Pollution, Environmental Law & International Agreements

Clean water is judged by how much oxygen it can spare for fish. Dissolved oxygen (DO) in a healthy river is about 8–10 mg/L at ordinary temperatures; most fish are stressed below 5 mg/L and die below about 2 mg/L. Biochemical oxygen demand (BOD) measures how much of that oxygen aerobic microbes will consume while decomposing the organic matter in a sample, by convention over 5 days at 20 °C (hence the symbol BOD₅). Clean river water has BOD below 3 mg/L; raw domestic sewage typically 200–400 mg/L; CPCB treats a stretch with BOD above 3 mg/L as polluted and prioritises it for restoration. Chemical oxygen demand (COD) uses a strong oxidant (potassium dichromate) to oxidise everything, biodegradable or not, so COD ≥ BOD always; a high COD/BOD ratio signals industrial rather than sewage pollution.

Worked example — computing BOD. A 300 mL BOD bottle is filled with river water diluted 1 : 10 (i.e. 30 mL sample + 270 mL aerated dilution water). Initial DO = 8.6 mg/L. After 5 days at 20 °C the DO = 4.4 mg/L. Oxygen consumed in the bottle = 8.6 − 4.4 = 4.2 mg/L. Because the sample was only one-tenth of the bottle, the dilution factor is 300 ÷ 30 = 10. BOD₅ of the river water = 4.2 × 10 = 42 mg/L — heavily polluted (about fourteen times the 3 mg/L benchmark), consistent with untreated sewage entering upstream. Notice why dilution is needed at all: had the raw sample been tested undiluted, all 8.6 mg/L of oxygen would have been exhausted before day 5 and the true demand could not be read.

Soil pollution has four exam-relevant faces.
(1) Agro-chemical residue — organochlorine pesticides such as DDT, endosulfan and aldrin are fat-soluble and persist for decades, moving up food chains by biomagnification; India banned endosulfan after the Kasaragod (Kerala) episode.
(2) Salinisation and alkalinisation — canal irrigation without drainage raises the water table, capillary action carries salts to the surface, and usar or reh land forms; a soil is called saline above an electrical conductivity of about 4 dS/m and alkaline above pH 8.5.
(3) Heavy-metal loading from sewage sludge, tannery effluent (chromium, Kanpur) and fly ash.
(4) Acidification from acid rain and ammonium fertiliser, which leaches calcium and releases aluminium. The Soil Health Card scheme reports 12 parameters — N, P, K, S, the micronutrients Zn, Fe, Cu, Mn, B, plus pH, EC and organic carbon.

Why the decibel table is not as gentle as it looks. The decibel is logarithmic: sound intensity level L = 10 × log₁₀(I ÷ I₀), where I₀ = 10⁻¹² W/m² is the threshold of hearing. Worked example: two identical generators each producing 70 dB at a point do not give 140 dB. Doubling the intensity adds 10 × log₁₀(2) = 10 × 0.301 = 3.01 dB, so the pair produces about 73 dB. Ten such generators add 10 × log₁₀(10) = 10 dB, giving 80 dB. Conversely, the gap between the residential day limit (55 dB) and the industrial day limit (75 dB) is 20 dB, i.e. 10^(20 ÷ 10) = 100 times the sound intensity. The Rules also fix loudspeaker hours (not after 10 p.m., extendable to midnight on at most 15 days a year by the State), and prolonged exposure above 85 dB causes permanent hearing loss; 120–130 dB is the pain threshold.

• Solid Waste Management Rules, 2016 replaced the 2000 Rules, extended coverage beyond municipal areas to census towns, notified areas and pilgrimage sites, and made three-stream source segregation (wet, dry, domestic hazardous) a duty of the generator. Bulk generators (over 100 kg/day) must process wet waste on site; a user fee and spot fine for littering were authorised.
• E-Waste (Management) Rules — first notified 2011, recast 2016 and again 2022. Built on Extended Producer Responsibility (EPR) with collection targets, RoHS (restriction of hazardous substances — lead, mercury, cadmium, hexavalent chromium, PBB, PBDE limited to 0.1 % by weight, cadmium 0.01 %), and registration of producers and recyclers on a CPCB portal. E-waste is the fastest-growing waste stream; a phone or CRT screen contains lead, mercury, cadmium, beryllium and brominated flame retardants.
• Plastic Waste Management Rules, 2016 raised the minimum carry-bag thickness from 40 to 50 microns (later 75 and then 120 microns by amendment), introduced EPR for producers and brand owners, and the 2021 amendment banned identified single-use plastic items — ear-buds with plastic sticks, plastic flags, candy and ice-cream sticks, thermocol decoration, plates, cups, cutlery, straws, wrapping films — from 1 July 2022.
• Hazardous and Other Wastes (Management and Transboundary Movement) Rules, 2016 — the word "other" covers waste tyres, paper, metal scrap and used electronics that are imported for recycling; import of waste for disposal is prohibited, implementing India's Basel obligations. Construction and Demolition Waste Rules, 2016 were notified for the first time in that year.

