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?
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A hard Environment multiple-choice question from UPSC Prelims 2022. Attempt it above, then check the correct answer and detailed explanation below.
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Correct answer: B. 1 and 4 only
Statement 1 matches the 2021 WHO guideline values (24-hour PM2.5 ≤ 15 µg/m³, annual ≤ 5 µg/m³) and statement 4 is correct — ozone can trigger asthma. Statement 2 is wrong — ozone peaks in hot, sunny (not inclement) weather. Statement 3 is wrong — it is the finer PM2.5, not PM10, that penetrates into the bloodstream. So 1 and 4 only — option (b).
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