In the context of WHO Air Quality Guidelines, consider the following statements:
- The 24-hour mean of PM2.5 should not exceed 15 ug/m³ and annual mean of PM2.5 should not exceed 5 ug/m³.
- In a year, the highest levels of ozone pollution occur during the periods of inclement weather.
- PM10 can penetrate the lung barrier and enter the bloodstream.
- Excessive ozone in the air can trigger asthma.
Which of the statements given above are correct?
Detailed Explanation:
Answer: Option 2 — 1 and 4 only
The WHO Air Quality Guidelines (2021) set stringent limits for particulate matter and other pollutants to protect public health. Statement 1 correctly states WHO's recommended limits for PM2.5, and Statement 4 correctly identifies ozone's role in triggering asthma. However, statements 2 and 3 contain factual errors regarding ozone formation conditions and the penetration capabilities of different particulate matter sizes.
✅ Statement 1 – Correct: WHO guidelines (2021) recommend 24-hour mean of PM2.5 should not exceed 15 µg/m³ and annual mean should not exceed 5 µg/m³.
❌ Statement 2 – Incorrect: Ozone pollution peaks during sunny, hot, and stagnant weather conditions, not during inclement weather; sunlight drives the photochemical reactions that produce ground-level ozone.
❌ Statement 3 – Incorrect: PM2.5 (not PM10) can penetrate the lung barrier and enter the bloodstream; PM10 particles are too large and typically deposit in the upper airways and bronchi.
✅ Statement 4 – Correct: Excessive ozone in the air irritates the respiratory system, triggers asthma attacks, and exacerbates other respiratory conditions.
📝 Short Notes: Air Pollutants and Health Effects
| Pollutant | Size/Characteristics | Health Impact | Formation Conditions |
|---|---|---|---|
| PM10 | Particles ≤10 µm | Deposits in upper airways; causes respiratory irritation, bronchitis | Dust, construction, combustion |
| PM2.5 | Particles ≤2.5 µm (fine) | Penetrates deep into lungs and enters bloodstream; affects heart, brain, organs | Combustion, vehicular emissions, industrial processes |
| Ground-level Ozone (O₃) | Secondary pollutant | Triggers asthma, reduces lung function, respiratory inflammation | Formed by photochemical reactions in sunlight (NOx + VOCs) |
- WHO Air Quality Guidelines (2021): PM2.5 annual mean: 5 µg/m³; 24-hour mean: 15 µg/m³
- WHO Air Quality Guidelines (2021): PM10 annual mean: 15 µg/m³; 24-hour mean: 45 µg/m³
- Ozone peaks: During summer months with high temperature, strong sunlight, and stagnant air masses
- Ultrafine particles (PM0.1): Even smaller than PM2.5, can directly enter blood and organs
- India's National Ambient Air Quality Standards (NAAQS): Less stringent than WHO guidelines; PM2.5 annual: 40 µg/m³, 24-hour: 60 µg/m³
Question 4 of 14 Air Pollution
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