Question map
In the context of WHO Air Quality Guidelines, consider the following statements: 1. The 24-hour mean of PMā.ā should not exceed 15 Āµg/mĀ³ and annual mean of PMā.ā should not exceed 5 Āµg/mĀ³. 2. In a year, the highest levels of ozone pollution occur during the periods of inclement weather. 3. PMāā 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?
Explanation
The correct answer is Option 2 (1 and 4 only). This is based on the 2021 WHO Air Quality Guidelines and fundamental atmospheric chemistry.
- Statement 1 is correct: The WHO updated its Global Air Quality Guidelines in 2021, lowering the recommended limits. The annual mean for PMā.ā is now 5 Āµg/mĀ³ and the 24-hour mean is 15 Āµg/mĀ³.
- Statement 2 is incorrect: Surface-level ozone is a photochemical pollutant formed by the reaction of precursors (NOx and VOCs) in the presence of sunlight. Therefore, ozone levels peak during sunny, hot, and stagnant weather, not during "inclement" (stormy or rainy) weather.
- Statement 3 is incorrect: While PMāā can settle deep in the lungs, it is generally too large to cross the blood-air barrier. It is PMā.ā (fine particulate matter) that is capable of penetrating the lung barrier and entering the bloodstream.
- Statement 4 is correct: High concentrations of ozone are potent respiratory irritants. They can cause airway inflammation, reduce lung function, and are well-documented triggers for asthma attacks.
PROVENANCE & STUDY PATTERN
Guest previewThis is a 'Hybrid Trap': it combines a hard data memorization check (Statement 1: WHO 2021 Update) with standard static concepts (Statement 2 & 4: Ozone formation/Health). It punishes aspirants who read news headlines ('WHO updates guidelines') but failed to memorize the specific summary table.
This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.
- Statement 1: According to the WHO Air Quality Guidelines, what are the recommended 24āhour mean and annual mean concentration limits for PM2.5 (Āµg/mĀ³)?
- Statement 2: According to WHO sources, do the highest annual groundālevel ozone pollution levels typically occur during periods of inclement weather?
- Statement 3: According to WHO or WHOācited medical literature, can PM10 particles penetrate the lung barrier and enter the bloodstream?
- Statement 4: According to WHO or leading health authorities, can elevated ambient ozone concentrations trigger or exacerbate asthma symptoms?
- This is the WHO summary table of recommended 2021 AQG levels showing both annual and 24āhour values for PM2.5.
- It lists the AQG (most stringent) levels: 5 Āµg/mĀ³ (annual) and 15 Āµg/mĀ³ (24āhour).
- This World Bank document cites the WHO targets and repeats the recommended AQG values.
- It explicitly states the annual PM2.5 target is 5 Āµg/mĀ³ and the 24āhour target is 15 Āµg/mĀ³.
States that the National Air Quality Index considers PM2.5 and refers to averaging periods 'up to 24-hourly averaging period', highlighting that PM2.5 guidelines are specified for 24āhour means.
A student could use this to focus on WHO guideline values expressed for 24āhour averages and compare national AQI categories to WHO 24āhour limits.
Describes India's National Air Quality Monitoring Programme (NAMP) and its role in ascertaining compliance with National Ambient Air Quality Standards (NAAQS), implying the practice of comparing measured PM2.5 to defined annual and shortāterm standards.
A student could look up WHO AQG numerical annual and 24āhour PM2.5 values to compare against national NAAQS and NAMP monitoring results.
Gives numeric particulate emissions for BSāVI engines (20ā40 Āµg/m3), providing a real-world magnitude for PM concentrations used in regulatory contexts.
A student could use these magnitudes as a baseline to judge whether WHO guideline values (annual/24āhour) are more or less stringent than typical regulatory/technical emission-related concentrations.
Provides an example of an air quality standard (8āhour ozone = 100 Āµg/m3), showing that healthābased guidelines are often stated as specific Āµg/m3 limits for defined averaging times.
A student could infer that WHO similarly states PM2.5 limits as numeric Āµg/m3 values tied to averaging periods (annual and 24āhour) and seek those specific numbers for direct comparison.
Lists particulate matter (TSP, RPM) as major pollutants, underlining that particulate fractions like PM2.5 are standard categories monitored and regulated.
A student could use this to justify searching for standard guideline values specifically for PM2.5 (as a recognized pollutant fraction) expressed for annual and 24āhour means.
This statement analysis shows book citations, web sources and indirect clues. The first statement (S1) is open for preview.
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This statement analysis shows book citations, web sources and indirect clues. The first statement (S1) is open for preview.
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This statement analysis shows book citations, web sources and indirect clues. The first statement (S1) is open for preview.
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