Pollution: UPSC Previous Year Questions (Environment and Ecology)
39 previous year UPSC Prelims questions on pollution are listed here, from 2005 to 2025. UPSC asks about pollutants and their sources, WHO air quality guidelines, plastics in everyday items, mercury from coal, PFAS, copper smelting and methods to reduce air pollution. The explanations name the pollutant, its source and its effect.
Explanations state facts as of the year each question was asked; words like “recently” refer to that year.
Showing 11–20 of 39 questions
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UPSC 2021Environment and Ecology · Pollution
Q11. Why is there a concern about copper smelting plants? 1. They may release lethal quantities of carbon monoxide into the environment. 2. The copper slag can cause the leaching of some heavy metals into the environment. 3. They may release sulphur dioxide as a pollutant. Select the correct answer using the code given below.
Explanation
Copper Smelting is a process of applying heat to ore in order to extract a base metal. Smelting uses heat and a chemical reducing agent to decompose the ore, driving off other elements as gases or slag and leaving the metal base behind. It is the method of extracting pure elemental copper (Cu) from copper concentrate (CuFeS₂).
Statement 1 is incorrect: Copper smelting generally does not release lethal quantities of carbon monoxide (CO) into the environment.
Statement 2 and 3 are correct: Some smelting processes can also produce large quantities of solid waste, known as slag. This slag may leach heavy metals (arsenic, cadmium, lead or mercury depending on the composition of the ore) into groundwater reservoirs. Smelting processes are known to emit high quantities of air pollutants such as hydrogen fluoride, sulphur dioxide, oxides of nitrogen, offensive and noxious smoke fumes, vapours, gases, and other toxins.
Exam tip:
For S1, ’’Lethal quantities" is an extreme phrase, what is lethal quantity? How to define it? It’s all vague and hence more probable to be false, giving correct option B
UPSC 2021Environment and Ecology · Pollution
Q12. With reference to furnace oil, consider the following statements: 1. It is a product of oil refineries. 2. Some industries use it to generate power. 3. Its use causes sulphur emissions into the environment. Which of the statements given above are correct?
Explanation
Statement 1 is correct: Furnace oil or fuel oil is a dark viscous residual product of crude-oil distillation. It is used as a fuel in different types of combustion equipment.
Statement 2 is correct: Marine engines and slow speed engines use Furnace oil for power generation, they are used for drying tea leaves. Thermic fluid heaters and hot air generators also use Furnace oil.
Statement 3 is correct: The emissions of oxides of sulphur are a direct result of the sulphur content of the fuel oil.
Additional insight:
Furnace oil is a dark, viscous residual fuel obtained by blending mainly heavier components from crude distillation units. Compared to other petroleum products, it has a relatively low flash point and high viscosity. Its major advantages are:
High energy content, making it an efficient fuel choice for heating purposes Often cost-competitive compared to other heating options Readily available in many regions, ensuring a consistent supply Furnace/fuel oil combustion can produce emissions, including sulfur dioxide (SO₂), nitrogen oxides (NOx), and particulate matter
UPSC 2021Environment and Ecology · Pollution
Q13. Magnetite particles, suspected to cause neurodegenerative problems, are generated as environmental pollutants from which of the following? 1. Brakes of motor vehicles 2. Engines of motor vehicles 3. Microwave stoves within homes 4. Power plants 5. Telephone lines Select the correct answer using the code given below.
Explanation
Magnetite particles are a highly magnetic mineral form of iron and are known to be present in air pollution. Exposure to airborne particulate matter (PM) is associated with pulmonary, cardiovascular and neurological problems.
Option 1 is correct: Vehicle brake systems are the major source of airborne magnetite at the roadside.
Option 2 is correct: Petrol and diesel-engine exhaust are also a source of airborne magnetite.
Option 4 is correct: Other sources of Magnetite pollution include Power plants. Options 3 and 5 are incorrect: Household microwave stoves and telephone lines not are established as sources of airborne magnetite particles. Other sources of Magnetite pollution include microwave Stoves within homes, As per WHO, Telephone lines produce low frequency, low energy electromagnetic fields which are the potential source of magnetite particles.
Exam tip:
For S5, Had telephone lines been a real source of neurodegenerative magnetite particles, the effects would have surfaced in public health long ago -- given our lifelong proximity. Since no such pattern is observed, the claim lacks merit. Hence likely false. Giving option B as correct.
