UPSC Prelims 2022 · Question 44 of 98

UPSC Prelims 2022 question on WHO Air Quality Guidelines

In the context of WHO Air Quality Guidelines, consider the following statements:

1. The 24-hour mean of PM 2.5 should not exceed 15 µg/m3 and annual mean of PM2.5 should not exceed 5 µg/m3.

2. In a year, the highest levels of ozone pollution occur during the periods of inclement weather.

3. PM10 can penetrate the lung barrier and enter the bloodstream.

4. Excessive ozone in the air can trigger asthma.

Which of the statements given above are correct?

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

Answer: B. 1 and 4 only

Verdict

Correct statements: 1 and 4 → Option (b).

Statement by statement

Statement 1 – CORRECT: According to WHO guidelines, the annual average for PM2.5 should not exceed 5 micrograms per cubic metre of air, while the 24-hour average should not exceed 15 micrograms per cubic metre.

Statement 2 – INCORRECT: Ozone at ground level is one of the major constituents of photochemical smog. It is formed by the reaction with sunlight (photochemical reaction) of pollutants such as nitrogen oxides (NOx) from vehicle and industry emissions and VOCs. As a result, the highest levels of ozone pollution occur during periods of SUNNY weather — not inclement weather.

Statement 3 – INCORRECT: While particles with a diameter of 10 microns or less (PM10) can penetrate and lodge deep inside the lungs, the even more health-damaging particles are those with a diameter of 2.5 microns or less (PM2.5). PM2.5 — not PM10 — can penetrate the lung barrier and enter the blood system.

Statement 4 – CORRECT: Excessive ozone in the air can have a marked effect on human health. It can cause breathing problems, trigger asthma, reduce lung function and cause lung diseases.

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