Soon before the passing of the Air Pollution Control Act, 1981 in India, an institute called NEERI had conducted a survey of the prevailing air quality in 9 major cities of India. Which of the following cities had SO₂ concentration exceeding the maximum tolerable value of 80 μg/m³?
- AAhmedabad
- BKolkataCorrect
- CNew Delhi
- DHyderabad
Solution
Concept
Before the Air Act 1981, NEERI's ambient air survey found high SO₂ in cities that burned a lot of coal.
Step-by-step solution
1. NEERI checked ambient air quality in 9 major Indian cities before the Air (Prevention and Control of Pollution) Act, 1981. 2. The main SO₂ sources at that time were burning coal in thermal power plants, industries and homes. 3. Kolkata (Calcutta) had heavy coal-based industry and domestic coal burning. 4. So Kolkata is the most likely city with SO₂ above the tolerable value of 80 μg/m³. 5. Answer: (B) Kolkata.
Explanation
SO₂ comes mainly from burning sulphur-containing coal. Kolkata used a lot of coal in industries, power plants and homes. So it is the city most likely to have crossed the 80 μg/m³ limit for SO₂.
Why the other options are wrong
Ahmedabad, New Delhi and Hyderabad are believed to have had SO₂ values below the 80 μg/m³ limit in that survey; their main problem was suspended particulate matter.
Shortcut
Old Indian SO₂ problem = coal city = Kolkata.
Common mistake
Choosing New Delhi, whose main problem in this survey was suspended particulate matter, not SO₂.
Correct answer: B) Kolkata