Smog, Microplastics, Thermal Pollution — UPSC Environment Notes

Three pollution stories dominate India's current environmental discourse: winter smog over Delhi and the Indo-Gangetic plains, the silent flood of microplastics into every ecosystem, and the thermal power plant pollution that still supplies over 70% of India's electricity. For UPSC, understanding these three is essential for both current affairs (prelims) and critical analysis (mains). This guide consolidates the science, the Indian policy response, and the exam angles in a single note.

Part 1: Smog — urban India's annual crisis

What is smog?

Smog ("smoke + fog") is a visible air pollution mixture. Two main types:

• London-type (sulphurous smog) — cold, humid; coal-burning + sulphur dioxide + water vapour. Historic London killer smog of 1952.
• Los Angeles-type (photochemical smog) — warm, sunny; vehicle emissions + NOx + VOCs + sunlight produce ground-level ozone. Characteristic of Delhi, Bangalore, Mexico City.

Delhi's winter smog is a complex photochemical + particulate hybrid with heavy PM2.5 loading from combustion, dust, and secondary aerosols.

Key pollutants

• Particulate Matter (PM2.5, PM10).
• Nitrogen oxides (NO, NO2).
• Sulphur dioxide (SO2).
• Volatile Organic Compounds (VOCs).
• Ozone (O3) — tropospheric, a secondary pollutant.

Mitigation devices used in India

Smog towers

• Large vertical air purifiers with 48 fans and HEPA H14 filters removing up to 99.99% of PM.
• Design capacity: 1.3 million cubic metres per hour of cleaned air.
• Installed at Connaught Place (Delhi) and Anand Vihar (2021) — largely pilot installations.
• Effectiveness at city scale has been questioned by IIT-B and US EPA studies.

Anti-smog guns

• Cannon-shaped devices spraying atomised water droplets to wash out particulates.
• Mounted on mobile tanker trucks.
• Deployed at construction sites (mandatory in Delhi for projects >20,000 sq m) and on major roads.

Structural remedies

• BS-VI fuel (April 2020).
• Public transport expansion (metro, e-buses).
• CNG/LPG-based private vehicles.
• Ethanol blending (E20 by 2025-26).
• Industrial emission monitoring.
• Stubble burning alternatives — Pusa decomposer, Happy Seeder.
• Dust control measures at construction sites.
• Banning pet coke and furnace oil.

UPSC quick facts

• GRAP — Graded Response Action Plan (4 stages) under CAQM.
• CAQM Act 2021 replaced the EPCA.
• NCAP target: 40% PM reduction by 2025-26.

Part 2: Microplastics — the invisible pollutant

What are microplastics?

Plastic fragments less than 5 mm in size. They are found in every ocean, every major river, and even human blood and placenta per recent biomedical studies.

Types

• Primary microplastics — manufactured at microscopic size: microbeads in cosmetics, microfibres from synthetic textiles, nurdles (industrial pellets), abrasion particles from tyres.
• Secondary microplastics — produced by degradation of larger plastic items (bottles, bags, nets, ropes) through UV exposure, mechanical action, and weathering.

Pathways into the environment

Impacts

• Ingestion across trophic levels — from zooplankton to whales; accumulation in seafood.
• Chemical contamination — microplastics adsorb POPs (persistent organic pollutants).
• Physical injury to marine life.
• Food-chain biomagnification — reaches humans through fish, salt, water, beer.
• Deep-sea impacts — found in Mariana Trench sediments.
• Human health — inflammation, endocrine disruption (still being characterised).

Regulatory response

• India ban on cosmetic microbeads — phased under BIS standards.
• Plastic Waste Management Rules, 2022 — EPR for producers; single-use plastic ban (July 2022) on 19 items.
• Global Plastics Treaty — UNEP-led negotiations (Busan INC-5, 2024); India supports life-cycle approach but opposes production caps.
• Swachh Bharat 2.0 — waste stream cleanup.

