Pollution: Chapter test

In March 2016 the Ministry and the CPCB revised the categorisation of industrial sectors on the basis of a pollution index score from 0 to 100: Red for a score of 60 and above, Orange for 41–59, Green for 21–40 and White for up to 20. The White category, covering 36 practically non-polluting sectors such as assembly of air coolers or bicycles, does not need consent to operate; intimation to the State Board is enough. Red category industries are generally not allowed in ecologically fragile areas and protected areas.

The SWM Rules, 2026 define four streams. Wet waste is kitchen and garden waste such as peels, food and flowers; dry waste is plastic, paper, metal, glass, wood and rubber for recycling; sanitary waste is used diapers, sanitary towels, tampons and condoms; and special care waste covers household items with hazardous content, such as paint cans, bulbs, mercury thermometers and medicines, which must go to authorised agencies or designated collection centres (PIB, 28 January 2026).

Phytoremediation uses plants to clean up pollution, and it has several forms. In phytoextraction, plants (often 'hyperaccumulators' such as Indian mustard for lead) absorb metals through their roots and move them to the harvestable shoots, which are cut and safely disposed of or processed. Phytostabilisation only locks pollutants in the root zone so that they do not spread. Rhizofiltration uses roots to absorb pollutants from water, and phytovolatilisation turns some pollutants, such as selenium or mercury, into gases released through the leaves.

Statements 1 and 2 are correct. The SWM Rules, 2026 were notified on 27 January 2026 under the Environment (Protection) Act, 1986, superseding the 2016 rules, and took effect on 1 April 2026 (PIB, 28 January and 30 March 2026). They make four-stream segregation mandatory: wet waste for composting or biomethanation, dry waste for material recovery facilities, sanitary waste wrapped and stored separately, and special care waste for authorised collection. Statement 3 is wrong: the rules apply to every urban and rural local body, as well as to SEZs, industrial townships, railways, airports, ports, defence establishments and all waste generators.

Statements 1 and 2 are correct. The amendment of 12 August 2021 raised the minimum thickness of carry bags of virgin or recycled plastic from 50 to 75 microns from 30 September 2021 and to 120 microns from 31 December 2022; thicker bags are more likely to be reused and collected. The same amendment fixed a minimum of 60 GSM for non-woven plastic carry bags. Statement 3 is wrong: the rules expressly say that the thickness provision does not apply to carry bags made of compostable or biodegradable plastic, which must instead meet the specified standards and labelling (IS/ISO 17088:2021 for compostable plastic).

The EPR Guidelines (added in February 2022 and amended in 2024) divide plastic packaging into categories with separate targets for collection, recycling and use of recycled content. Category I is rigid packaging; Category II is flexible packaging of one layer or several layers of different plastics, including carry bags, sheets and sachets; Category III is multilayered packaging with at least one plastic and at least one non-plastic layer, such as chips packets with a metallised or paper layer; Category IV is compostable plastic, and Category V (from 2024) is biodegradable plastic. Category III is the hardest to recycle, so its recycled-content targets are the lowest.

Statements 1 and 2 are correct. The amendment of 14 March 2024 rewrote the definition of biodegradable plastics: they are plastics other than compostable plastics that degrade biologically in a specific environment such as soil, landfill, sewage sludge, fresh water or marine water without leaving any microplastics or visible, distinguishable or toxic residue. It also requires makers of compostable or biodegradable carry bags and commodities to get a CPCB certificate before marketing or selling. Statement 3 is wrong: the same amendment created EPR Category V for packaging and commodities of biodegradable plastic (Category IV covers compostable plastic), so they are inside the EPR system.

Statements 1, 2 and 3 are correct. The new rules were notified on 2 April 2025 (G.S.R. 219(E)) under sections 6, 8 and 25 of the Environment (Protection) Act, 1986, superseding the C&D Waste Management Rules, 2016, and came into force on 1 April 2026. They bring in extended producer responsibility: producers must meet rising recycling targets (25% of the previous year's waste in 2025-26, rising thereafter), registered recyclers issue EPR certificates on an online portal, and environmental compensation applies for violations. Statement 4 is wrong: waste covered by the Atomic Energy Act, defence and strategic projects, and waste from natural disasters or war are expressly excluded.

