UPSC CSE Prelims
Environmental Pollution Previous Year Questions (PYQs)
Showing solved Previous Year Questions for Chapter: Environmental Pollution
Topic Breakdown: Scroll →
In the cities of our country, which among the following atmospheric gases are normally considered in calculating the value of Air Quality Index?
- Carbon dioxide
- Carbon monoxide
- Nitrogen dioxide
- Sulphur Dioxide
- Methane
Select the correct answer using the code given below
Detailed Explanation:
Answer: Option 2 — 2, 3 and 4 Only
❌ Statement 1 – Incorrect: Carbon dioxide (CO₂) is a greenhouse gas but is NOT included in India's National Air Quality Index (AQI) calculation, which focuses on pollutants with direct health impacts rather than climate change gases.
✅ Statement 2 – Correct: Carbon monoxide (CO) is one of the eight pollutants monitored under the National AQI; it is a toxic gas from incomplete combustion that reduces oxygen transport in blood.
✅ Statement 3 – Correct: Nitrogen dioxide (NO₂) is included in the AQI calculation as a major pollutant from vehicle exhausts and industrial processes that causes respiratory problems.
✅ Statement 4 – Correct: Sulphur dioxide (SO₂) is a criteria pollutant for the AQI, released from burning fossil fuels in power plants and industries.
❌ Statement 5 – Incorrect: Methane (CH₄) is a potent greenhouse gas but is NOT directly measured in the National AQI calculation.
Note: India's National AQI monitors eight pollutants: PM₁₀, PM₂.₅, NO₂, SO₂, CO, O₃, NH₃, and Pb.
Which of the following are the key features of ‘National Ganga River Basin Authority (NGRBA)’?
- The river basin is the unit of planning and management.
- It spearheads the river conservation efforts at the national level.
- One of the Chief Ministers of the State through which the Ganga flows becomes the Chairman of NGRBA on a rotation basis.
Select the correct answer using the code given below.
Detailed Explanation:
Answer: Option 1 — 1 and 2 only
✅ Statement 1 – Correct: NGRBA adopts the river basin as the unit of planning and management, moving away from fragmented state-wise approaches to a holistic basin-level conservation strategy.
✅ Statement 2 – Correct: NGRBA was established to spearhead river conservation efforts at the national level for the Ganga. It functions as the apex planning, financing, monitoring, and coordinating authority for Ganga rejuvenation.
❌ Statement 3 – Incorrect: The Prime Minister of India serves as the Chairman of NGRBA, not Chief Ministers on rotation. Chief Ministers of Ganga basin states are members of the Authority along with relevant Union Cabinet Ministers.
What can be the impact of excessive/inappropriate use of nitrogenous fertilizers in agriculture?
- The proliferation of nitrogen-fixing microorganisms in the soil can occur.
- Increase in the acidity of soil can take place
- Leaching of nitrate to the ground-water can occur.
Select the correct answer using the code given below.
Detailed Explanation:
❌ Statement 1 – Incorrect: Excessive nitrogenous fertilizers suppress nitrogen-fixing microorganisms because abundant soil nitrogen reduces their competitive advantage and metabolic activity.
✅ Statement 2 – Correct: Nitrogenous fertilizers (especially ammonium-based) undergo nitrification, releasing H⁺ ions that increase soil acidity.
✅ Statement 3 – Correct: Excess nitrates (NO₃⁻) are highly water-soluble and leach into groundwater, causing nitrate contamination and eutrophication of water bodies.
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With reference to ‘fly ash’ produced by the power plants using coal as fuel, which of the following statements is/are correct?
- Fly ash can be used in the production of bricks for building construction.
- Fly ash can be used as a replacement for some of the Portland cement content of concrete.
- Fly ash is made up of silicon dioxide and calcium oxide only and does not contain any toxic elements.
Select the correct answer using the code given below
Detailed Explanation:
✅ Statement 1 – Correct: Fly ash possesses pozzolanic properties that enhance the strength and durability of bricks used in construction.
✅ Statement 2 – Correct: Fly ash can replace 20-30% of Portland cement in concrete, improving workability, reducing heat of hydration, and increasing long-term strength.
❌ Statement 3 – Incorrect: While fly ash mainly contains SiO2, Al2O3, and CaO, it also contains trace amounts of heavy metals like arsenic, mercury, chromium, and lead.
Which of the following are some important pollutants released by the steel industry in India?
- Oxides of sulphur
- Oxides of nitrogen
- Carbon monoxide
- Carbon dioxide
Select the correct answer using the code given below.
Detailed Explanation:
✅ Statement 1 – Correct: Steel industry uses coal and coke containing sulphur; combustion and sintering processes release oxides of sulphur (SOx).
✅ Statement 2 – Correct: High-temperature operations in blast furnaces cause atmospheric nitrogen to react with oxygen, forming oxides of nitrogen (NOx).
✅ Statement 3 – Correct: Carbon monoxide (CO) is generated during reduction of iron ore and through incomplete combustion of carbon-based fuels.
✅ Statement 4 – Correct: Carbon dioxide (CO2) is released from chemical reduction of iron ore (coke reacting with ore) and combustion of fossil fuels.
There is some concern regarding the nanoparticles of some chemical elements that are used by the industry in the manufacture of various products. Why?
- They can accumulate in the environment, and contaminate water and soil.
- They can enter food chains.
- They can trigger the production of free radicals.
Select the correct answer using the code given below.
Detailed Explanation:
✅ Statement 1 – Correct: Nanoparticles are extremely small (1-100 nm) and resistant to degradation, allowing them to persist and accumulate in soil and water bodies, contaminating the environment.
