Pollution: UPSC Previous Year Questions (Environment and Ecology)
3 previous year UPSC Prelims questions on Pollution (Environment and Ecology). Choose an option to see the answer and explanation.
Explanations state facts as of the year each question was asked; words like “recently” refer to that year.
Showing 1–3 of 3 questions
UPSC 2025Environment and Ecology · Pollution
Q1. Consider the following: 1. Cigarette butts 2. Eyeglass lenses 3. Car tyres How many of them contain plastic?
Explanation
Plastics are synthetic polymers widely used in modern products due to their versatility, durability, and cost-effectiveness. Cigarette Butts: Cigarette butts, made of cellulose acetate, are the most littered plastic waste worldwide, with 4.5 trillion butts discarded annually--66% of the 6 trillion cigarettes smoked. Each releases about 15,000 microplastic fibers, leaching nicotine, arsenic, and lead, and takes up to 10 years to degrade. Eyeglass Lenses: Eyeglass lenses are now mostly plastic-- CR-39, polycarbonate (used in 90% of glasses), Trivex, and high-index plastics--preferred for being lightweight, shatter-resistant, and optically clear. Improper disposal contributes to plastic waste, but recycling remains limited. Car Tyres: Car tyres contain 24% synthetic rubber, 19% natural rubber, carbon black, and synthetic fibers like nylon and polyester. Tyre wear particles (TWPs) contribute 10-28% of oceanic microplastics, totaling 1.2-2.8 million tonnes annually. Hence, option (c) is correct.
Additional insight:
Microplastics, fragments of plastic less than 5 mm, originate from primary sources (e.g., microbeads in cosmetics) or secondary sources (e.g., breakdown of larger plastics like synthetic fabrics or tyres). They are a global pollution threat, found in oceans, air, soil, food, and even human organs, contributing to environmental and health concerns.
Exam tip:
You can try, The "NOT" approach for all statements, this tests the improbability of negating a statement--if denying its impact seems highly unlikely, the statement is plausibly true. For example: Saying "Cigarette butts, Eyeglass lenses or car tyres do not contain plastic" seems highly implausible, suggesting that all three do contain plastic.
UPSC 2025Environment and Ecology · Pollution
Q2. Consider the following statements: Statement I: Activated carbon is a good and an attractive tool to remove pollutants from effluent streams and to remediate contaminants from various industries. Statement II: Activated carbon exhibits a large surface area and a strong potential for adsorbing heavy metals. Statement III: Activated carbon can be easily synthesized from environmental wastes with high carbon content. Which one of the following is correct in respect of the above statements?
Explanation
Statement I is correct: Activated carbon is an effective, versatile adsorbent for removing pollutants from effluent streams like wastewater and industrial discharges, widely used in textile, pharmaceutical, and petrochemical industries. It removes organic compounds (e.g., phenols, dyes), heavy metals (e.g., lead, mercury), and VOCs with 90-99% efficiency. The EPA classifies it as a Best Available Technology (BAT) for wastewater treatment.
Statement II is correct: Its large surface area (500-1500 m²/g) and microporous structure (<2 nm pores) offer abundant adsorption sites. Surface functional groups (e.g., hydroxyl, carboxyl) enhance binding of cadmium, chromium, lead, and mercury, with 95-99% removal efficiency. High BET surface area and pore volume (0.5-2 cm²/g) explain its adsorption efficiency, reinforcing Statement I.
Statement III is correct: Activated carbon can be synthesized from environmental wastes (e.g., coconut shells, rice husks, bagasse, fruit peels, sewage sludge) via pyrolysis (400-800°C) and chemical/physical activation. Coconut shells yield >1000 m²/g, bagasse 800-1200 m²/g. This cost-effective, sustainable process supports its use in pollutant removal and aligns with circular economy goals
UPSC 2025Environment and Ecology · Pollution
Q3. Artificial way of causing rainfall to reduce air pollution makes use of
Explanation
Cloud-seeding is a technique used to modify weather by releasing silver iodide (AgI) into the atmosphere to facilitate the formation of ice crystals, enhancing the cloud’s ability to generate rain. In the process of cloud-seeding, chemicals like silver iodide, potassium iodide, and dry ice are dispersed into the sky via airplanes and helicopters.
Additional insight:
Cloud seeding is divided into two main types:
Hygroscopic Cloud Seeding: This approach promotes the growth of water droplets in liquid clouds by introducing salt particles, typically at the cloud’s base, which helps the droplets combine and become heavy enough to fall as rain. Glaciogenic Cloud Seeding: This method encourages the formation of ice crystals in supercooled clouds by releasing substances such as silver iodide or dry ice, which serve as ice nuclei, initiating ice formation and ultimately leading to precipitation.
Answer key for these questions
Q
UPSC year
Correct answer
1
2025
(c) All the three
2
2025
(a) Both Statement II and Statement III are correct and both of them explain Statement I
3
2025
(a) silver iodide and potassium iodide
Frequently asked questions
How many previous year UPSC questions are there on Pollution?
This page covers 3 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.
How should I use previous year UPSC questions for Prelims?
Attempt each question first, then open the answer and read the explanation for every option. Repeat by chapter, and track which statements UPSC reuses across years. Previous year questions show the exam pattern and difficulty level.
Which years are covered for Pollution?
Questions on Pollution (Environment and Ecology) are available for 14 years, from 2005 to 2025. Use the Year filter to practise a single paper.
