An Air Quality Index value in the range 201 to 300 falls in which category?
- A.Moderate
- B.Poor
- C.Very Poor
- D.Severe
Correct answer
Explanation
The correct answer is B, Poor. The National Air Quality Index has six bands: 0 to 50 is Good, 51 to 100 Satisfactory, 101 to 200 Moderate, 201 to 300 Poor, 301 to 400 Very Poor and 401 to 500 Severe. A sub-index is computed for each pollutant for which enough data are available, and the worst of these sub-indices becomes the AQI of the day, the pollutant responsible being named as the prominent pollutant. Option A is wrong because Moderate covers 101 to 200. Option C is wrong because Very Poor begins only at 301. Option D is wrong because Severe is the topmost band, from 401 to 500, at which even healthy people are affected and emergency restrictions are usually imposed. The index is published for eight pollutants, so it is worth memorising the bands as three pairs: fifty and a hundred, two hundred and three hundred, four hundred and five hundred.
Read the full article: Air Pollution and Air Quality: Pollutants, AQI and Laws
Practice Questions
View allWhich of the following is a secondary air pollutant?
- A.Sulphur dioxide
- B.Carbon monoxide
- C.Peroxyacetyl nitrate
- D.Particulate matter
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A secondary pollutant is never emitted from a source; it is manufactured in the atmosphere itself when primary pollutants react with one another or with sunlight.
Read the full explanation →Which of the following is the chief component of photochemical smog?
- A.Sulphur dioxide
- B.Ozone
- C.Methane
- D.Carbon dioxide
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Photochemical smog, also called Los Angeles smog, forms in warm, dry, sunny weather when oxides of nitrogen from vehicle exhaust and unburnt hydrocarbons react under ultraviolet light.
Read the full explanation →Carbon monoxide is dangerous to human beings mainly because it:
- A.Combines with haemoglobin to form carboxyhaemoglobin
- B.Dissolves in water to form a strong acid
- C.Destroys the ozone layer of the stratosphere
- D.Settles in the alveoli as fine dust
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Carbon monoxide binds to the haemoglobin of the blood roughly two hundred times more readily than oxygen does, and the carboxyhaemoglobin so formed cannot carry oxygen.
Read the full explanation →Along with the oxides of nitrogen, which gas is chiefly responsible for acid rain?
- A.Carbon monoxide
- B.Methane
- C.Sulphur dioxide
- D.Argon
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Sulphur dioxide, released when coal and oil containing sulphur are burnt, is oxidised in the atmosphere to sulphur trioxide, which dissolves in water droplets to give sulphuric acid.
Read the full explanation →The damage to the marble of the Taj Mahal, popularly called 'marble cancer', is caused chiefly by:
- A.Carbon dioxide
- B.Sulphur dioxide
- C.Chlorofluorocarbons
- D.Ground-level ozone
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Sulphur dioxide from industry and traffic around Agra is oxidised in the air and comes down as sulphuric acid, which attacks the calcium carbonate of marble.
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