UPSC 2021Environment and Ecology · Pollution
Q14. The ‘Common Carbon Metric’, supported by UNEP, has been developed for
Explanation
The Common Carbon Metric’ is a protocol developed by United Nations Environment Program’s Sustainable Buildings & Climate Initiative (UNEP-SBCI) for measuring energy use & reporting GHG emissions from Building Operations. Its purpose is to support greenhouse gas (GHG) emission’s reductions through accurate measurement of energy efficiency improvements in building operations.
UPSC 2021Environment and Ecology · Pollution
Q15. What is blue carbon?
Explanation
Blue Carbon is the carbon captured by the world’s ocean and coastal ecosystems. There are three types of coastal ecosystems -- mangroves, seagrasses and tidal marshes; these store half the "blue" carbon buried beneath the ocean floor. These areas absorb and store carbon at a much faster rate than other areas, such as forests, and can continue to do so for millions of years. The carbon found in coastal soil is often thousands of years old.
UPSC 2020Environment and Ecology · Pollution
Q16. Which of the following are the reasons/factors for exposure to benzene pollution? 1. Automobile exhaust 2. Tobacco smoke 3. Wood burning 4. Using varnished wooden furniture 5. Using products made of polyurethane Select the correct answer using the code given below:
Explanation
At room temperature, benzene is a colorless or pale yellow liquid with a sweet odor and is highly flammable. It evaporates quickly into the air, and its vapor is denser than air, which can cause it to settle in low-lying areas. Benzene is a toxic air pollutant released from various sources and it can also contaminate water.
Option (a) is correct: Natural sources of benzene include volcanoes and forest fires. It is also present in gasoline, cigarette smoke, and crude oil, fuel evaporation, coal and oil combustion, and other activities. In various industries, benzene is used as a raw material to produce chemicals for making plastics, resins, nylon, and synthetic fibers. It is also found in the production of certain lubricants, rubbers, dyes, detergents, drugs, and pesticides. Although varnishes and paints may contain benzene, and the thermal breakdown of polyurethane can release benzene among other substances, these are not well-established as sources of benzene pollution.
UPSC 2020Environment and Ecology · Pollution
Q17. According to India’s National Policy on Biofuels, which of the following can be used as raw materials for the production of biofuels? 1. Cassava 2. Damaged wheat grains 3. Groundnut seeds 4. Horse gram 5. Rotten potatoes 6. Sugar beet Select the correct answer using the code given below:
Explanation
National Policy on Biofuels 2018 categorizes biofuels as "Basic Biofuels" viz. First Generation (1G) bioethanol & biodiesel and "Advanced Biofuels" - Second Generation (2G) ethanol, Municipal Solid Waste (MSW) to drop-in fuels, Third Generation (3G) biofuels, bio-CNG etc. to enable the extension of appropriate financial and fiscal incentives under each category. First-Generation Biofuels (also referred to as Basic biofuels) i.e. bioethanol and biodiesel, are produced from types of bio-mass that are often used for food, such as corn, soy, and sugarcane. These biofuels are made through fermentation or chemical processes that convert the oils, sugars, and starches in the bio-mass into liquid fuels. Second-Generation Biofuels (also referred to as Advanced bio-fuels) i.e, ethanol, municipal solid waste to drop-in fuels, are produced from non-food biomass, such as perennial grass and fast-growing trees. The processes to make them often involve converting fibrous non-edible material called "cellulose" into fuel. Third-generation biofuels are derived from algae and bacteria, which can produce large quantities of lipid oils or other biofuels like biomethanol or biohydrogen. Algae, in particular, grows quickly and has the potential to generate more biomass per unit of land compared to conventional crops.
Option (a) is correct: The Policy expands the scope of raw material for ethanol production by allowing the use of Sugarcane Juice, Sugar containing materials like Sugar Beet, Sweet Sorghum, Starch containing materials like Corn, Cassava, Damaged food grains like wheat, Broken rice, Rotten Potatoes.
UPSC 2020Environment and Ecology · Pollution
Q18. Which one of the following statements best describes the term ‘Social Cost of Carbon’? It is a measure, in monetary value, of the:
Explanation
Social Cost of Carbon is best described as the measure of monetary value of long-term damage done by a tonne of CO₂ emissions in a given year. The social cost of carbon (SCC) is used to estimate in dollars all economic damage that would result from emitting one ton of carbon dioxide into the atmosphere. India’s country-level social cost of carbon emission was estimated to be the highest at $86 per tonne of CO₂. It means the Indian economy will lose $86 by emitting each additional tonne of CO₂. India is followed by the US ($48) and Saudi Arabia ($47).
