Indore might be the cleanest city of India for the sixth time in a row this year since 2017 but it has flunked big time on the air quality front. Recent analysis of 132 cities by the environment ministry shows that Indore is among the 37 cities whose PM10 (respirable particulate matter) pollutant levels actually increased in 2021-22 over 2017.Indore might be the cleanest city of India for the sixth time in a row this year since 2017 but it has flunked big time on the air quality front. Recent analysis of 132 cities by the environment ministry shows that Indore is among the 37 cities whose PM10 (respirable particulate matter) pollutant levels actually increased in 2021-22 over 2017.