For the second day in a row, Mumbai's air quality was worse than Delhi's, as a thick layer of smog covered the city. On Wednesday, Mumbai's PM10 (particulate material) level was 143, while Delhi's was 122. The Air Quality Index (AQI) between 201 and 300 is considered poor, and any value above 300 is classified as very poor, according to the Indian Institute of Tropical Meteorology's System of Air Quality and Weather Forecasting and Research (SAFAR). By Thursday evening, Mumbai's PM10 level had increased to 154, while Delhi's remained lower at 119, as reported by the Maharashtra Pollution Control Board., Mumbai News, Times Now