Comparison of Air Quality in Kathmandu, Nepal before and during COVID-19 Lockdown

Abstract

Abstract A lockdown strategy was adopted to control COVID-19 transmission in Nepal. We investigated the possible impacts of lockdown on air pollution ( PM2.5, and O3 ) levels and trends before and during the COVID-19 lockdown period in Kathmandu Valley. Secondary data from seven air quality monitoring stations in Kathmandu Valley was obtained from starting of 2018 to mid-June of 2020. The nonparametric linear regression slope (Theil-Sen slope) and Mann Kendall test for significant trends over time were applied to assess the air pollution levels and trends. Both PM2.5 and O3 levels showed cyclic and seasonal variations. PM2.5 peaked in winter, while the O3 level had a significant peak in the spring and summer seasons. PM2.5 and O3 concentrations decreased significantly during the lockdown period compared to the same period of the previous years by 31.66% and 8.17%, respectively. Theil-Sen slope estimates showed a statistically significant declining monthly average level of PM2.5 μg m-3 (-9.55; 95CI: -15.87; -5.26; p <0.001) and O3 μg m-3 (-1.68; 95CI: -3.22; -0.01; p <0.01), respectively. The decline in air pollution levels is likely due to the lockdown, including travel restrictions and industrial shutdowns. While the lockdown policy seems to curb air pollution, there is an economic burden associated with it. The government should consider policies such as introducing electric vehicles, vehicle restriction, and congestion charges, encouraging electricity-based cooking and increasing investment in bicycle lanes and public transportation to curb air pollution in Kathmandu Valley.