Indore slips to second in clean air survey; Mayor promises intensified anti-pollution measures to improve air quality. The local administration has blamed PM10 particles — dangerous airborne particles — for vehicle-heavy Indore’s slide from first place to second in the 2026 Clean Air Survey and has. New Delhi, May 4 (PTI) Indians have voted Indore in Madhya Pradesh as the cleanest city in the country, while Gonda in Uttar Pradesh has been.