Standards and effects of pollutants under WHO guidelines
Question
In the context of WHO Air Quality Guidelines, consider the following statements: Which of the statements given above are correct?
- 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.
Options
1, 3 and 4
1 and 4 only
2, 3 and 4
1 and 2 only
Explanation
Statements 1 and 4 are correct; the 2021 WHO update aggressively tightened PM2.5 limits (5 µg/m³ annual), and ground-level ozone is a well-known respiratory irritant that triggers asthma. Statement 2 is incorrect; tropospheric ozone requires intense sunlight and heat to form, peaking during clear, sunny, heatwave conditions, not inclement weather. Statement 3 is incorrect; PM10 lodges in the upper respiratory tract; it is the much finer PM2.5 that deeply penetrates the lung barrier into the bloodstream.
Answer: (b).
Question details
Year
2022
Paper
GS Paper 1
Question
Q44
Subject
Environment
Sub-topic
Pollution & Waste
Type
Statement-based
Difficulty
Hard
Nature
Current-affairs-linked
Source hint
WHO Global Air Quality Guidelines 2021 Update
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