question: On March 16, 2020, Kolkata megacity in India announced partial lockdown due to COVID-19 crisis. This study presents an analysis for multiple pollutants with special focus on NO2 and O3 based on data from different monitoring stations located to across Kolkata city for the period from 16 March-17 May 2020 compared to the pre-lockdown period. Most significant reduction was observed in the concentration of nitrogen dioxide (NO2) (- 76.8%), volatile organic compounds (VOCs) (- 69.5%), PM10 (- 64.6%) and PM2.5 (- 60.9%). A lower reduction percentage was found for CO, sulfur dioxide (SO2) and ammonia (-48.6%, - 41.7% and – 41.1% respectively). However, during partial lockdown, lockdown phase-1, phase-2 and phase-3, surface-level ozone (O3) has changed respectively by 31.72%, 31.13%, -14.28% and -14.05% which resulted in an overall increase of 8.17% in the entire study period. The air quality index (AQI) in Kolkata which usually remains poor or very poor, even during lockdown period, failed to attain the ‘good’ standard. This needs special attention in human health impact assessment and public health management. We recommend additional attention to be drawn towards stickiness in O3 which had adverse human health and which went up during lockdown period compared to pre-lockdown period. We highlight some major policy implications of the observed trends to combat city air pollution along with climate co-benefits by shifting transport fuel and related infrastructure. © 2022 World Research Association. All rights reserved.