Environmental Pollution - 2 - Environment for UPSC CSE

What is Water Pollution?

Water pollution occurs when harmful substances-chemicals, physical agents or microorganisms-contaminate a stream, river, lake, ocean, aquifer or other body of water, degrading its quality and rendering it toxic or unsuitable for human use and for the needs of ecosystems.

1. Sources

➤ Types of sources

• Point sources: Pollution originating from a single, identifiable location (for example, a pipe discharging effluent into a river). Point sources are generally easier to monitor and regulate.
• Diffuse (non-point) sources: Pollution arising from many dispersed activities across the landscape (for example, agricultural runoff). These vary spatially and temporally and are more difficult to regulate.
• Community wastewater: Sewage and domestic effluents from houses, commercial and institutional establishments. Sewage contains human and animal excreta, food residues, cleaning agents and detergents. Putrefaction is the microbial decomposition of organic matter in water that consumes dissolved oxygen.
• Industrial wastes: Effluents from factories and processing plants that may contain inorganic and organic toxicants, heavy metals and persistent chemicals harmful to aquatic life and humans.
• Agricultural sources: Excess fertilisers (nitrogen, phosphorus, potassium) and pesticides (insecticides, fungicides, herbicides and others) reach water bodies by runoff, drainage and leaching. Many pesticides contain persistent compounds (e.g. chlorinated hydrocarbons, organophosphates) whose residues remain in the environment. Animal wastes from piggeries, poultry farms and slaughterhouses also enter watercourses during rains.
• Thermal pollution: Cooling water from thermal and nuclear power plants, when discharged at elevated temperatures, reduces dissolved oxygen (DO) and can stress or kill aquatic organisms.
• Groundwater contamination: Seepage from industrial and municipal waste, poorly designed septic systems, sewage channels and agricultural leaching can threaten groundwater quality.
• Marine pollution: Oceans receive pollutants via river discharge, direct dumping of sewage and garbage from coastal cities, oil spills, navigational discharges, offshore oil operations and radioactive wastes. Oceans are often the ultimate sink for many pollutants.

➤ Oil spills

• Oil spills are among the most harmful forms of water pollution because oil spreads quickly over large surface areas and affects multiple compartments (surface water, shorelines and biota).
• Spills occur from tankers, pipelines, offshore facilities and storage tanks; crude oil floats on water, can form flammable films and reduces oxygen exchange at the surface.
• Oil contamination causes mortality and sublethal effects in fish, birds and marine mammals, and oil residues can persist in sediments and food chains.
• On land, pipeline leaks and tanker accidents contaminate soils and groundwater.
• Remedial options include mechanical recovery, dispersants, bioremediation using oil-degrading microorganisms and absorbents (e.g. sawdust-like material such as bregoli) among other measures.

2. Effects of Water Pollution

(i) Effects on aquatic ecosystems

• Pollution reduces dissolved oxygen (DO), eliminating oxygen-sensitive organisms such as plankton, molluscs and many fish species.
• Some tolerant species (for example, the annelid Tubifex and certain insect larvae) survive in low-DO conditions and serve as indicator species of pollution.
• Biocides, polychlorinated biphenyls (PCBs) and heavy metals directly kill or bioaccumulate in aquatic organisms.
• Thermal discharges lower DO and alter species composition and life cycles of aquatic fauna.

➤ What are DO, BOD and COD?

• Dissolved oxygen (DO) is the concentration of oxygen dissolved in water, essential for aquatic life. Water having DO below 8.0 mg L-1 may be considered contaminated; DO below 4.0 mg L-1 indicates highly polluted water. DO depends on surface turbulence, photosynthesis, respiration and decomposition rates.
• Biochemical oxygen demand (BOD) is the amount of dissolved oxygen required by microorganisms to decompose biodegradable organic matter. BOD is expressed in mg O2 L-1. Higher BOD implies greater oxygen consumption and lower DO in water.
• Chemical oxygen demand (COD) measures the oxygen equivalent of the total quantity of organic matter (both biodegradable and non-biodegradable) that can be oxidised chemically. COD gives a more comprehensive estimate of organic pollution than BOD.

