Air pollution

Prelims and Mains

The standards name the pollutants that must be measured in ambient air and the level each of them may reach. The Air Quality Index reduces that day's readings to a single number, and the National Green Tribunal has now asked for three more pollutants to be brought into the measuring.

• The National Ambient Air Quality Standards cover twelve pollutants, and the Air Quality Index combines eight of them, particulate matter (PM10 and PM2.5), NO₂, SO₂, CO, O₃, NH₃ and lead, taking whichever is worst.
• Carbon dioxide and methane are not among them, so the index says nothing about the greenhouse gases.
• It runs in six bands, from Good, 0 to 50, to Severe, 401 to 500.
• Ambient air is sampled manually over 24 hours and read continuously at Continuous Ambient Air Quality Monitoring Stations (CAAQMS).
• The annual PM10 standard is 60 micrograms per cubic metre, four times the World Health Organization (WHO) guideline of 15.
• The Central Pollution Control Board (CPCB) is statutory under the Water Act, 1974, and the Commission for Air Quality Management (CAQM) under its own Act of 2021.
• The National Green Tribunal gave the CPCB ten weeks to standardise testing for three further ambient air pollutants, aluminium, iron and silica.