WHO के वायु गुणवत्ता दिशानिर्देशों के सन्दर्भ में, निम्नलिखित कथनों पर विचार कीजिए :
- 1.PM2·5 का 24-घंटा माध्य 15 µg/m³ से अधिक नहीं बढ़ना चाहिए और PM2·5 का वार्षिक माध्य 5 µg/m³ से अधिक नहीं बढ़ना चाहिए ।
- 2.किसी वर्ष में, ओज़ोन प्रदूषण के उच्चतम स्तर प्रतिकूल मौसम के दौरान होते हैं ।
- 3.PM10 फेफड़े के अवरोध का वेधन कर रक्त-प्रवाह में प्रवेश कर सकता है ।
- 4.वायु में अत्यधिक ओज़ोन दमा को उत्पन्न कर सकती है ।
उपर्युक्त कथनों में कौन-से सही हैं ?
Read this question in English
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?
(a) 1, 3 and 4 · (b) 1 and 4 only · (c) 2, 3 and 4 · (d) 1 and 2 only
उत्तर और व्याख्या · explanation in English
Answer: (b) केवल 1 और 4
Statements 1 and 4 are correct. WHO's 2021 guidelines set PM2.5 at 5 µg/m3 a year and 15 µg/m3 over 24 hours, and ozone can trigger asthma. Ozone peaks in hot, sunny weather, not bad weather, and it is PM2.5, not PM10, that WHO says can enter the bloodstream.
- ✓ 1. The WHO Air Quality Guidelines (2021) recommend an annual average of 5 µg/m3 and a 24-hour average of 15 µg/m3 for PM2.5.
- ✗ 2. Ground-level ozone forms when pollutants react in sunlight, so it is most likely to reach unhealthy levels on hot sunny days, not in inclement weather.
- ✗ 3. Both PM2.5 and PM10 can go deep into the lungs, but WHO says only the finer PM2.5 can even enter the bloodstream.
- ✓ 4. Ozone irritates and inflames the airways, aggravates asthma and increases the frequency of asthma attacks.
Remember · WHO 2021: PM2.5 annual 5, 24-hour 15 µg/m3 (PM10: 15 and 45). Ozone peaks on hot sunny days and worsens asthma. Only PM2.5 reaches the blood.
Sources
- WHO, Billions of people still breathe unhealthy air: new WHO data, 4 April 2022 (Internet Archive copy) ↗ “The latest WHO Air Quality Guidelines (2021) recommend the following concentration limits for these pollutants: For PM 2.5 : Annual average 5 µg/m 3 ; 24-hour average 15 µg/m 3”
- WHO, WHO global air quality guidelines: questions and answers (Internet Archive copy) ↗ “PM₂.₅ and PM₁₀ are capable of penetrating deep into the lungs and PM₂.₅ can even enter the bloodstream, primarily resulting in cardiovascular and respiratory impacts.”
- US EPA, Ground-level Ozone Basics (Internet Archive copy) ↗ “Ozone is most likely to reach unhealthy levels on hot sunny days in urban environments, but can still reach high levels during colder months.”
- US EPA, Health Effects of Ozone Pollution (Internet Archive copy) ↗ “Aggravate lung diseases such as asthma, emphysema, and chronic bronchitis. Increase the frequency of asthma attacks.”
Question and answer: UPSC's official GS Paper I (2022, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·