(ii) Effects on human health

• Contaminated water commonly contains pathogens (viruses, bacteria, protozoa and helminths) and causes water-borne diseases such as cholera, typhoid, jaundice and amoebiasis.
• Bacterial methylation of mercury produces methylmercury, a neurotoxin that can cause numbness, vision impairment and mental disorders.
• Minamata disease-severe neurological damage from methylmercury poisoning-was first detected in Minamata Bay, Japan, in 1952 following industrial mercury discharge and fish contamination.
• Cadmium contamination of water has caused itai-itai disease (painful bone and joint disorder) and is linked to kidney, lung and liver damage and cancer.
• Lead compounds in water can cause anaemia, headaches, muscular weakness and neurological symptoms, including developmental impacts in children.

(iii) Hazards of groundwater pollution

• Excess nitrate in drinking water is dangerous, especially to infants. Nitrate reduces the oxygen-carrying capacity of blood by converting haemoglobin to methaemoglobin, causing methemoglobinemia (commonly called blue baby syndrome).
• Excess fluoride causes dental and skeletal fluorosis (neuro-muscular disorders, gastrointestinal problems, teeth mottling and bone hardening). High fluoride concentrations are reported in drinking water in 13 states of India. The maximum desirable limit is 1.5 mg L-1; long-term ingestion causes fluorosis.
• Overexploitation of groundwater can mobilise arsenic from soils and rocks into aquifers. Chronic arsenic exposure causes skin lesions, peripheral neuropathy, diarrhoea, gangrene (black foot disease) and is associated with lung and skin cancers.
• Arsenic contamination in tube-well water of the Ganges Delta, West Bengal, is a major public-health crisis. A 2007 study estimated that over 137 million people in more than 70 countries are probably affected by arsenic in drinking water.

(iv) Biological magnification

• Biological magnification (bioaccumulation and biomagnification) is the progressive increase in concentration of persistent toxic substances (for example, DDT, mercury, PCBs) at successive trophic levels in a food chain, leading to greatest burdens in top predators, including humans.

(v) Eutrophication

• Eutrophication is the enrichment of water by nutrients (mainly nitrogen and phosphorus) that leads to excessive algal and plant growth, algal blooms, oxygen depletion on decomposition and consequent fish kills and loss of biodiversity. Major causes include runoff of fertilisers, sewage discharge and detergent residues.

3. Control Measures for Water Pollution

• Establish and maintain riparian buffers (vegetated strips) to reduce runoff of sediments, nutrients and pesticides into watercourses.
• Treat municipal sewage and industrial effluents to meet prescribed standards before discharge.
• Cool thermal effluents from power plants before discharge or use closed-cycle cooling to reduce thermal pollution.
• Prohibit domestic washing and cleaning in drinking-water tanks, streams and rivers supplying water for consumption.
• Reduce excessive use of chemical fertilisers and pesticides; promote integrated pest management and precision application to limit runoff.
• Encourage organic farming and the management of animal residues to minimise pollution.
• Use aquatic plants such as water hyacinth judiciously in constructed wetlands and sewage treatment systems to remove certain heavy metals and nutrients (with proper management to avoid invasive spread).
• Respond to oil spills with mechanical recovery, absorbents, biodegradation methods and specialised sorbents; use containment booms and skimmers offshore.

➤ Steps taken by government authorities to address water pollution

• Preparation of action plans by state governments for sewage management and restoration of water quality in aquatic resources.
• Installation of Online Effluent Monitoring Systems to check direct discharge of effluents into rivers and water bodies.
• Establishment of monitoring networks for assessment of water quality.
• Regulatory action by State Pollution Control Boards / Pollution Control Committees to ensure compliance with effluent standards and improve river water quality.
• Financial assistance for installation of Common Effluent Treatment Plants (CETPs) for clusters of small-scale industrial units.
• Issuance of directions for implementation of Zero Liquid Discharge where applicable.
• Use of powers under environmental statutes (for example, the Environment (Protection) Act, 1986 and the Water (Prevention and Control of Pollution) Act, 1974) to direct industries and public agencies to prevent pollution.

