🔊 Chapter 05 · Topic 04 · Environmental Pollution
Noise & Radioactive Pollution
Noise pollution — decibel levels, health effects, standards. Radioactive pollution — sources, nuclear accidents, waste management — complete UPSC & PSC notes.
🔊 Noise Pollution
Noise pollution is unwanted or excessive sound that disrupts the environment and causes harm to human health and wildlife. It is measured in decibels (dB) on a logarithmic scale.
Key Decibel Reference Points
| Sound Level (dB) | Source | Effect |
|---|---|---|
| 0 dB | Threshold of hearing | Barely audible |
| 30 dB | Whisper | Very quiet |
| 60 dB | Normal conversation | Comfortable |
| 85 dB | Heavy traffic, factory | Prolonged exposure causes hearing loss |
| 100 dB | Jackhammer, nightclub | Hearing damage in minutes |
| 120 dB | Threshold of pain (jet engine) | Immediate pain; hearing damage |
| 140+ dB | Gunshot, explosion | Immediate permanent hearing damage |
Noise Standards — India (Noise Pollution Rules 2000)
| Zone | Day (6 AM–10 PM) | Night (10 PM–6 AM) |
|---|---|---|
| Industrial | 75 dB | 70 dB |
| Commercial | 65 dB | 55 dB |
| Residential | 55 dB | 45 dB |
| Silence Zone (hospitals, schools, courts) | 50 dB | 40 dB |
⭐ Key Rule: Noise Pollution (Regulation and Control) Rules 2000 were issued under the Environment Protection Act 1986. Silence zones extend 100 metres around hospitals, educational institutions, courts, and religious places. Loudspeakers require permission from authorities.
Sources of Noise Pollution
- Transportation — road traffic (most common), aircraft, railways
- Industrial — machinery, compressors, generators
- Construction — drilling, pile driving, demolition
- Social/cultural — loudspeakers, firecrackers, public events
- Domestic — TV, music systems, household appliances
Health Effects of Noise Pollution
- Auditory effects: Noise-Induced Hearing Loss (NIHL) — permanent damage to hair cells in cochlea; tinnitus (ringing in ears)
- Non-auditory effects: hypertension, cardiovascular disease, sleep disturbance, stress, anxiety, reduced concentration and productivity
- Effects on wildlife: disrupts communication, navigation (whales, dolphins), breeding behaviour; causes habitat abandonment
- WHO recommends night-time noise levels below 40 dB for healthy sleep
Noise Pollution Control
- Engineering controls: sound barriers, noise-absorbing materials, vibration isolation, mufflers
- Administrative controls: zoning laws, time restrictions on noisy activities, vehicle noise standards
- Personal protection: earplugs, earmuffs for workers in noisy environments
- Green belts: trees and shrubs absorb and deflect sound — effective noise barriers
- Supreme Court guidelines on firecrackers — only “green crackers” allowed; time restrictions
☢️ Radioactive Pollution
Radioactive pollution is contamination of the environment with radioactive substances that emit ionising radiation (alpha, beta, gamma rays, neutrons).
Types of Ionising Radiation
| Type | Nature | Penetrating Power | Shielding |
|---|---|---|---|
| Alpha (α) | Helium nucleus (2p + 2n) | Lowest — stopped by paper/skin | Paper, skin |
| Beta (β) | Electron or positron | Medium — penetrates skin | Aluminium sheet |
| Gamma (γ) | Electromagnetic radiation | Highest — penetrates body | Lead, thick concrete |
| Neutron | Neutral particle | Very high — penetrates deeply | Water, polyethylene |
Sources of Radioactive Pollution
- Nuclear power plants — routine low-level releases; accidents (Chernobyl, Fukushima)
- Nuclear weapons testing — atmospheric tests released large amounts of radioactive fallout (1945–1963)
- Mining of radioactive ores — uranium, thorium mining; radon gas release
- Medical use — X-rays, CT scans, nuclear medicine (diagnostic and therapeutic)
- Industrial use — radiography, gauges, smoke detectors (Americium-241)
- Natural sources — cosmic radiation, radon gas from soil (major indoor radiation source), naturally occurring radioactive materials (NORM)
Health Effects of Radioactive Pollution
- Acute radiation syndrome — high-dose exposure; nausea, hair loss, organ failure, death
- Cancer — leukaemia, thyroid cancer, lung cancer (from radon)
- Genetic mutations — damage to DNA; heritable mutations
- Birth defects — exposure during pregnancy
- Radiation burns — skin damage from high-dose exposure
Major Nuclear Accidents
| Accident | Year | Location | Key Facts |
|---|---|---|---|
| Chernobyl | 1986 | Ukraine (then USSR) | Reactor explosion; 30 immediate deaths; 600,000 exposed; exclusion zone still exists; worst nuclear accident |
| Fukushima Daiichi | 2011 | Japan | Triggered by tsunami; 3 reactors melted down; 154,000 evacuated; INES Level 7 (same as Chernobyl) |
| Three Mile Island | 1979 | USA | Partial meltdown; no immediate deaths; INES Level 5; led to stricter nuclear regulations in USA |
| Bhopal Gas Tragedy | 1984 | India | Not nuclear — MIC (methyl isocyanate) gas leak from Union Carbide plant; 3,000+ immediate deaths; led to EPA 1986 |
📌 INES Scale: International Nuclear Event Scale — rates nuclear events from 0 (no safety significance) to 7 (major accident). Chernobyl and Fukushima are the only Level 7 events. Three Mile Island was Level 5.
