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UPSC Prelims 2022 Paper-1 📅 05 Jun, 2022

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 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?

A
(a) 1, 3 and 4
B
(b) 1 and 4 only
C
(c) 2, 3 and 4
D
(d) 1 and 2 only
Result Summary
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UPSC Prelims
2022 • 05 Jun, 2022 • Paper-1
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 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?
Correct Answer
(b) 1 and 4 only
Guideline Limits: Statement 1 is correct. According to the updated 2021 WHO Air Quality Guidelines, the safe limits for PM2.5 are strictly set at 5 µg/m³ for ......
Ref/Book : UPSC Prelims 2022
Ref. Subject Environment
Chapter -
Ref. Topic Pollution
Pg. No -
💡 Analysis & Explanation
Guideline Limits ▼
Statement 1 is correct. According to the updated 2021 WHO Air Quality Guidelines, the safe limits for PM2.5 are strictly set at 5 µg/m³ for the annual mean and 15 µg/m³ for the 24-hour mean.
Pollutant Behavior ▼
Statement 2 is incorrect. Ground-level ozone is formed through photochemical reactions requiring intense sunlight and heat, meaning highest levels occur during sunny, warm days, not inclement (bad) weather. Statement 3 is incorrect. PM10 is inhalable into the respiratory tract, but it is the much finer PM2.5 (and smaller) particles that can deeply penetrate the lung barrier and enter the bloodstream.
Health Impact ▼
Statement 4 is correct. High concentrations of ozone are known respiratory irritants that can significantly trigger and worsen asthma attacks.
Conclusion ▼
Statements 1 and 4 represent scientifically accurate information.
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