Soil Pollution

Soil is the thin layer of organic and inorganic materials covering the Earth's rocky surface. Soil pollution is the addition of persistent toxic compounds, chemicals, salts, radioactive materials or pathogens to soil in amounts that adversely affect its physical, chemical and biological properties and reduce its productivity.

➤ Causes

• Indiscriminate and excessive use of chemical fertilisers, pesticides, insecticides and herbicides.
• Dumping and improper disposal of large quantities of municipal and industrial solid waste.
• Deforestation and accelerated soil erosion.
• Pollution due to rapid urbanisation and construction activity.

➤ Sources

• Industrial wastes: Heavy metals and chemicals such as mercury, lead, copper, zinc, cadmium, cyanides, chromates, acids, alkalis and organic compounds.
• Pesticides: Insecticides, fungicides, rodenticides and weedicides used in agriculture, forestry and horticulture.
• Fertilisers and manures: Overuse of chemical fertilisers reduces populations of beneficial soil organisms, harms soil structure and increases salinity.
• Discarded materials: Construction debris, plastics, glass, metals, food waste, paper and carcasses.
• Radioactive wastes: Tailings and wastes from mining and nuclear installations that enter soils via water or atmospheric deposition.
• Other pollutants: Acid rain and airborne pollutants as well as weathering of certain rocks add toxic substances to soil.

➤ Types of soil pollution

• Agricultural soil pollution from fertilisers and pesticides.
• Industrial contamination from effluents and solid waste.
• Urban soil pollution linked with municipal solid waste, sewage and construction activities.

Effects of soil pollution

(i) Agriculture

• Reduced soil fertility and loss of soil organic matter.
• Decline in biological nitrogen fixation and beneficial soil organisms.
• Increased soil erosion and loss of nutrients.
• Reduced crop yields and increased salinity where salts accumulate.
• Deposition of silt and pollutants in tanks and reservoirs, affecting water storage.

(ii) Health

• Toxic chemicals can leach into groundwater and enter human food chains.
• Biomagnification of persistent pollutants (for example, heavy metals, DDT) affects human health.
• Decomposition of organic wastes can release noxious gases and pathogens.
• Radioactive contamination of soils causes long-term health hazards.

(iii) Environment

• Loss of vegetation, decline in biodiversity and imbalance in soil fauna and flora.
• Disruption of ecosystem services such as nutrient cycling and water filtration.

(iv) Urban areas

• Clogging of drains and inundation due to dumped solid waste.
• Foul odours and generation of landfill gases.
• Challenges in solid waste management and public-health risks.

➤ Control measures for soil pollution

• Reduce use of chemical fertilisers and synthetic pesticides; promote integrated nutrient and pest management.
• Use biopesticides and biofertilisers and adopt organic farming where feasible.
• Apply the Four R's-Refuse, Reduce, Reuse and Recycle-to reduce solid-waste generation and resource consumption.
• Afforestation and reforestation to stabilise soils and prevent erosion.
• Treatment and safe disposal of industrial and municipal solid wastes; promote scientifically managed landfills and waste-to-energy where appropriate.
• Reduce waste generation at construction sites and ensure proper management of construction and demolition debris.

➤ The Four R's - brief guidance

• Refuse: Avoid purchasing unnecessary or disposable items; choose durable goods and avoid products with excessive packaging.
• Reduce: Minimise the generation of waste by careful purchase, efficient use and avoiding single-use products.
• Reuse: Use items again wherever possible (for example, repurpose jars, containers and bottles instead of discarding them).
• Recycle: Segregate waste so recyclable material (paper, glass, metals, plastics) can be collected and processed into new products; use reusable shopping bags (cloth or jute).