UPSC 2020Environment and Ecology · Pollution
Q19. Consider the following statements: 1. Coal ash contains arsenic, lead and mercury. 2. Coal-fired power plants release sulphur dioxide and oxides of nitrogen into the environment. 3. High ash content is observed in Indian coal. Which of the statements given above is/are correct?
Explanation
Statement 1 is correct: Coal ash contains contaminants like mercury, cadmium and arsenic. Without proper management, these contaminants can pollute waterways, groundwater, drinking water, and the air.
Statement 2 is correct: Burning of fossil fuels (which contain sulphur and nitrogenous matter) such as coal and oil in power stations and furnaces or petrol and diesel in motor engines produce sulphur dioxide and nitrogen oxides, which also leads to ‘acid rain’.
Statement 3 is correct: Indian Coal has comparatively higher ash content than imported coal due to the drift theory of the formation of coal deposits in India. Coal seams formed due to drift theory contain higher ash as compared to the in-situ theory of formation.
UPSC 2019Environment and Ecology · Pollution
Q20. In the context of which one of the following are the terms ‘pyrolysis and plasma gasification’ mentioned?
Explanation
Waste-to-Energy (WTE) technologies consist of any waste treatment process that creates energy in the form of electricity or heat from several types of waste: from the semi-sol-id (e.g. thickened sludge from effluent treatment plants) to liquid (e.g. domestic sewage) waste. Landfill gas recovery, Gasification, Pyrolisis, Thermal Depolymerisation are examples of Waste-to-Energy (WTE) technologies.
Option (d) is correct: Pyrolysis is a process of chemical de-composition of organic matter brought about by heat. In this process, the organic material is heated in the absence of air until the molecules thermally break down to become a gas comprising smaller molecules (known collectively as syngas). Gasification can also take place as a result of partial combustion of organic matter in the presence of a restricted quantity of oxygen or air. The gas, so produced, is known as producer gas. The gases produced by pyrolysis mainly comprise carbon monoxide (25%), hydrogen and hydrocarbons (15%), and carbon dioxide and nitrogen (60%). It is used commercially as a waste to energy system that converts municipal solid waste into synthesis gas (syngas) containing hydrogen and carbon monoxide that can be used to generate power.
Answer key for these questions
Q
UPSC year
Correct answer
11
2021
(b) 2 and 3 only
12
2021
(d) 1, 2 and 3
13
2021
(b) 1, 2 and 4 only
14
2021
(a) Assessing the carbon footprint of building operations around the world
15
2021
(a) Carbon captured by oceans and coastal ecosystems
16
2020
(a) 1, 2 and 3 only
17
2020
(a) 1, 2, 5 and 6 only
18
2020
(a) long-term damage done by a tonne of CO₂ emissions in a given year.
19
2020
(d) 1, 2 and 3
20
2019
(d) Waste-to-energy technologies
What UPSC has tested in Pollution
Cigarette butts, eyeglass lenses and car tyres all contain plastic.
Artificial rain to reduce air pollution uses silver iodide and potassium iodide.
Coal-based thermal power plants are a major source of mercury pollution.
PFAS are widespread in drinking water, food packaging and consumer products, and are not easily degraded.
Frequently asked questions
How many previous year UPSC questions are there on Pollution?
This page covers 39 previous year UPSC Prelims GS Paper-I questions on Pollution (Environment and Ecology), asked from 2005 to 2025. Each has the correct answer and an explanation.
Which common items contain plastic?
Cigarette butts, whose filters are made of cellulose acetate, a plastic; eyeglass lenses, which are often plastic polymers; and car tyres, which contain synthetic rubber and microplastic-shedding polymers.
What are PFAS?
Per- and polyfluoroalkyl substances, a large group of synthetic chemicals used in non-stick, waterproof and firefighting products. They are called forever chemicals because they resist breakdown and can build up in animal bodies.
Which chemicals are used in cloud seeding?
Silver iodide and potassium iodide, besides dry ice. They act as nuclei around which ice crystals form, helping clouds produce rain, and they are tried as a way of washing pollutants out of the air.
