UPSC Previous Year Question | Prelims GS | 2022

In the context of WHO Air Quality Guidelines, consider the following statements: 1. PM2.5's 24-hour mean should not exceed 15 ug/m3 and PM2.5's annual mean should not exceed 5 ug/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 blood-stream. 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

Answer

Correct Answer

1 and 4 only

Explanation

Statement 1 is correct (WHO 2021 guidelines: 24-hr PM2.5 ≤15 µg/m3, annual ≤5 µg/m3). Statement 4 is correct — excess ozone triggers asthma. Statement 2 is incorrect — ozone pollution peaks during sunny, not inclement, weather. Statement 3 is incorrect — it is PM2.5, not PM10, that penetrates the lung barrier into the bloodstream.

Topics: air pollution, environment, pm2.5 and ozone, who air quality guidelines