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 ?
Show answer
Answer: B. Statement 1 is correct: WHO's 2021 guidelines set PM2.5 at 15 µg/m³ for 24 hours and 5 µg/m³ annual mean. Statement 2 is wrong: ozone peaks in sunny, hot weather, not bad weather. Statement 3 is wrong: it is PM2.5, not PM10, that can cross the lung barrier into blood. Statement 4 is correct: excess ozone can trigger asthma. So 1 and 4.
Watch for: Students mix up PM10 and PM2.5; only the finer particles reach the bloodstream.
Why the other options are wrong
- A. Wrong because PM10 does not enter the bloodstream; PM2.5 does.
- C. Wrong because statements 2 and 3 are incorrect.
- D. Wrong because ozone peaks in sunny weather, so statement 2 is incorrect.
Source to check: WHO Global Air Quality Guidelines, September 2021 (who.int)
Answer from the official UPSC key. Written and fact-checked by AI against the official key. Spotted a mistake? Report it.