Delhi's PM2.5 levels met the national ambient air quality standard (NAAQS) on 154 days in 2023, according to the Center for Research on Energy and Clean Air. However, the PM2.5 concentration breached the norm on 211 days last year. Delhi recorded the highest number of 'satisfactory' days at 127 since 2016. The number of 'severe' pollution days increased in 2023 compared to 2022. The annual PM2.5 concentration in 2023 was 101 micrograms per cubic meter, higher than the previous year.