Noise Pollution

Noise pollution is unwanted or harmful sound created by people or machines that can be annoying, distracting, intrusive and physically harmful. Common sources include road traffic, aircraft, construction equipment, industrial machinery, garbage collection vehicles, leaf blowers and loudspeakers.

➤ Measurement and standards

• Sound is measured in decibels (dB). An increase of about 10 dB roughly doubles the perceived loudness.
• Prolonged exposure to noise levels above about 75 dB can damage hearing. The World Health Organization recommends indoor sound levels below 30 dB for good sleep environments.

➤ Ambient noise level monitoring

• The Noise Pollution (Control and Regulation) Rules, 2000 define ambient noise standards for various areas.
• In March 2011, the Government of India launched a Real-time Ambient Noise Monitoring Network. In phase-I, five Remote Noise Monitoring Terminals were installed in different noise zones in seven metropolitan cities: Delhi, Hyderabad, Kolkata, Mumbai, Bengaluru, Chennai and Lucknow.
• Phase II envisaged installation of another 35 monitoring stations in the same seven cities, and Phase III planned to install 90 stations across 18 other cities.
• Phase-III cities listed include Kanpur, Pune, Surat, Ahmedabad, Nagpur, Jaipur, Indore, Bhopal, Ludhiana, Guwahati, Dehradun, Thiruvananthapuram, Bhubaneswar, Patna, Gandhinagar, Ranchi, Amritsar and Raipur.
• Silence zones are areas not less than 100 metres around hospitals, educational institutions, courts, places of worship and any other area declared as such by a competent authority.

➤ Impacts of noise

• Annoyance: Intermittent and aperiodic sounds cause displeasure and stress.
• Physiological effects: Noise affects breathing pattern, blood pressure, heart rate and can raise cholesterol levels.
• Hearing loss: Long-term exposure to high sound levels causes permanent hearing impairment.
• Human performance: Noise distracts attention and reduces productivity and concentration.
• Nervous system: Persistent noise can cause tinnitus (ringing in the ears), fatigue and reduced mental performance.
• Sleep disturbance: Night-time noise leads to sleeplessness, restlessness and impaired daytime functioning.
• Material damage: Low-frequency infrasound or ultrasonic vibrations can damage buildings and materials in extreme cases.

➤ Control measures

The techniques for noise control can be broadly classified into three categories:

(i) Control at source

• Improve maintenance of vehicles and machinery to reduce noise emissions.
• Use quieter equipment and enforce emission standards for industries and transport.
• Restrict use of loudspeakers and control fireworks and other noisy activities by regulation.
• Control vibration through isolation and proper equipment mounting.

(ii) Control in the transmission path

• Install acoustic barriers (noise walls) along highways and around noisy installations.
• Design buildings with sound-insulating materials and layouts.
• Develop green belts (planting trees and shrubs) to provide a sound-absorbing buffer.

(iii) Protective measures for people

• Use of personal protective equipment (ear muffs, ear plugs) where occupational exposure is high.
• Reduce exposure time through job rotation and administrative controls.
• Regular monitoring and documentation of noise levels, public awareness and enforcement of standards.

Radioactive Pollution

Radioactivity is the spontaneous emission of particles (alpha, beta) and electromagnetic radiation (gamma rays) due to the disintegration of certain unstable atomic nuclei. When released into the environment, these emissions cause radioactive pollution.

➤ Types of radiation and particles

• Alpha particles (α): Positively charged helium nuclei; low penetration power and can be stopped by a sheet of paper or human skin, but dangerous if ingested or inhaled.
• Beta particles (β): High-speed electrons (or positrons) with greater penetration than alpha particles; can penetrate skin and are stopped by thin metal or glass.
• Gamma rays (γ): Electromagnetic radiation with very high penetration power; can pass through human tissue and require dense shielding (thick concrete or lead) to attenuate.
• Non-ionising radiations (for example, ultraviolet light) have lower penetration and act mainly on the absorbing tissues.
• Ionising radiations (X-rays, cosmic rays, nuclear radiations) have sufficient energy to break molecular bonds and ionise atoms, causing biological damage.

