NEW DELHI: One hundred and three out of 130 cities covered under the National Clean Air Programme (NCAP) showed an improvement in the levels of PM10, one of the key pollutants, in 2024-25 compared to 2017-18, with Mumbai registering the highest decline of 44% among the six big metro cities, followed by Kolkata (37%), the environment ministry told the Lok Sabha on Monday.The data, shared in response to a Parliament Question, shows that Hyderabad and Bengaluru recorded a drop of 26% each, Delhi of 15%, and Chennai of 12% in the PM10 levels.Though a total of 22 cities have met the national ambient air quality standards (NAAQS) by reporting annual average PM10 concentrations of less than 60 micrograms per cubic metre (g/m3), Chennai is only big metro that met the acceptable limit by recording annual average concentration of 58 g/m3. On the other hand, the PM10 levels in Delhi, Kolkata, Mumbai, Hyderabad and Bengaluru continue to be higher than the acceptable limit. Exposure to PM10 leads to and exacerbates numerous health conditions, including asthma, cancer, stroke, and lung disease. A total of 64 cities have shown a reduction in PM10 levels by more than 20% in 2024-25 with respect to base year 2017-18 and 25 of these cities achieved a reduction of more than 40%.Among the cities that showed the most improvement, Bareilly reported a decline of 77% in PM10 levels (from 207 g/m3 to 48 g/m3), followed by a 74% dip in Varanasi (230 to 59 g/m3), 59% in Firozabad (247 to 100 g/m3), 57% in Dehradun (250 to 107 g/m3), 56% in Moradabad (222 to 96 g/m3) and 55% in Kanpur (227 to 102 g/m3). Besides Chennai, the other cities which reported acceptable PM10 levels in 2024-25 included Bareilly, Nellore, Silchar, Sivasagar, Rajamuhndry, Kadapa, Tuticorin and Trichy.