ABSTRACT
The Megacity of Delhi, home to 19 million inhabitants, is infamous for its poor air quality mainly due to anthropogenic emissions. While the COVID-19 pandemic is a health emergency, lockdown due to it saw an unprecedented decline in emission sources of pollutants by ~85%-90% in Delhi, resulting in sharp decline in the concentration of majority of pollutants. Here we report the experimental estimate of baseline level that is defined as the minimum level reached after lockdown under consistent fair weather condi-tion of major criteria pollutants. This may be consi-dered as an indicator of the background levels to which the population is chronically exposed. The con-sequences of such chronic air pollution exposure are excess respiratory and cardiovascular morbidity and mortality which are reported to be more serious than severe pollution episodes by epidemiologists. As the lockdown which was imposed on 24 March 2020, was extended during April and May, we present the pre-vailing ambient pollution levels and compare them with the baseline levels. Results are based on India’s largest monitoring network of 34 stations in Delhi. The findings are critical for policymakers to fine-tune ambient air quality standards and regulations leading to the development of effective risk management poli-cies and control strategies. © 2020. All rights reserved.