Fig. 4From: Air quality index variation before and after the onset of COVID-19 pandemic: a comprehensive study on 87 capital, industrial and polluted cities of the worldPercentage change of AQI PM2.5, PM10, NO2 and SO2 between 2020 during the lockdown period and 2019 and 2021 in different cities in the world. A AQI-PM2.5 variation, B AQI-PM10 variation, C AQI-NO2 variation and D AQI-SO2 variationBack to article page