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UPSC PYQPrelims 2022

Civil Services Examination · Question 44

In the context of WHO Air Quality Guidelines, consider the following statements: 1. The 24-hour mean of PM2.5 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 & explanation

Answer: (B) 1 and 4 only

Explanation

The 2021 WHO limits for PM2.5 are 15 (24-h) and 5 (annual) µg/m³, and ozone triggers asthma. Ozone peaks in sunny, not inclement, weather, and it is PM2.5 (not PM10) that enters the bloodstream.