✅ Statement 2 – Correct: Due to their microscopic size, nanoparticles can be absorbed by plants and microorganisms, entering the food chain and undergoing biomagnification at higher trophic levels.
✅ Statement 3 – Correct: Certain nanoparticles can induce oxidative stress in cells by triggering the production of reactive oxygen species (ROS) or free radicals, which damage DNA, proteins, and cell membranes, potentially causing inflammation and cancer.
Brominated flame retardants are used in many household products like mattresses and upholstery. Why is there some concern about their use?
- They are highly resistant to degradation in the environment.
- They are able to accumulate in humans and animals.
Select the correct answer using the code given below.
Detailed Explanation:
✅ Statement 1 – Correct: Brominated flame retardants (BFRs) are persistent organic pollutants (POPs) that are highly resistant to environmental degradation, remaining in ecosystems for extended periods.
✅ Statement 2 – Correct: BFRs are lipophilic (fat-soluble) and undergo bioaccumulation in fatty tissues of humans and animals, leading to potential endocrine disruption and neurotoxicity.
Due to improper/indiscriminate disposal of old and used computers or their parts, which of the following are released into the environment as e-waste?
- Beryllium
- Cadmium
- Chromium
- Heptachlor
- Mercury
- Lead
- Plutonium
Select the correct answer using the codes given below.
Detailed Explanation:
E-waste from computers contains heavy metals used in electronic components: Beryllium (motherboards, connectors), Cadmium (rechargeable batteries, circuit boards), Chromium (corrosion protection in steel plates), Mercury (fluorescent lamps, switches), and Lead (solder, CRT monitors).
Heptachlor is an organochlorine insecticide, not used in electronics, and Plutonium is a radioactive element found only in nuclear applications, not in computers.
Acid rain is caused by the pollution of the environment by -
Detailed Explanation:
Acid rain is caused by sulphur dioxide (SO₂) and nitrogen oxides (NOₓ) released from burning fossil fuels and vehicle emissions.
These gases react with water vapor, oxygen, and other atmospheric chemicals to form sulphuric acid (H₂SO₄) and nitric acid (HNO₃), which fall as acid rain.
Photochemical smog is a resultant of the reaction among -
Detailed Explanation:
Photochemical smog is formed when nitrogen dioxide (NO₂), volatile organic compounds (VOCs), and oxygen react in the presence of sunlight to produce ozone (O₃) and peroxyacetyl nitrate (PAN).
Option 1 correctly identifies the resultant components (NO₂, O₃, and PAN) that characterize photochemical smog, which forms through photochemical reactions triggered by ultraviolet (UV) sunlight.
Which of the following can be found as pollutants in the drinking water in some parts of India?
- Arsenic
- Sorbitol
- Fluoride
- Formaldehyde
- Uranium
Select the correct answer using the codes given below.
Detailed Explanation:
✅ Arsenic (1) – Correct: Found in groundwater of West Bengal, Bihar, Uttar Pradesh, Assam, Jharkhand due to natural leaching from arsenic-bearing rocks; causes arsenicosis and skin lesions.
❌ Sorbitol (2) – Incorrect: A sugar alcohol used as artificial sweetener and humectant; not a naturally occurring groundwater pollutant in India.
✅ Fluoride (3) – Correct: Endemic in Rajasthan, Andhra Pradesh, Tamil Nadu, Gujarat, Haryana and other states; causes dental and skeletal fluorosis from geological sources.
❌ Formaldehyde (4) – Incorrect: An industrial chemical and disinfectant; not a common groundwater contaminant in Indian drinking water systems.
✅ Uranium (5) – Correct: Detected in groundwater of Punjab, Rajasthan, Haryana and parts of southern India; leaches from uranium-bearing granitic rocks.
Lead, ingested or inhaled is a health hazard. After the addition of lead to petrol has been banned, what still are the sources of lead poisoning?
- Smelting units
- Pens and pencils
- Paints
- Hair oils and cosmetics
Detailed Explanation:
✅ Statement 1 – Correct: Smelting units release lead particles into air and soil during ore processing, making them a major source of environmental lead contamination.
❌ Statement 2 – Incorrect: Pencils contain graphite (carbon) and clay, not lead; the term "lead" is a historical misnomer.
✅ Statement 3 – Correct: Lead-based paints remain a significant hazard as deteriorating paint releases lead dust and chips that can be inhaled or ingested.
❌ Statement 4 – Incorrect: While some traditional cosmetics (surma/kohl) may contain lead, standard hair oils and modern cosmetics are not primary sources of lead poisoning.
The acidification of oceans is increasing. Why is this phenomenon a cause of concern?
- The growth and survival of calcareous phytoplankton will be adversely affected.
- The growth and survival of coral reefs will be adversely affected.
- The survival of some animals that have phytoplanktonic larvae will be adversely affected.
- The cloud seeding and formation of clouds will be adversely affected.
Detailed Explanation:
✅ Statement 1 – Correct: Calcareous phytoplankton (like coccolithophores) need carbonate ions to build calcium carbonate shells; ocean acidification reduces these ions, impairing their calcification, growth, and survival.
✅ Statement 2 – Correct: Coral reefs are made of calcium carbonate; increased acidity lowers the saturation state, making it harder for corals to build skeletons and can cause reef dissolution.
✅ Statement 3 – Correct: Many marine invertebrates (mollusks, echinoderms) have phytoplanktonic larvae sensitive to seawater chemistry changes; acidification impairs their development and shell formation, increasing mortality.
❌ Statement 4 – Incorrect: While acidification may reduce dimethyl sulfide (DMS) production affecting cloud condensation nuclei, this is an indirect climatic feedback, not a primary direct concern for ocean ecosystems.