In the cities of our country, which among the following atmospheric gases are normally considered in calculating the value of Air Quality Index? Select the correct answer using the code given below.

Answer: (b) 2, 3 and 4 only

CO, NO₂ and SO₂ are AQI gases; CO₂ and methane are not.

Statement by statement

1. ✗ NO CO₂ is a greenhouse gas, not an AQI pollutant.

2. ✓ YES CO is one of the AQI pollutants.

3. ✓ YES NO₂ is one of them.

4. ✓ YES SO₂ is one of them.

5. ✗ NO Methane is not in the AQI.

The idea

The Air Quality Index is a health index. It counts only what harms a person who breathes the air today. Carbon dioxide and methane harm the climate over decades but do not make you ill at the levels found in city air, so they are left out.

Eight pollutants are measured → Each gets its own sub-index → The worst sub-index becomes the day’s AQI → Shown as one number, one colour, one description

The trap

Greenhouse gases feel like “air pollution”, but AQI is about health.

Also know

The eight: PM10, PM2.5, nitrogen dioxide, sulphur dioxide, carbon monoxide, ozone, ammonia and lead. Six bands: Good, Satisfactory, Moderate, Poor, Very Poor and Severe. India launched the national index in 2014. Delhi’s Graded Response Action Plan is triggered by these bands.