer and cleaner means of transportation