The Constitution of 1950 did not mention the environment. The 42nd Amendment Act, 1976 — passed to give effect to India's Stockholm commitments — inserted two provisions and shifted "forests" and "protection of wild animals and birds" from the State List to the Concurrent List (Entries 17A and 17B). Article 48A (Part IV, Directive Principles): "The State shall endeavour to protect and improve the environment and to safeguard the forests and wild life of the country." Article 51A(g) (Part IVA, Fundamental Duties): it is the duty of every citizen "to protect and improve the natural environment including forests, lakes, rivers and wild life, and to have compassion for living creatures." Note the asymmetry examiners test: 48A binds the State, 51A(g) binds the citizen; neither is directly enforceable, but the Supreme Court has read a right to a wholesome environment into Article 21 (Subhash Kumar v. State of Bihar, 1991) and used Article 32 public-interest petitions — M.C. Mehta's Ganga, Oleum gas and Taj cases — to enforce it, importing the polluter-pays, precautionary and public trust doctrines and the principle of absolute liability for hazardous industries.

CPCB versus SPCB — who does what. The CPCB (statutory since 1974, headquartered in Delhi, under the Ministry of Environment, Forest and Climate Change) advises the Centre, lays down national standards (NAAQS, effluent standards, the AQI methodology), runs the national monitoring networks (NAMP for air, NWMP for water), coordinates the SPCBs and settles disputes among them, and publishes the list of polluted river stretches and Critically Polluted Areas using the Comprehensive Environmental Pollution Index. An SPCB advises its State government, grants and refuses consents to industries, inspects plants, prosecutes offenders, and may prescribe stricter (never laxer) standards than the CPCB. Under the EPA the CPCB may also be directed by the Centre to exercise its powers in a State — the route used for Delhi's Graded Response Action Plan stages, which are triggered by the AQI bands: Stage I at Poor, Stage II at Very Poor, Stage III at Severe, Stage IV at "Severe+" (AQI above 450).

1. Public Liability Insurance Act, 1991 — compulsory insurance for handlers of hazardous substances so that accident victims get immediate no-fault relief; a direct child of Bhopal.
2. Biological Diversity Act, 2002 — implements the CBD; three-tier structure: National Biodiversity Authority (Chennai), State Biodiversity Boards, local Biodiversity Management Committees which keep People's Biodiversity Registers; regulates access and benefit-sharing for foreigners using Indian genetic resources.
3. Scheduled Tribes and Other Traditional Forest Dwellers (Recognition of Forest Rights) Act, 2006 — the "Forest Rights Act"; recognises individual and community forest rights and gives the Gram Sabha the key role; the counterweight to the 1980 Act's centralising thrust.
4. Compensatory Afforestation Fund Act, 2016 — created the National and State CAMPA funds from the money paid by project proponents who divert forest land; 90 % goes to the States.

UNEP and the IPCC are different kinds of body. UNEP (1972, Nairobi) is an operational UN programme: it hosts treaty secretariats (Ozone, CITES, CBD, Basel, Minamata), publishes the annual Emissions Gap Report and Global Environment Outlook, runs World Environment Day (5 June) and the Champions of the Earth award, and co-sponsors the IPCC. The IPCC (1988, Geneva, created by WMO and UNEP, endorsed by UN General Assembly resolution 43/53) is an assessment body with 195 member governments: it writes nothing new, but grades the published literature through Working Group I (physical science basis), WG II (impacts, adaptation, vulnerability), WG III (mitigation) and a Task Force on National Greenhouse Gas Inventories. Its Assessment Reports (AR1 1990, AR2 1995, AR3 2001, AR4 2007, AR5 2014, AR6 2021–23) feed the UNFCCC negotiations; the AR4 year is memorable because the IPCC shared the 2007 Nobel Peace Prize with Al Gore. The 1.5 °C Special Report (2018) is the origin of the "net zero by 2050" benchmark.

