Environment Studies

Unit 5 at a Glance

This unit studies pollution — how human activity damages air, water, soil and the human soundscape — and how we control it. The exam pattern for this unit is predictable: one question defines pollution and classifies pollutants; one question each goes to air, water, soil and noise pollution (causes → effects → control); solid waste management is a favourite long question; and the Bhopal gas tragedy (1984) is the most-asked case study.

1. What is Pollution? Types of Pollutants

A pollutant is the substance (or form of energy, like heat or noise) that causes pollution. Pollutants are classified in three useful ways:

(a) By origin — Primary vs Secondary

• Primary pollutants are emitted directly from a source: carbon monoxide (CO) from vehicles, sulphur dioxide (SO₂) from power plants, particulate matter from chimneys.
• Secondary pollutants form in the atmosphere by reactions between primary pollutants: ground-level ozone (O₃) and photochemical smog (PAN — peroxyacetyl nitrate) form when NO_x and hydrocarbons react in sunlight.

(b) By persistence — Biodegradable vs Non-biodegradable

• Biodegradable pollutants are broken down by microbes: sewage, food waste, paper.
• Non-biodegradable pollutants persist for years: plastics, DDT, heavy metals (mercury, lead), glass. These accumulate in food chains — biomagnification.

(c) By nature — Quantitative vs Qualitative

• Quantitative pollutants occur naturally but become harmful above a threshold concentration: CO₂, nitrogen oxides.
• Qualitative pollutants do not occur naturally at all: DDT, CFCs, plastics.

2. Air Pollution — Causes and Major Pollutants

Causes / Sources

• Natural: volcanic eruptions, forest fires, dust storms, pollen.
• Anthropogenic (man-made): vehicles (CO, NO_x, hydrocarbons, lead), thermal power plants and industries (SO₂, SPM, fly ash), burning of fossil fuels and crop residue (stubble burning in Punjab–Haryana every October–November worsens Delhi's smog), construction dust, indoor sources (chulhas, smoking).

Major air pollutants

3. Air Pollution — Effects, Control and the Air Act 1981

Effects

• Human health: asthma, bronchitis, lung cancer, eye irritation, reduced lung function in children.
• Acid rain: SO₂ and NO_x dissolve in rainwater forming sulphuric and nitric acids (rain pH below 5.6). Damages buildings — the classic Indian example is the yellowing of the Taj Mahal from Mathura refinery emissions.
• Photochemical smog: brownish haze over cities; reduces visibility, damages crops.
• Global effects: excess CO₂ drives global warming; CFCs deplete ozone.

Control measures

The Air (Prevention and Control of Pollution) Act, 1981

• Enacted in 1981 (amended in 1987 to include noise as an air pollutant).
• Establishes Central and State Pollution Control Boards (CPCB/SPCBs) with powers to set emission standards, declare air-pollution control areas, and prosecute violators.
• India's National Air Quality Index (AQI) (launched 2014) tracks 8 pollutants including PM10, PM2.5, NO₂, SO₂, CO, O₃.

4. Water Pollution — Sources, BOD, COD, Eutrophication

Sources

• Point sources — discharge at one identifiable spot: factory pipes, sewage outfalls.
• Non-point sources — diffused: farm runoff (fertilisers, pesticides), urban stormwater, oil spills from ships.
• Major pollutants: sewage (pathogens), industrial effluents (heavy metals — mercury, lead, cadmium; dyes from textile units), agricultural runoff (nitrates, phosphates, pesticides), oil spills, thermal discharge.

Key measurement terms (very important for exams)

Eutrophication and biomagnification

• Eutrophication: excess nitrates/phosphates (from fertilisers, sewage) trigger algal blooms. When algae die, decomposition consumes oxygen → DO crashes → fish die. The lake "ages" prematurely.
• Biomagnification: non-biodegradable toxins (DDT, mercury) concentrate at each step of the food chain — plankton → small fish → big fish → humans/birds. Classic case: DDT thinned eggshells of birds.

Water-borne diseases

Cholera, typhoid, dysentery, jaundice (hepatitis) spread through contaminated water. Arsenic in groundwater (West Bengal, Bihar) causes skin lesions and cancer; fluoride excess (Rajasthan) causes fluorosis of teeth and bones.

5. Water Pollution — Control, Water Act 1974, Ganga Action Plan

Control measures

• Sewage treatment plants (STPs): primary (settling), secondary (biological — activated sludge, trickling filters), tertiary (disinfection) treatment before discharge.
• Effluent Treatment Plants (ETPs) in industries; Common ETPs for industrial clusters.
• Reduce at source: low-phosphate detergents, organic farming, oil-spill containment booms.
• Rainwater harvesting and groundwater recharge to dilute and restore aquifers.

The Water (Prevention and Control of Pollution) Act, 1974

• India's first major environmental law, enacted in 1974 (amended 1988).
• Created the Central and State Pollution Control Boards; requires industries to take "consent to operate" and meet effluent standards.

