UPSC Prelims 2016 · Question 11 of 98

UPSC Prelims 2016 question on Air Quality Index Gases

In the cities of our country, which among the following atmospheric gases are normally considered in calculating the value of Air Quality Index?

1. Carbon dioxide
2. Carbon monoxide
3. Nitrogen dioxide
4. Sulfur dioxide
5. Methane

Select the correct answer using the code given below.

  1. 1, 2 and 3 only
  2. 2, 3 and 4 only
  3. 1, 4 and 5 only
  4. 1, 2, 3, 4 and 5
Show answer

Answer: B. 2, 3 and 4 only

Verdict

The answer is 2, 3 and 4 only. Carbon monoxide, nitrogen dioxide and sulphur dioxide are counted in the Air Quality Index; carbon dioxide and methane are not.

Analysis

The National Air Quality Index considers eight pollutants for which short term national ambient air quality standards are prescribed, namely PM10, PM2.5, nitrogen dioxide, sulphur dioxide, carbon monoxide, ozone, ammonia and lead. Statements 2, 3 and 4 are therefore CORRECT. Statements 1 and 5 are INCORRECT. Carbon dioxide and methane are greenhouse gases affecting the global climate but are not toxic at ambient concentrations, so they are not local air quality pollutants and do not enter the index.

Source

Press Information Bureau material on the National Air Quality Index and press commentary on urban air pollution.

How to crack it

This is a fundamental concept fused with a news hook, so keep the two categories of atmospheric problem strictly apart. Air quality is about substances harmful to human health at the point of exposure, while climate change is about gases that trap heat globally. Carbon dioxide and methane belong to the second list and never to the first. Sorting any gas into health hazard or heat trapper before answering resolves this entire question family.

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