The air quality in Kerala's commercial hub Kochi was worse last year compared to 2020 as the number of good "AQI (air quality index) days" was lesser, according to a recent study. Analysis of days as per AQI categorisation showed that Kochi city has not been able to sustain the air quality gains of 2020, said the air pollution analysis of southern state, released by the Centre for Science and Environment (CSE).