UPSC quick facts

• Microplastic size threshold: <5 mm.
• Nanoplastics: <100 nm.
• Primary vs secondary distinction is exam-critical.

Part 3: Thermal pollution and thermal power plants

What is thermal pollution?

Degradation of water quality by any process that changes ambient water temperature. Commonly caused by:

• Thermal power plants discharging cooling water.
• Industrial cooling (steel, cement, paper).
• Urban runoff from hot surfaces.
• Deforestation exposing streams to direct sunlight.

Thermal power plants in India

• Thermal (coal + gas + oil) accounts for ~54% of installed capacity and 70%+ of actual generation in 2024.
• India has over 210 GW of coal + lignite capacity, with plans to add ~80 GW by 2031-32.
• Air pollutants from TPPs: PM, SO2, NOx, mercury, fly ash.
• Water withdrawal and heating: cooling water discharge raises downstream river temperatures.
• Fly ash production is ~250 million tonnes/year; utilisation has improved but legacy ash ponds remain.

Factors affecting TPP location

Environmental impacts

• Air emissions — 40%+ of India's SO2, ~30% of NOx from TPPs.
• Thermal pollution of water — reduces dissolved oxygen, kills fish, triggers algal blooms.
• Fly ash impacts — leaching of heavy metals into groundwater.
• Land use — ash ponds displace communities, pollute soil.
• GHG emissions — ~40% of India's CO2 comes from power sector.

Regulatory regime

• Environment (Protection) Rules — emission limits for TPPs (revised 2015 for SO2, NOx, Hg, PM).
• Compliance deadline for FGD (Flue Gas Desulphurisation) — repeatedly extended; MoEFCC notified revised phase-wise timelines.
• Fly ash utilisation norms — CPCB and MoEFCC coordinate.
• Thermal discharge norms — effluents must be within 5°C of ambient river temperature.

The transition challenge

• India's Net Zero 2070 and 50% non-fossil installed capacity by 2030 pledges require a thermal transition.
• Just transition — Jharkhand, Odisha, Chhattisgarh coal economies need livelihood plans.
• Green Hydrogen Mission (2023) and renewables ramp-up provide alternatives.
• Carbon Capture, Utilisation, Storage (CCUS) — pilot projects in NTPC.

Integrated view: three pollutions, one narrative

Smog, microplastics, and thermal pollution share common drivers — combustion, consumption, and incomplete circular systems. Their solutions also share common architecture:

UPSC relevance

Prelims bullets

• Photochemical smog requires NOx + VOCs + sunlight.
• Microplastic <5 mm; nanoplastic <100 nm.
• FGD = Flue Gas Desulphurisation.
• Thermal effluent norm: 5°C above ambient.
• Smog towers use HEPA H14 filters.

Mains angles

• "Analyse the efficacy of smog towers and anti-smog guns in tackling Delhi's air pollution."
• "Discuss microplastics as an emerging pollutant and India's regulatory response."
• "Examine the environmental footprint of thermal power plants and strategies for a just energy transition."

Essay hooks

• Three pollutants, one consumption culture.
• India's pollution triangle — air, water, and the plastic in between.
• Just transition and the thermal legacy.

Latest developments (2024-26)

Updated context: verify with CPCB, MoEFCC, and UNEP releases.

• Global Plastics Treaty negotiations (INC-5 Busan, 2024) — no final agreement; talks continue 2025.
• FGD compliance extended by MoEFCC for TPPs until 2026-30 depending on category.
• CAQM winter 2024 measures — GRAP Stage IV invoked multiple times; smog tower future uncertain.
• Microplastic studies by NIOT and NCCR expanded to Indian coasts.
• COP29 methane pledges — cover landfill and oil-gas; indirect bearing on smog chemistry.

For UPSC the clean framing: India's pollution challenge is not one problem; it is an interconnected trio of air-smog, aquatic microplastics, and thermal plant legacy. Solutions must be integrated — circular economy, clean energy, and stricter enforcement — not symptomatic (smog towers alone).

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