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
Correct answer
Explanation
The correct answer is B, 1 and 4 only. The 2021 WHO guidelines set PM2.5 at 15 µg/m³ for a 24-hour mean and 5 µg/m³ for the annual mean, and ground-level ozone is a known trigger of asthma attacks.
WHO revised its Air Quality Guidelines in September 2021, the first update since 2005, and made them much stricter: the annual PM2.5 value fell from 10 to 5 µg/m³. Ground-level ozone is not emitted directly; it forms when nitrogen oxides and volatile organic compounds react in strong sunlight, so it irritates the airways and worsens asthma.
Statement 2 is wrong because ozone peaks in hot, sunny, still weather, not during inclement (cloudy, rainy) periods. Statement 3 is wrong because it is the finer PM2.5 that can cross the lung barrier into the blood; PM10 mostly stays in the nose, throat and upper lungs. So A and C (which include 3) and D (which includes 2) are wrong.
Exam tip: WHO 2021 PM2.5 = 15 (24-hour) and 5 (annual) µg/m³; ozone forms in sunlight.
Practice Questions
View allHow is permaculture farming different from conventional chemical farming?
1. Permaculture farming discourages monocultural practices but in conventional chemical farming, monoculture practices are predominant.
2. Conventional chemical farming can cause increase in soil salinity but the occurrence of such phenomenon is not observed in permaculture farming.
3. Conventional chemical farming is easily possible in semi-arid regions but permaculture farming is not so easily possible in such regions.
4. Practice of mulching is very important in permaculture farming but not necessarily so in conventional chemical farming.
Select the correct answer using the code given below.
- A.1 and 3
- B.1, 2 and 4
- C.4 only
- D.2 and 3
Show answer
Permaculture avoids monoculture, does not build up salt in the soil and relies on mulching; only statement 3 is wrong.
Read the full explanation →With reference to "Gucchi" sometimes mentioned in the news, consider the following statements:
1. It is a fungus.
2. It grows in some Himalayan forest areas.
3. It is commercially cultivated in the Himalayan foothills of north-eastern India.
Which of the statements given above is/are correct?
- A.1 only
- B.3 only
- C.1 and 2
- D.2 and 3
Show answer
Gucchi is the morel mushroom, a fungus that grows wild in Himalayan forests, but it is not commercially cultivated. Gucchi (Morchella esculenta) has a honeycomb-like cap and is one of the costliest mushrooms in the world, often selling for tens of thousands of rupees a kilogram.
Read the full explanation →With reference to the role of biofilters in Recirculating Aquaculture System, consider the following statements :
1. Biofilters provide waste treatment by removing uneaten fish feed.
2. Biofilters convert ammonia present in fish waste to nitrate.
3. Biofilters increase phosphorus as nutrient for fish in water.
How many of the statements given above are correct?
- A.Only one
- B.Only two
- C.All three
- D.None
Show answer
Only statement 2 is correct: the biofilter's job in a Recirculating Aquaculture System is to turn toxic ammonia into much less harmful nitrate.
Read the full explanation →What is 'Climate Neutral Now' initiative?
1. It encourages organizations and other interested stakeholders to act now in order to achieve a carbon neutral world by 2030.
2. It derives its aims from the Paris Agreement.
Select the correct answer using the code given below :
- A.1 only
- B.2 only
- C.Both 1 and 2
- D.Neither 1 nor 2
Show answer
Climate Neutral Now takes its aim from the Paris Agreement, but the target it works towards is a climate-neutral world by the middle of the century, not by 2030.
Read the full explanation →Which of the following statements is/are correct about 'Action for Climate Empowerment' (ACE)?
1. It is a term adopted by the UN Framework Convention on Climate Change.
2. This term is related to the Paris Agreement.
Select the correct answer using the code given below:
- A.1 only
- B.2 only
- C.Both 1 and 2
- D.Neither 1 nor 2
Show answer
Action for Climate Empowerment is the UNFCCC's own name for its work on climate education and public awareness, and it covers the Paris Agreement too.
Read the full explanation →