Ganga Action Plan and Namami Gange

• Ganga Action Plan (GAP), 1986 — launched to clean the Ganga; only partially successful.
• Namami Gange — approved in 2014 as an integrated flagship programme (₹20,000 crore outlay) for abatement of pollution and rejuvenation of the Ganga.

6. Soil (Land) Pollution

Causes

• Agrochemicals: excessive fertilisers (nitrates) and pesticides/insecticides (DDT, BHC, endosulfan — endosulfan caused serious health damage in Kasaragod, Kerala).
• Industrial waste: heavy metals, fly ash, effluents dumped on land.
• Solid waste: plastics, e-waste, biomedical waste dumped in open.
• Mining: overburden dumps, acid mine drainage.
• Salinisation: waterlogging from over-irrigation (canal commands) makes soil saline and barren.

Effects and control

• Effects: loss of fertility, biomagnification of pesticides into food, groundwater contamination, loss of soil microbes.
• Control: judicious use of fertilisers/pesticides, organic farming and bio-pesticides (neem), integrated pest management (IPM), proper disposal of industrial and hazardous waste, afforestation of mine spoils.

7. Noise Pollution

Sources and effects

• Sources: traffic (honking), industries, construction, loudspeakers/DJs, aircraft, crackers (Diwali).
• Effects: hearing loss (prolonged exposure above 85 dB), hypertension, sleep disturbance, stress, reduced concentration in children; disturbs wildlife (birds, animals).

Noise Pollution (Regulation and Control) Rules, 2000

Control: silencers/mufflers, green belts (trees absorb sound), restricted honking zones, time limits on loudspeakers (the Supreme Court restricted loudspeaker use at night), ear protection for workers.

8. Thermal and Nuclear Pollution

Thermal pollution

• Effects: warm water holds less dissolved oxygen; fish and aquatic life suffer or die; thermal shock kills organisms near outfalls; algae grow faster.
• Control: cooling ponds, cooling towers and spray ponds to cool water before discharge; cogeneration (using waste heat).

Nuclear (radioactive) pollution

• Effects: radiation damages DNA → cancer, genetic mutations, birth defects; long-lived waste stays dangerous for thousands of years.
• Control: strict reactor safety, deep geological disposal of waste, protective shielding, monitoring.
• Major accidents: Three Mile Island, USA (1979); Chernobyl, USSR/Ukraine (26 April 1986) — worst ever, reactor explosion spread radiation across Europe; Fukushima, Japan (11 March 2011) — earthquake + tsunami damaged reactors.

9. Solid Waste Management

Types of solid waste

The 4R principle and disposal methods

• 4R: Refuse, Reduce, Reuse, Recycle — refuse unnecessary items first.
• Composting / vermicomposting: biodegradable waste → manure (earthworms speed it up).
• Sanitary landfill: engineered pits with liners and leachate collection — waste buried in layers.
• Incineration: burning at high temperature (good for biomedical waste; needs pollution control for dioxins).
• Waste-to-energy: biogas from organic waste; refuse-derived fuel.
• Segregation at source (wet/dry/hazardous) is the legal starting point — Swachh Bharat Mission (2014) pushed this nationally.

Key rules

• Solid Waste Management Rules, 2016 — segregation at source, user fees, waste pickers integrated.
• Plastic Waste Management Rules, 2016 (amended 2021) — single-use plastic ban from 1 July 2022.
• E-Waste (Management) Rules, 2016 — extended producer responsibility (makers must take back old electronics).

10. Pollution Case Studies

(a) Bhopal Gas Tragedy — 2–3 December 1984

• What: highly toxic methyl isocyanate (MIC) gas leaked from the Union Carbide India Limited pesticide plant, Bhopal, Madhya Pradesh, on the night of 2–3 December 1984.
• Impact: one of the world's worst industrial disasters — thousands died within days and lakhs were exposed; survivors suffered respiratory, eye and reproductive damage for decades.
• Aftermath: led directly to the Environment (Protection) Act, 1986 and the Public Liability Insurance Act, 1991; a warning on poor industrial safety and siting of hazardous units near dense populations.

(b) Chernobyl — 26 April 1986

• Reactor explosion at Chernobyl, Ukraine (then USSR) — the worst nuclear accident in history; a large exclusion zone remains uninhabitable; thyroid cancers rose sharply in the region.

(c) London Smog — December 1952

• The Great Smog: coal smoke + fog trapped over London for days; thousands died of respiratory failure. It forced Britain's Clean Air Act, 1956 — the model for later air laws worldwide, including India's.

(d) Minamata — Japan, 1956

• Mercury discharged by the Chisso chemical factory into Minamata Bay accumulated in fish; people who ate the fish developed Minamata disease (neurological damage). A textbook case of biomagnification. (Related: Itai-itai disease from cadmium in Japan.)

11. Quick-Revision Table