➤ Sources

Natural sources

• Cosmic rays from outer space and radionuclides present in the earth's crust such as radium-224, uranium-238, thorium-232, potassium-40 and carbon-14.

Human-made sources

Atomic explosions (nuclear fallout): Nuclear weapons and tests eject radioactive particles high into the atmosphere; these are transported widely by winds and deposited as fallout, containing radionuclides such as strontium-90, caesium-137 and iodine-131.

• Nuclear power plants (routine releases and potential accidents).
• Nuclear weapons and military uses.
• Transportation and handling of nuclear material.
• Disposal and leakage of nuclear waste.
• Uranium mining and milling.
• Medical and industrial uses (radiation therapy, certain diagnostics and sterilisation processes).

➤ Effects of radioactive pollutants

• Effects depend on the radionuclide's half-life, energy emission, rate of dispersion, deposition and environmental conditions (wind, rainfall, temperature).
• Ionising radiation causes molecular damage, leading to immediate effects (burns, acute radiation syndrome) and long-term effects (mutations, cancers, reduced life span and reproductive effects).
• Rapidly dividing cells (embryos, foetuses, bone marrow, intestinal lining and gamete-forming cells) are particularly radiosensitive.
• Certain organisms bioaccumulate specific radionuclides (for example, oysters may accumulate 65Zn, fish may concentrate 55Fe, some marine organisms deposit 90Sr).

➤ Period of radioactivity (half-life)

Each radioactive nuclide decays at a characteristic rate. The half-life is the time required for half the atoms in a sample to decay. Half-lives range from fractions of a second to thousands of years. Radionuclides with long half-lives are primary long-term sources of environmental contamination.

➤ Control measures

• Prevention and strict enforcement of safety procedures are the best defences because many radiation injuries are not curable.
• Ensure containment and leak prevention at nuclear facilities; routine inspection and maintenance of equipment and storage.
• Safe handling, transport and disposal of radioactive waste and low-level wastes in engineered repositories.
• Frequent monitoring (environmental sampling and quantitative analysis) and emergency preparedness for nuclear accidents.
• Control and prohibition of nuclear weapons tests and use of nuclear weapons to avoid fallout.
• Protect workers from occupational exposure by dosimetry, shielding, training and administrative controls.

E-Waste

Electronic waste (E-waste) comprises discarded electrical and electronic equipment including computers, mobile phones, household appliances, audiovisual devices and their peripherals. E-waste contains both valuable materials (metals) and hazardous substances (lead, mercury, cadmium, brominated flame retardants and persistent organic pollutants).

➤ E-waste in India

• According to the Global E-Waste Monitor 2014, India generated about 17 lakh tonnes of e-waste in 2014.
• Among the top ten Indian cities, Mumbai generates the most e-waste, followed by Delhi, Bengaluru, Chennai, Kolkata, Ahmedabad, Hyderabad, Pune, Surat and Nagpur.
• Sixty-five cities account for over 60% of the country's e-waste generation, while ten states generate about 70% of the total.
• Most e-waste in India is recycled in the informal (unorganised) sector, where primitive recovery methods (open burning, acid leaching) expose workers and communities to toxic emissions and lead to environmental contamination.
• Hazards include inhalation of toxic fumes, dermal contact with hazardous substances and exposure to acids used in metal recovery.
• Solutions require proper education, awareness, affordable and scalable technology for formal recycling, and institutional mechanisms to integrate informal units into formal value chains.
• A holistic approach is necessary to create a safe, inclusive and effective e-waste management system covering collection, transport, recycling and disposal.

Final remarks

The prevention and control of environmental pollution-water, soil, noise, radioactive and electronic-require an integrated approach that combines sound scientific monitoring, appropriate technology, regulatory enforcement, public participation and sustainable practices such as reduced consumption, waste minimisation, cleaner production and ecosystem restoration. Early intervention, pollution prevention and public awareness remain more effective and less costly than remediation after damage has occurred.