Environment & Ecology
Environmental Pollution
GS Paper III
Environmental Pollution — Quick Revision
One-page UPSC revision of pollution: NAAQS and AQI, smog types, acid rain, BOD and COD, eutrophication, biomagnification, pollutant diseases, noise limits and waste rules.
SyllabusGS III · Conservation, environmental pollution and degradation (GS III); general issues on environmental ecology (Prelims)
A last-week revision sheet for pollution. Numbers and look-alike pairs are what Prelims tests here.
Air
| Item | Key fact |
|---|---|
| Primary pollutants | SO₂, NOₓ, CO, particulate matter, lead |
| Secondary pollutants | Ground-level O₃, PAN, sulphate and nitrate aerosols |
| NAAQS (2009) | 12 pollutants: PM10, PM2.5, SO₂, NO₂, CO, O₃, NH₃, Pb, benzene, benzo(a)pyrene, arsenic, nickel |
| National AQI (April 2015) | 8 pollutants: PM10, PM2.5, NO₂, SO₂, CO, O₃, NH₃, Pb |
| AQI bands | Good, Satisfactory, Moderately polluted, Poor, Very poor, Severe |
| PM2.5 limits | NAAQS 40 (annual) / 60 (24 h); WHO 2021: 5 / 15 µg/m³ |
| PM10 limits | NAAQS 60 / 100; WHO 2021: 15 / 45 µg/m³ |
| Acid rain | pH below about 5.6; from SO₂ and NOₓ |
| NCAP | January 2019; non-attainment cities |
| CAQM | Statutory, 2021 Act; Delhi-NCR and adjoining areas |
| BS-VI | Nationwide 1 April 2020 |
Smog
| Classical | Photochemical | |
|---|---|---|
| Ingredients | Smoke, SO₂ | NOₓ + hydrocarbons + sunlight |
| Weather | Cool, humid | Warm, sunny |
| Nature | Reducing | Oxidising |
| Typical case | London, 1952 | Los Angeles |
Water
| Item | Key fact |
|---|---|
| BOD | Oxygen used by microbes for organic matter; high BOD = polluted |
| COD | Oxygen for chemical oxidation of all matter; generally ≥ BOD |
| Bathing water (CPCB) | DO ≥ 5 mg/L; BOD ≤ 3 mg/L |
| Eutrophication | Excess N and P → algal bloom → low DO → fish kill |
| Biomagnification | Persistent, fat-soluble toxins rise up the food chain (DDT, methylmercury) |
| Thermal pollution | Warm effluents reduce dissolved oxygen |
Diseases
| Disease | Pollutant |
|---|---|
| Minamata | Mercury |
| Itai-itai | Cadmium |
| Blue baby syndrome | Nitrate |
| Fluorosis | Fluoride |
| Black foot disease / arsenicosis | Arsenic |
Noise Limits (dB(A) Leq, Rules of 2000)
| Zone | Day | Night |
|---|---|---|
| Industrial | 75 | 70 |
| Commercial | 65 | 55 |
| Residential | 55 | 45 |
| Silence | 50 | 40 |
Waste Rules (under the Environment (Protection) Act, 1986)
| Rules | Remember |
|---|---|
| Solid Waste Management Rules, 2016 | Source segregation |
| Plastic Waste Management Rules, 2016 (amended 2021) | SUP ban from 1 July 2022; carry bags 120 microns from 31 December 2022; EPR for producers, importers, brand owners |
| Bio-Medical Waste Management Rules, 2016 | Colour-coded segregation |
| E-Waste (Management) Rules, 2022 | EPR for producers |
High-yield facts
- CO is in the AQI; CO₂ is not.
- Ozone: protective in the stratosphere, a pollutant in the troposphere.
- Lichens are indicators of SO₂ pollution.
- The Taj Trapezium case (1996) addressed pollution threatening the Taj Mahal.
Traps
- High BOD does not mean clean water.
- Photochemical smog needs sunlight; it is oxidising, not reducing.
- Biomagnification does not occur with rapidly degraded, water-soluble substances.
Related Topics
- Air, Water, Soil and Noise Pollution: Sources, Standards and Control
- Environmental Pollution — practice questions
- Environmental Laws and Institutions — quick revision
- All quick revision sheets
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