According to Central Pollution Control Board, the Air Quality category for IND-AQI range of 101 – 200 is

Correct — option (3), Moderate.

India's National Air Quality Index has six categories, each tied to a range of index values. An AQI of 101–200 is the third band, which CPCB's note "About National Air Quality Index" and the 2014 launch release name "Moderately polluted"; the option's "Moderate" names the same band.

The full scale runs: Good (0–50), Satisfactory (51–100), Moderately polluted (101–200), Poor (201–300), Very Poor (301–400) and Severe (401–500).

For the 101–200 band, the stated likely health impact is breathing discomfort to people with lung disease such as asthma, and discomfort to people with heart disease, children and older adults.

The idea to remember: the first two bands span 50 points each; from 101 upward each band spans 100 — Moderately polluted, Poor, Very Poor, Severe.

Why the others are wrong

• (1)
  Good — Good is the category for an AQI of 0–50, where the likely health impact is minimal. An index of 101–200 lies two bands higher.

  For PM2.5, the Good band corresponds to a 24-hour average concentration of 0–30 µg/m³.

• (2)
  Satisfactory — Satisfactory is the category for an AQI of 51–100, the band just below the one in the stem. Its stated impact is possible minor breathing discomfort to sensitive people.

  For PM2.5 it corresponds to a 24-hour average of 31–60 µg/m³. Once the AQI goes above 100, the category becomes Moderately polluted.

• (4)
  Poor — Poor is the category for an AQI of 201–300, the band just above the one in the stem. It may cause breathing discomfort to people on prolonged exposure, and discomfort to people with heart disease.

  For PM2.5 it corresponds to a 24-hour average of 91–120 µg/m³.

An air quality index turns measurements of several pollutants into one number, one category name and one colour. At its launch, the Environment Minister described India's index as "One Number- One Colour-One Description".

The National AQI covers eight pollutants: PM10, PM2.5, NO2, SO2, CO, O3, NH3 and Pb (lead). For each, a sub-index is calculated from its measured concentration against health-based breakpoints.

The worst sub-index sets the overall AQI. A location's AQI therefore reflects its most serious pollutant, not an average of all eight.

Key facts

• Environment Minister Prakash Javadekar launched the National Air Quality Index in New Delhi on 17 October 2014.
• The six AQI categories are Good, Satisfactory, Moderately polluted, Poor, Very Poor and Severe.
• The index covers eight pollutants: PM10, PM2.5, NO2, SO2, CO, O3, NH3 and Pb.
• The worst sub-index among the pollutants determines the overall AQI.
• Breakpoints use 24-hour averages for PM10, PM2.5, NO2, SO2, NH3 and Pb, and 8-hour values for CO and O3.

Common traps

• The two lowest bands span 50 points each (0–50, 51–100); from 101 upward each band spans 100 points. Do not assume equal bands throughout.
• CPCB's note "About National Air Quality Index" names the 101–200 band "Moderately polluted". An option reading "Moderate" refers to the same band, so do not reject it for the shorter name.
• The overall AQI is the worst sub-index, not an average. One pollutant in the Poor range makes the AQI Poor even if every other pollutant is in the Good range.

UnlockIAS will link similar questions from RAS Pre 2013 here once that paper is published on this site.

• practice — not a real PYQ

  Under India's National Air Quality Index, the overall AQI of a location is determined by

  • (a)the average of the sub-indices of all eight pollutants
  • (b)the worst (highest) sub-index among the pollutants
  • (c)the sub-index of PM2.5 alone
  • (d)the sum of the sub-indices of PM10 and PM2.5
  Answer(2) — The worst sub-index determines the overall AQI. Option (1) is wrong because the sub-indices are not averaged; options (3) and (4) are wrong because no single pollutant or pair of pollutants is fixed as the basis.
• practice — not a real PYQ

  According to India's National Air Quality Index, an AQI value of 350 falls in which category?

  • (a)Poor
  • (b)Very Poor
  • (c)Severe
  • (d)Moderately polluted
  Answer(2) — Very Poor covers 301–400. Option (1), Poor, covers 201–300; option (3), Severe, covers 401–500; option (4), Moderately polluted, covers 101–200.