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 31–39 of 39 questions
Browse by year
UPSC 2014Environment and Ecology · Pollution
Q31. There is some concern regarding the nanoparticles of some chemical elements that are used by the industry in the manufacture of various products. Why? 1. They can accumulate in the environment and contaminate water and soil. 2. They can enter the food chains. 3. They can trigger the production of free radicals. Select the correct answer using the code given below.
Explanation
Nanoparticles are used in the manufacture of scratch proof eyeglasses, crack-resistant paints, anti-graffiti coatings for walls, transparent sunscreens, stain-repellent fabrics, and self-cleaning windows, and ceramic coatings for solar cells. Additionally, stronger, lighter, cleaner, and more intelligent surfaces and systems can be created with nanoparticles.
Statement 1 is correct: A matter particle with dimension ranging from 1 to 100 nanometers is referred to as nanoparticle. Nanoparticles can accumulate in the environment and contaminate water and soil.
Statement 2 is correct: Nanoparticles can also enter the food chain and cross cell membranes.
Statement 3 is correct: Nanoparticles can trigger free radicals and may damage cells in organs like the liver, heart, or blood.
Additional insight:
Health Implications Of Nanoparticles:
Nanoparticles enhance drug delivery and target-specific treatment. However, some nanoparticles may reduce a drug’s efficacy or introduce toxicity risks to non-target orgAns:
Nanoparticles can accumulate in the liver and spleen, potentially altering liver function and triggering inflammatory responses. Certain nanoparticles can trigger immune responses, leading to inflammation or allergic reactions. Some act as allergens or induce antibody formation, affecting overall immune function. Negatively charged nanoparticles can penetrate the skin, increasing concerns over cosmetic and pharmaceutical applications. Ingested nanoparticles may accumulate in the gastrointestinal tract, impacting gut health and metabolism. Nanoparticles can induce oxidative stress, leading to cellular damage and potential links to cancer and neurodegenerative diseases. This can weaken the body’s antioxidant defences, causing long-term health risks.
UPSC 2014Environment and Ecology · Pollution
Q32. Brominated flame retardants are used in many household products like mattresses and upholstery. Why is there some concern about their use? 1. They are highly resistant to degradation in the environment. 2. They are able to accumulate in humans and animals. Select the correct answer using the code given below.
Explanation
Brominated Flame Retardants (BFRs) are mixtures of man-made chemicals that are added to a wide variety of products, including for industrial use, to make them less flammable. They are used commonly in plastics, textiles and electrical/electronic equipment. Statements 1 is correct: Brominated Flame Retardants (BFRs)don’t degrade easily in fact they are highly resistant to degradation in the environment. Statements 2 is correct: Some brominated flame retardants were identified as persistent, bioaccumulative, and toxic to both humans and the environment and were suspected of causing neurobehavioral effects and endocrine disruption.
UPSC 2013Environment and Ecology · Pollution
Q33. Which of the following can be found as pollutants in the drinking water in some parts of India? 1. Arsenic 2. Sorbitol 3. Fluoride 4. Formaldehyde 5. Uranium Select the correct answer using the codes given below.
Explanation
Water Pollution is the contamination of water bodies, usually as a result of human activities. Heavy metal water pollution is the contamination of water with toxic heavy metals, such as lead, mercury, cadmium, arsenic, and chromium etc. Heavy metals can enter the water through natural processes and human activities. Options 1, 3 and 5 are correct: Arsenic, Fluoride, Iron, Uranium, Nitrate, are some major groundwater pollutants in India.
Option 2 is incorrect: Sorbitol is a sugar alcohol found in fruits and plants with diuretic, laxative and cathartic properties. It is not related with drinking water pollution.
Option 4 is incorrect: Formaldehyde is used to preserve fish longer. The use of this chemical is banned in fresh foods by the Food Safety and Standards Authority of India. The International Agency for Research on Cancer (IARC) of WHO classifies formaldehyde as "carcinogenic to humans". Formaldehyde is not established as a drinking water pollutant.
Additional insight:
Water Quality Criteria according to CPCB Drinking Water Source without conventional treatment but after disinfection Total Coliforms Organism MPN/100ml shall be 50 or less pH between 6.5 and 8.5 Dissolved Oxygen 6mg/l or more Biochemical Oxygen Demand 5 days 20C 2mg/l or less Drinking water source after conventional treatment and disinfection Total Coliforms Organism MPN/100ml shall be 5000 or less pH between 6 to 9 Dissolved Oxygen 4mg/l or more Biochemical Oxygen Demand 5 days 20C 3mg/l or less
UPSC 2013Environment and Ecology · Pollution
Q34. Due to improper/indiscriminate disposal of hold and used computers or their parts, which of the following are released into the environment as e-waste? 1. Beryllium 2. Cadmium 3. Chromium 4. Heptachlor 5. Mercury 6. Lead 7. Plutonium Select the correct answer using the codes given below:
Explanation
E-waste is any electrical or electronic equipment that’s been discarded. Recently, India’s first e-waste clinic was inaugurated in Bhopal. E-waste Sources Constituents PCBs, glass panels, and Computer monitors Lead Resistors & Semiconductors Cadmium Relays and switches, &PCBs Mercury Galvanised steel plates & decorator or hardener Chromium Cabling, Computer & housing Plastics & PVC Electronic equipments & circuit boards Brominated flame-retardants Front panels of CRTs Barium, Phosphorus & Heavy metals Copper wires, PCB tracks Copper Nickel Cadmium batteries Nickel Lithium-ion battery Lithium Motherboards Beryllium Options 1, 2, 3, 5 and 6 are correct: All elements in these options are the harmful constituents that are released into the environment due to improper disposal of e-waste.
