Kolkata and adjoining metropolitan areas including Howrah, Hooghly, North 24 Parganas, South 24 Parganas and Nadia have far fewer vehicles and industries compared to the national capital region (NCR).

Air quality index is used by government agencies to communicate to the public how polluted the air is. Public health risks increase as the AQI rises. Eight pollutants namely particulate matter PM10, ...