JAGTIV · Previous Year Questions

UPSC

ENVIRONMENT · 2015

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Previous Year Question

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. Sulphur dioxide

  5. Methane

Select the correct answer using the code given below:

A.

1, 2 and 3 only

B.

2, 3 and 4 only

C.

1, 4 and 5 only

D.

1, 2, 3, 4 and 5

Correct Answer: B

Detailed Solution

  • The National Air Quality Index (NAQI) expresses the concentrations of different air pollutants through a simple numerical value and health-based category.

  • India’s National Air Quality Index was launched in 2014.

  • The Indian AQI covers eight pollutants—PM₁₀, PM₂.₅, nitrogen dioxide, sulphur dioxide, carbon monoxide, ozone, ammonia and lead.

  • Carbon monoxide is included in the AQI. It is produced mainly through the incomplete combustion of fuels, and vehicular emissions are one of its major sources in urban areas.

  • Carbon monoxide can bind with haemoglobin in the blood and reduce the oxygen-carrying capacity of the body.

  • Nitrogen dioxide is included in the AQI. It is emitted by vehicles, thermal power plants and other high-temperature combustion processes.

  • Nitrogen dioxide can affect the respiratory system and contributes to the formation of tropospheric ozone and secondary particulate matter.

  • Sulphur dioxide is included in the AQI. It is produced mainly by the combustion of sulphur-containing coal and oil.

  • Sulphur dioxide can cause respiratory problems and contributes to the formation of sulphate particles and acidic deposition in the atmosphere.

  • Carbon dioxide is not included in the Indian AQI. It is a major greenhouse gas but is not measured as a health-based local pollutant under the general outdoor-air AQI.

  • Methane is also not included in the Indian AQI. It is a powerful greenhouse gas and a precursor of tropospheric ozone, but it is not among the eight designated AQI pollutants.

  • A separate sub-index is calculated from the concentration of each included pollutant. The overall AQI is generally determined by the pollutant having the highest sub-index.

  • The AQI is classified into categories such as Good, Satisfactory, Moderately Polluted, Poor, Very Poor and Severe.

  • Therefore, carbon monoxide, nitrogen dioxide and sulphur dioxide from the given list are included in the calculation of the AQI.

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