Earthquakes — two scales, one common confusion. The Richter scale (1935) measures magnitude — energy released at the focus — from seismograph amplitude; it is logarithmic to base 10, so each whole number is 10 times the ground amplitude and about 31.6 times (10^1.5) the energy. Worked example: a magnitude 7 quake versus a magnitude 5 quake — difference 2 units → amplitude 10² = 100 times; energy 10^(1.5 × 2) = 10³ = 1,000 times. Between magnitude 6 and 7, energy ratio = 10^1.5 = 31.6 times. Seismologists today report the moment magnitude (Mw), which does not saturate for great quakes; the media still say "Richter". The Modified Mercalli scale measures intensity — observed damage — in 12 grades (I–XII) and varies from place to place for the same quake. India's seismic zoning map (IS 1893) has Zones II to V; Zone V (very high damage risk, zone factor 0.36) covers Kashmir, the Himachal–Uttarakhand Himalaya, north Bihar, the whole north-east, the Andaman–Nicobar Islands and Kutch (Bhuj 2001, Mw 7.7). The focus is the underground origin; the epicentre is the surface point directly above it; P-waves arrive first, S-waves second, surface (L) waves do the damage; a tsunami follows undersea quakes of about magnitude 7 or more with vertical displacement.

• Cyclone naming: names in the north Indian Ocean are assigned by the WMO/ESCAP Panel on Tropical Cyclones, whose 13 member countries (Bangladesh, India, Iran, Maldives, Myanmar, Oman, Pakistan, Qatar, Saudi Arabia, Sri Lanka, Thailand, UAE, Yemen) each contribute 13 names to a rolling list adopted in 2020; the IMD, New Delhi, as Regional Specialised Meteorological Centre, names the storm when sustained winds reach 62 km/h (34 knots). Names are gender-neutral, not repeated, and never political or religious. IMD categories: Depression → Deep Depression → Cyclonic Storm (62–88 km/h) → Severe (89–117) → Very Severe (118–165) → Extremely Severe (166–221) → Super Cyclonic Storm (≥ 222 km/h). The same phenomenon is a hurricane in the Atlantic and east Pacific, a typhoon in the north-west Pacific, and a willy-willy in Australia.
• Flood mitigation: structural — embankments, reservoirs, channel improvement, detention basins; non-structural — flood-plain zoning, flood forecasting by the Central Water Commission (over 300 stations), flood insurance, and the National Flood Commission (Rashtriya Barh Ayog, 1980) estimate that about 40 million hectares are flood-prone. Urban floods (Mumbai 2005, Chennai 2015) come from concretisation and encroached drains rather than river spill.
• Drought: IMD calls a year a drought year when all-India rainfall is below 90 % of the long-period average (deficiency over 10 %) with more than 20 % of the area affected; meteorological drought (rainfall deficit) precedes hydrological drought (low rivers, reservoirs, groundwater) and agricultural drought (soil moisture insufficient for crops). Mitigation: watershed development, drought-resistant cultivars, drip and sprinkler irrigation, crop insurance, and the Drought Prone Areas Programme (1973) and Desert Development Programme (1977), later merged into watershed schemes.
• Landslides: triggered by rainfall saturation, earthquakes, undercutting of slopes for roads, deforestation and unplanned construction; the Geological Survey of India is the nodal agency for landslide hazard zonation, and the NDMA guidelines (2009) prescribe slope stabilisation, retaining walls, bio-engineering with deep-rooted vegetation and early-warning rain-gauge thresholds. The Himalaya, Western Ghats (Wayanad, Kodagu) and Nilgiris are the belts.

The Disaster Management Act, 2005 (enacted 23 December 2005, after the 2004 Indian Ocean tsunami) defines "disaster" to include man-made catastrophes and sets up a three-tier authority chain: NDMA (Section 3; chaired ex officio by the Prime Minister, up to nine other members, headquartered in New Delhi — lays down policies and approves the National Plan), SDMA (Section 14; chaired by the Chief Minister) and DDMA (Section 25; chaired by the District Collector with the elected local-body head as co-chair). Section 44 creates the National Disaster Response Force (NDRF) — battalions drawn from the CAPFs; Section 42 the National Institute of Disaster Management (NIDM); Sections 46–48 the National and State Disaster Response Funds and Mitigation Funds. The Act was used nationwide for the first time to impose the 2020 lockdown. India is also a signatory to the Sendai Framework 2015–2030 (four priorities: understanding risk; strengthening governance; investing in reduction; enhancing preparedness for "build back better") and adopted a National Disaster Management Plan in 2016 — the first national plan aligned with Sendai.