Option 4 is incorrect: Heptachlor is a pesticide classified under Persistent Organic Pollutants (POPs) per the Stockholm Convention. It is unrelated to e-waste.
Option 7 is incorrect: Plutonium, while used in some industrial and military applications, is a radioactive material and is not classified as part of e-waste.
UPSC 2013Environment and Ecology · Pollution
Q35. Acid rain is caused by the pollution of environment by
Explanation
Normal rain has a pH of about 5.6 when pH falls below this; it is called Acid rain (pH 4.2 to 4.4). Acid rain results when Sulphur Dioxide (SO₂) & Nitrogen Oxides (NOX) react with water, oxygen & other chemicals to form Sulfuric & Nitric acids. NOx + SO₂ + Moisture + other chemicals Acid Rain (HNO₃ + H₂ SO₄) Acid rain harms microorganisms in the soil; inhibits the activity of nitrogen fixation bacteria; soil acidification; ocean acidification; affects the growth of plants; food chain; kills aquatic animals; corrosion of metals and weathering of stone buildings & statues.
UPSC 2013Environment and Ecology · Pollution
Q36. Photochemical smog is a resultant of the reaction among
Explanation
Photochemical smog, often referred to as "Los Angeles smog," is most commonly found in urban areas with high numbers of automobiles. It does not require smoke or fog to form. This type of smog is formed from the nitrogen oxides and hydrocarbon (peroxyacetyl nitrate, a hazardous pollutant) vapors released by vehicles and other sources, which then undergo photochemical reactions in the lower atmosphere in the presence of sunlight.
UPSC 2013Environment and Ecology · Pollution
Q37. Improper handling and storage of cereal grains and oilseeds result in the production of toxins known as aflatoxins which are not generally destroyed by the normal cooking process. Aflatoxins are produced by:
Explanation
Aflatoxins are produced by certain species of fungi (moulds), specifically Aspergillus flavus and Aspergillus parasiticus, which often grow on stored grains and oilseeds under conditions of high humidity and temperature. Exposure to aflatoxins can lead to serious health issues, including liver cancer, especially in children. Beyond health risks, aflatoxins cause significant economic losses, with an estimated 25% of global food crops affected annually.
UPSC 2011Environment and Ecology · Pollution
Q38. There is a concern over the increase in harmful algal blooms in the seawaters of India. What could be the causative factors for this phenomenon? 1. Discharge of nutrients from the estuaries. 2. Run-off from the land during the monsoon. 3. Upwelling in the seas. Select the correct answer from the codes given below:
Explanation
A rapid rise in the population of algae in an aquatic system is known as an algal bloom, marine bloom, or water bloom. Algal blooms can appear in both marine and freshwater habitats. "Harmful algal blooms (HAB)" are blooms that can affect wildlife or the environment. Harmful Algal Bloom can lead to fish die-offs, cities cutting off water to residents, or states having to close fisheries.
Statement 1 is correct: Estuaries receive nutrient-rich water from rivers which can include agricultural runoff, sewage, and industrial effluents. These nutrients, particularly nitrogen and phosphorus promote the growth of algae causing algal blooms.
Statement 2 is correct: Heavy rainfall during the monsoon season can cause significant runoff from agricultural fields, urban areas, and other land surfaces. This runoff can carry fertilizers, pesticides, and other nutrients into the sea, providing the necessary conditions for algal blooms
Statement 3 is correct: Water that rises to the surface as a result of upwelling is typically colder and is rich in nutrients, which again leads to algal blooms.
UPSC 2005Environment and Ecology · Pollution
Q39. Consider the following statements: 1. Kyoto protocol came into force in the year 2005. 2. Kyoto protocol deals primarily with the depletion of the ozone layer. 3. Methane as a greenhouse gas is more harmful than carbon dioxide. Which of the statements given above is/are correct?
Explanation
The Kyoto Protocol is an international treaty that commits industrialized nations to reducing greenhouse gas emissions (the third Conference of the Parties) in 1997 in Kyoto, Japan.
Statement 1 is correct: The Kyoto Protocol officially came into force on February 16, 2005.
Statement 2 is incorrect: The Kyoto Protocol primarily focuses on reducing greenhouse gas emissions to combat climate change, not on the depletion of the ozone layer. The ozone layer issue is addressed by the Montreal Protocol, which focuses on phasing out substances that deplete the ozone layer.
Statement 3 is correct: Methane (CH₄) is a more potent green-house gas than carbon dioxide (CO₂) in the short term. Although CO₂ persists longer in the atmosphere, methane has a much higher global warming potential over a 20-year period--about 84 times more potent than CO₂.
Answer key for these questions
Q
UPSC year
Correct answer
31
2014
(d) 1, 2 and 3
32
2014
(c) Both 1 and 2
33
2013
(c) 1, 3 and 5 only
34
2013
(b) 1, 2, 3, 5 and 6 only
35
2013
(d) nitrous oxide and sulphur dioxide
36
2013
(a) NO₂, O₃ and peroxyacetyl nitrate in the presence of sunlight
37
2013
(c) moulds
38
2011
(d) 1, 2 and 3
39
2005
(b) 1 and 3
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.
