Air, Water, Soil and Noise Pollution: Sources, Standards and Control

Prerequisites: Ecosystems: Structure, Energy Flow and Nutrient Cycles · Environmental Pollution — overview

The Hook: The Fog That Killed a City

The Core Concept

Pollution is the undesirable change in the physical, chemical or biological characteristics of air, water or soil that harms living organisms or property. A pollutant can be:

• Primary — emitted directly (sulphur dioxide, carbon monoxide, soot), or secondary — formed in the atmosphere from primary pollutants (ground-level ozone, peroxyacetyl nitrate (PAN), sulphate and nitrate aerosols).
• Biodegradable (sewage, food waste) or non-biodegradable (heavy metals, DDT, many plastics).

Air pollution

Two kinds of smog

Acid rain is precipitation with pH below about 5.6, formed when sulphur dioxide and nitrogen oxides oxidise to sulphuric and nitric acids. It damages forests, lakes and buildings — the corrosion of marble (calcium carbonate) by acid deposition was a concern behind the Supreme Court’s orders to protect the Taj Mahal in the Taj Trapezium case (1996).

Standards and indices

• National Ambient Air Quality Standards (NAAQS), 2009 cover 12 pollutants: PM10, PM2.5, SO₂, NO₂, CO, O₃, NH₃, lead, benzene, benzo(a)pyrene, arsenic and nickel.

• National Air Quality Index (AQI), launched in April 2015, is computed from eight pollutants — PM10, PM2.5, NO₂, SO₂, CO, O₃, NH₃ and lead — and reports six categories:

Control measures

Water pollution

Sources are point (a factory outfall or a sewage drain) or non-point (diffuse runoff from farms and cities — harder to regulate).

The CPCB’s primary water-quality criteria for outdoor bathing require DO of 5 mg/L or more and BOD of 3 mg/L or less.

Eutrophication is the nutrient enrichment of a water body, mainly by nitrogen and phosphorus from fertilisers, detergents and sewage:

graph LR
    A[Nitrogen and phosphorus inflow] --> B[Algal bloom]
    B --> C[Algae die]
    C --> D[Decomposers use up dissolved oxygen]
    D --> E[Fish kills and loss of biodiversity]

When human activity speeds this up, it is called cultural or accelerated eutrophication. Some algal blooms also produce toxins.

Bioaccumulation and biomagnification

• Bioaccumulation — build-up of a substance in an organism’s body faster than it is excreted.
• Biomagnification — increase in its concentration at each higher trophic level. It happens with substances that are persistent and fat-soluble, such as DDT and methylmercury. NCERT cites high DDT concentrations in fish-eating birds, which caused thinning of eggshells and population declines.

Pollutant-linked diseases

Thermal pollution from power-plant cooling water raises water temperature, reducing dissolved oxygen.

Soil pollution and solid waste

Soil is polluted by excessive pesticides and fertilisers, heavy metals from industrial effluents and sludge, leachate from dumpsites, and e-waste. India regulates waste through a set of rules under the Environment (Protection) Act, 1986, including the Solid Waste Management Rules, 2016; Plastic Waste Management Rules, 2016; Bio-Medical Waste Management Rules, 2016; and E-Waste (Management) Rules, 2022.

Plastic waste: amendments to the Plastic Waste Management Rules in 2021 prohibited identified single-use plastic items from 1 July 2022 and raised the minimum thickness of plastic carry bags to 75 microns (from 30 September 2021) and 120 microns (from 31 December 2022). Extended Producer Responsibility (EPR) applies to producers, importers and brand owners.

Noise pollution

Under the Noise Pollution (Regulation and Control) Rules, 2000, ambient limits in dB(A) Leq are:

A silence zone is an area of at least 100 metres around hospitals, educational institutions, courts and similar places declared by the competent authority.

Memory Anchors

NAQI’s eight pollutants — “Particles (2) + SO NO CO O₃ NH₃ Pb”: PM10, PM2.5, SO₂, NO₂, CO, O₃, NH₃, lead. Carbon dioxide is not one of them.

Japan’s two metal diseases — “Mercury is Minamata, Cadmium makes you cry Itai-itai” (itai means “it hurts”).

BOD rule of thumb: “Big Organic Dirt → Big BOD.” Clean water has low BOD and high DO.

One-line Mains hook: Air pollution is a problem of airsheds, not cities — it needs regional governance, not municipal boundaries.

For Prelims

For Mains

• Dimensions: health (respiratory and cardiovascular disease, child development), economic (lost labour productivity, health costs, tourism), governance (Centre–State–municipal coordination; airshed management; weak enforcement capacity of pollution control boards), agricultural (crop-residue burning, fertiliser overuse), equity (the poor face more exposure and have less protection).
• Keywords: airshed, source apportionment, non-attainment city, secondary aerosols, extended producer responsibility, circular economy, faecal sludge management, zero liquid discharge, polluter pays.
• Value-addition: WHO’s 2021 tightening of air quality guidelines; NCAP and its performance-linked funding; the CAQM as a regional body; London’s 1952 smog and the Clean Air Act, 1956 as evidence that sustained regulation works.

Common Traps

In the News

• July 2022 — ban on identified single-use plastic items took effect.
• See current affairs for winter air quality, GRAP stages and river pollution updates.

Practice

Prelims

Mains

Quick Revision

Key Takeaways

Related Topics

• Environmental Pollution — quick revision
• Environmental Pollution — practice questions
• Environmental Laws and Institutions
• Climate Change
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