Nuclear Waste Management
- Low-level waste (LLW) — contaminated clothing, tools; stored in near-surface repositories
- Intermediate-level waste (ILW) — reactor components, resins; requires shielding
- High-level waste (HLW) — spent nuclear fuel; highly radioactive; requires deep geological disposal
- Half-life — time for radioactivity to reduce by half; HLW can remain dangerous for thousands of years (e.g., Plutonium-239 half-life = 24,100 years)
- India’s nuclear waste managed by BARC (Bhabha Atomic Research Centre), Mumbai
- Atomic Energy Regulatory Board (AERB) — India’s nuclear safety regulator
✅ Revision Checklist — Noise & Radioactive Pollution
✅ Noise measured in decibels (dB) — logarithmic scale
✅ 85 dB = prolonged exposure causes hearing loss; 120 dB = threshold of pain
✅ Silence zone = 50 dB day / 40 dB night (hospitals, schools, courts)
✅ Residential = 55 dB day / 45 dB night
✅ Noise Pollution Rules 2000 = under EPA 1986
✅ NIHL = Noise-Induced Hearing Loss = permanent damage to cochlear hair cells
✅ Green belts = trees absorb and deflect sound
✅ Alpha = lowest penetration (paper); Gamma = highest (needs lead shielding)
✅ Chernobyl (1986) = Ukraine = worst nuclear accident = INES Level 7
✅ Fukushima (2011) = Japan = tsunami-triggered = INES Level 7
✅ Three Mile Island (1979) = USA = INES Level 5
✅ Bhopal (1984) = MIC gas leak = not nuclear = led to EPA 1986
✅ HLW = high-level waste = deep geological disposal = most dangerous
✅ BARC = Bhabha Atomic Research Centre = manages India’s nuclear waste
✅ AERB = Atomic Energy Regulatory Board = India’s nuclear safety regulator
✅ Radon gas = natural radioactive source = major indoor radiation source
✅ 85 dB = prolonged exposure causes hearing loss; 120 dB = threshold of pain
✅ Silence zone = 50 dB day / 40 dB night (hospitals, schools, courts)
✅ Residential = 55 dB day / 45 dB night
✅ Noise Pollution Rules 2000 = under EPA 1986
✅ NIHL = Noise-Induced Hearing Loss = permanent damage to cochlear hair cells
✅ Green belts = trees absorb and deflect sound
✅ Alpha = lowest penetration (paper); Gamma = highest (needs lead shielding)
✅ Chernobyl (1986) = Ukraine = worst nuclear accident = INES Level 7
✅ Fukushima (2011) = Japan = tsunami-triggered = INES Level 7
✅ Three Mile Island (1979) = USA = INES Level 5
✅ Bhopal (1984) = MIC gas leak = not nuclear = led to EPA 1986
✅ HLW = high-level waste = deep geological disposal = most dangerous
✅ BARC = Bhabha Atomic Research Centre = manages India’s nuclear waste
✅ AERB = Atomic Energy Regulatory Board = India’s nuclear safety regulator
✅ Radon gas = natural radioactive source = major indoor radiation source