Effect of Lockdown on the Air Quality of Four Major Cities in Pakistan During the COVID-19 Pandemic

This study attempted to evaluate the effect of lockdown on the air quality of four major cities in Pakistan: Karachi, Lahore, Islamabad, and Peshawar. Particulate matter ( PM 2.5) concentration and U. S. Environmental Protection Agency Air Quality Index ( AQI) were used to determine air quality before and after lockdown. We found that air quality in all the cities improved after lockdown was imposed: PM 2.5 concentrations in Karachi and Lahore decreased by 62% and in Peshawar and Islamabad by 57% and 55%, respectively. AQI in Karachi and Islamabad improved from Unhealthy to Moderate and in Peshawar and Lahore from Unhealthy to Unhealthy for Sensitive Groups. Formal complete lockdown in Pakistan was imposed on March 24, 2020, and lasted until May 10, 2020, after which partial or smart lockdown was still in place. Maximum improvement in air quality was observed in April 2020, with concentrations starting to increase in May 2020 following the ease of r estrictions.