- Pollution is any undesirable change in the physical, chemical or biological character of air, water or land that harms living organisms.
- India's environmental law framework grew after the Stockholm Conference (1972) and the Bhopal gas tragedy (1984).
- The Constitution adds two duties: Article 48A (a Directive Principle to protect the environment) and Article 51A(g) (a Fundamental Duty), both inserted by the 42nd Amendment (1976).
The National Air Quality Index (2014)
India's AQI, launched in 2014, is based on eight pollutants: PM10, PM2.5, NO₂, SO₂, CO, O₃, NH₃ and lead (Pb). The worst-performing pollutant sets the day's index.
| AQI | Category | Health impact |
|---|---|---|
| 0–50 | Good | Minimal |
| 51–100 | Satisfactory | Minor breathing discomfort for sensitive people |
| 101–200 | Moderately polluted | Discomfort for people with lung or heart disease |
| 201–300 | Poor | Breathing discomfort for most people on prolonged exposure |
| 301–400 | Very poor | Respiratory illness on prolonged exposure |
| 401–500 | Severe | Affects healthy people; serious impact on those with disease |
Major Air Pollutants
- PM2.5 — particles under 2.5 micrometres; reach deep into the lungs and bloodstream.
- CO — binds to haemoglobin about 200 times more strongly than oxygen, forming carboxyhaemoglobin.
- SO₂ and NOₓ — cause acid rain (pH below 5.6); acid rain has damaged the marble of the Taj Mahal ("marble cancer").
- Ground-level ozone — a secondary pollutant formed from NOₓ and hydrocarbons in sunlight; a component of photochemical smog.
AQI launched2014
AQI pollutants8
Water Act1974
Air Act1981
EPA1986
NGT2010
Water Pollution
- Biological Oxygen Demand (BOD) is the oxygen microbes need to decompose organic matter in water. High BOD = more pollution. The CPCB criterion for outdoor bathing water is a BOD of 3 mg/L or less.
- Eutrophication: runoff rich in nitrates and phosphates (fertilisers, sewage) causes algal blooms, which use up dissolved oxygen when they decay and kill fish.
- Biomagnification: non-biodegradable toxins such as DDT and mercury become more concentrated at each higher trophic level — top predators like fish-eating birds are hit hardest (DDT thinned their eggshells).
Pollution-Linked Diseases
| Disease | Cause |
|---|---|
| Minamata disease | Mercury (Minamata Bay, Japan, 1950s) |
| Itai-itai disease | Cadmium (Japan) |
| Blue baby syndrome | Excess nitrate in drinking water |
| Fluorosis | Excess fluoride in water |
| Blackfoot disease / arsenicosis | Arsenic in groundwater (e.g., parts of West Bengal and Bihar) |
| Silicosis | Inhaling silica dust (mining, stone cutting) |
Key Environmental Laws
| Law | Year | What it did |
|---|---|---|
| Wild Life (Protection) Act | 1972 | Protected areas and species schedules (cut to four schedules by the 2022 amendment) |
| Water (Prevention and Control of Pollution) Act | 1974 | Created the Central Pollution Control Board and state boards |
| Forest (Conservation) Act | 1980 | Central approval needed to divert forest land; renamed the Van (Sanrakshan Evam Samvardhan) Adhiniyam by the 2023 amendment |
| Air (Prevention and Control of Pollution) Act | 1981 | Gave the pollution control boards power over air quality |
| Environment (Protection) Act | 1986 | Umbrella law passed after the Bhopal tragedy; basis for most pollution rules and EIA |
| Biological Diversity Act | 2002 | Implements the CBD; amended in 2023 |
| National Green Tribunal Act | 2010 | Set up the NGT, with its principal bench in New Delhi, to decide environmental cases |
| Commission for Air Quality Management Act | 2021 | Statutory body for air quality in the NCR and adjoining areas |
Single-use plastics: a list of identified single-use plastic items was banned across India from July 1, 2022 under the Plastic Waste Management Rules.
- Pollutant ↔ disease matching: mercury/Minamata, cadmium/itai-itai, nitrate/blue baby, fluoride/fluorosis.
- Act ↔ year chronology: 1972 → 1974 → 1980 → 1981 → 1986 → 2002 → 2010.
- Concept statements: "Higher BOD means cleaner water" — false.
Q1. A high Biological Oxygen Demand (BOD) in a river indicates:
✅ Answer: (c) High organic pollution
💡 Explanation: High BOD means microbes need a lot of oxygen to break down organic waste — a sign of pollution.
Q2. Minamata disease is caused by:
✅ Answer: (a) Mercury
💡 Explanation: It was first identified in Minamata, Japan, from mercury-contaminated fish.
Q3. The Central Pollution Control Board was constituted under the:
✅ Answer: (b) Water (Prevention and Control of Pollution) Act, 1974
💡 Explanation: The CPCB was set up in 1974 under the Water Act and later given powers under the Air Act.
Q4. Which of these is NOT one of the eight pollutants in India's National AQI?
✅ Answer: (d) Methane
💡 Explanation: The eight are PM10, PM2.5, NO₂, SO₂, CO, O₃, NH₃ and Pb; methane is not included.
Q5. Articles 48A and 51A(g) on environmental protection were added by the:
✅ Answer: (b) 42nd Amendment
💡 Explanation: The 42nd Amendment of 1976 inserted both provisions.
🔁 Revise in 60 Seconds
- AQI 2014: 8 pollutants, 6 categories (Good to Severe, 0–500).
- High BOD = polluted; eutrophication = nutrient overload → algal bloom → oxygen loss.
- Mercury → Minamata; cadmium → itai-itai; nitrate → blue baby; fluoride → fluorosis.
- Acts: Wildlife 1972, Water 1974, Forest 1980, Air 1981, EPA 1986, BD 2002, NGT 2010.
📌 Prelims Traps to Avoid
- ✘ Ozone is harmful at ground level but protective in the stratosphere.
- ✘ The EPA (1986) came after Bhopal (1984), not before.
- ✘ Acid rain has a pH below 5.6, not below 7 — normal rain is already slightly acidic.
What are the AQI categories in India?
Six: Good (0–50), Satisfactory (51–100), Moderately polluted (101–200), Poor (201–300), Very poor (301–400) and Severe (401–500). The index uses eight pollutants, and the worst one sets the value.
What is biomagnification?
The increase in concentration of a non-biodegradable toxin, such as DDT or mercury, at each successive level of a food chain. Top predators therefore carry the highest levels.