Silver iodide and potassium iodide are used (a). Cloud seeding sprays particles into suitable clouds so that water droplets or ice crystals form around them. Silver iodide is the standard agent, as its crystal shape is close to ice, and potassium iodide is used with it. Rain then washes dust and smoke out of the air. Options (b), (c) and (d) are wrong: silver nitrate, potassium nitrate and potassium chloride are not the usual agents, though common salt is used in some warm-cloud seeding.

Notice the catch: seeding needs clouds with enough moisture; it cannot make rain from a clear sky. Delhi tried cloud seeding against smog with IIT Kanpur in 2025, with little success because the air was too dry.

Answer as per the official UPSC answer key.

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Both statements are correct and II explains I (a). Statement I is right: discarded chewing gum is a major source of litter and pollution: spat-out gum sticks to streets and pavements for years, and is costly to clean. Statement II is right and explains it: most modern gum bases are synthetic polymers such as polyvinyl acetate and polyisobutylene, which are plastics, in place of the old natural chicle from the sapodilla tree. These do not break down, so gum stays in the environment.

Notice that Singapore has banned the sale of most chewing gum since 1992. Gum also adds to microplastics, and studies have found that chewing it can release microplastic particles into saliva. Some makers are going back to natural, biodegradable gum bases.

Answer as per the official UPSC answer key.

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Two statements are correct (b). Statement 1 is right: small-scale gold mining, which uses mercury to bind gold particles, is the largest source of mercury released by people worldwide. Statement 2 is right: coal burning, mainly in thermal power plants, comes next, as coal holds traces of mercury. Statement 3 is wrong under UPSC's key: "no known safe level" is what the WHO says about lead. For mercury, health agencies set tolerable intake limits, though they treat it as highly toxic.

Notice the Minamata Convention (2013, in force 2017), named after Japan's mercury poisoning disaster from factory waste. India has ratified it. Mercury turns into methylmercury in water and builds up in fish, harming the brain.

Answer as per the official UPSC answer key.

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Statements 1 and 4 are correct (b). Statement 1 is right: the 2021 WHO Air Quality Guidelines set PM2.5 at 15 µg/m³ for the 24-hour mean and 5 µg/m³ for the annual mean. Statement 2 is wrong: ground-level ozone forms when sunlight acts on pollutants, so it peaks in hot, sunny weather, not in bad weather. Statement 3 is wrong: PM2.5, not PM10, is fine enough to pass the lung barrier into the bloodstream. Statement 4 is right: excess ozone irritates airways and can trigger asthma.

Notice that India's National Ambient Air Quality Standards (2009) are much looser: PM2.5 at 60 (24-hour) and 40 (annual). The National Clean Air Programme (2019) targets cuts in 131 cities.

Answer as per the official UPSC answer key.

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Factors 1, 2 and 3 are correct in UPSC's key (a). Benzene is released when carbon-rich material burns incompletely. Major sources are vehicle exhaust (1), as benzene is in petrol and is formed during burning; tobacco smoke (2), the main source for smokers; and wood burning (3), including stoves and forest fires. Benzene is a known cause of leukaemia and other blood cancers. UPSC's key leaves out varnished furniture (4) and polyurethane products (5), which give off other volatile organic compounds such as formaldehyde.

Notice India's limits: BS-VI fuel (from 2020) limits benzene in petrol to 1%, and the National Ambient Air Quality Standards set a yearly limit of 5 µg/m³. Petrol pumps use vapour recovery systems.

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Only statement 2 is correct (b). Statement 1 is wrong because both bodies are statutory. The CPCB was set up in 1974 under the Water (Prevention and Control of Pollution) Act and was later given powers under the Air Act, 1981 and the Environment Protection Act. The NGT was set up under the NGT Act, 2010. Statement 2 is right because the NGT gives fast environmental justice, deciding cases within six months, and reduces the load on higher courts. The CPCB works to keep streams and wells clean and to improve air quality.

The NGT's principal bench is in New Delhi, with four zonal benches. Notice the principles it applies: sustainable development, the precautionary principle, and polluter pays, under Section 20 of the NGT Act.

Answer as per the official UPSC answer key.

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