Pollution, and Global Environmental Issues
Pollution and Global Environmental Issues
Air Pollution – Causes, Effects and Prevention
Air & water pollutions – Cusses, effects and prevention starts with understanding what air pollution is.
Air pollution is the presence of harmful substances in the air that upset the natural balance of the atmosphere.
| Source / Pollutant | Main causes (simple classroom view) | Important effects |
|---|---|---|
| Vehicle exhaust | Burning petrol and diesel in cars, buses, lorries, two-wheelers. | Releases carbon monoxide, nitrogen oxides, tiny particles → breathing problems, smog in cities. |
| Industrial smoke | Factories, power plants, brick kilns burning coal and furnace oil. | Air looks hazy, causes respiratory diseases, contributes to acid rain and climate issues. |
| Burning of biomass | Burning wood, crop residues, garbage. | Indoor and outdoor air becomes smoky → eye irritation, lung damage. |
| Household activities | Use of kerosene stoves, chulhas without proper ventilation, use of chemicals and sprays. | Indoor air pollution; higher risk for women, children and aged persons. |
Effects of air pollution
- Breathing problems – asthma, coughing, allergies.
- Reduces visibility, causes smog in big cities.
- Damages leaves of plants, reduces crop yield.
- Contributes to global environmental issues like global warming and acid rains.
Prevention and control of air pollution
| Measure | How it helps |
|---|---|
| Use of public transport, car-pooling | Reduces number of vehicles on road → less exhaust gases. |
| Planting trees in schools and communities | Trees absorb carbon dioxide and give oxygen; act as “green filters”. |
| Use of cleaner fuels | LPG, CNG, electricity produce fewer pollutants than coal and kerosene. |
| Maintaining vehicles properly | Regular servicing reduces smoke and saves fuel. |
Memory Line: “Air pollution = dirty air from vehicles, industries and burning → harms lungs, plants and climate.”
Exam Tip: When a question asks about “causes, effects and prevention”, always write at least one point from each side: source, health / environment effect, and simple control measure.
Water Pollution, Sewage and Treatment of Polluted Water
Air & water pollutions – Cusses, effects and prevention, Water, Sewage, Treatment of polluted water are linked in environmental science.
Water pollution is the contamination of water bodies like rivers, ponds, lakes and groundwater with substances that make it unsafe for drinking, bathing, irrigation and aquatic life.
| Cause of water pollution | Simple examples | Key effects |
|---|---|---|
| Domestic sewage | Kitchen waste, soaps, detergents, human excreta entering drains. | Spread of diseases, foul smell, reduces oxygen for fish. |
| Industrial effluents | Chemical waste, dye water, hot water from factories. | Poisonous to fish, changes colour and temperature of water. |
| Agricultural run-off | Fertilisers and pesticides washed from fields into canals and rivers. | Algal blooms, fish kills, long-term health effects on humans. |
| Oil spills and plastics | Leakage of oil, plastic bags and bottles thrown into water. | Blocks sunlight and oxygen, harms aquatic plants and animals. |
Sewage and its treatment
- Sewage is the wastewater from homes, schools, hospitals, markets and small industries that contains organic matter, soaps, oils and germs.
- Untreated sewage entering rivers is a major cause of water pollution.
| Stage in sewage treatment (simple) | What happens |
|---|---|
| Physical (primary) treatment | Screening and sedimentation remove large objects (plastics, cloth, sand). |
| Biological (secondary) treatment | Microorganisms decompose organic matter in aeration tanks. |
| Disinfection | Chlorine or other methods used to kill disease-causing germs. |
Prevention of water pollution
- Do not release untreated sewage into water bodies.
- Avoid throwing plastics, garlands, chemicals and oils into ponds and rivers.
- Use toilets connected to safe disposal systems.
- Use fertilisers and pesticides in limited and proper quantity.
Memory Line: “Water pollution = dirty water from sewage and chemicals → treat before release, never use rivers as drains.”
Exam Tip: In short answers, always link sewage with wastewater from homes and treatment with physical + biological + disinfection steps.
Better Housekeeping Practices, Sanitation and Disease
Better housekeeping practices, Sanitation and Disease show how cleanliness in daily life reduces pollution and illness.
Better housekeeping practices
- Storing food in covered containers to avoid contamination by flies and dust.
- Segregating dry and wet waste at home and school.
- Proper disposal of solid waste instead of throwing it into streets or drains.
- Regular cleaning of bathrooms, toilets, wash areas and water storage tanks.
Sanitation and Disease
Sanitation means proper disposal of human excreta, sewage and solid waste to maintain hygienic conditions.
| Poor sanitation condition | How disease spreads | Example diseases |
|---|---|---|
| Open defecation | Human excreta carried by rainwater into ponds and wells; germs spread easily. | Diarrhoea, cholera, typhoid. |
| Stagnant sewage and water | Acts as breeding place for mosquitoes and flies. | Malaria, dengue (mosquito-borne); other infections spread by houseflies. |
| Uncovered drains and garbage heaps | Attracts rodents, insects and dogs; bad smell and germs are spread. | Skin infections, stomach infections, worm infestations. |
Improving sanitation and health
- Use of safe toilets and proper hand-washing with soap before eating and after using toilets.
- Keeping surroundings clean – “no stagnant water, no open garbage heaps”.
- Community participation in cleaning streets, school premises and public places.
Memory Line: “Good sanitation breaks the chain: fewer germs → fewer diseases.”
Exam Tip: When a question combines “sanitation and disease”, always connect open defecation + unsafe water with diarrhoeal diseases and stagnant water with mosquito-borne diseases.
Alternative Arrangement for Sewage Disposal
Alternative arrangement for sewage disposal is important for villages, slums and areas where underground sewage systems are not available.
| Alternative method | Basic idea (simple level) | Benefits |
|---|---|---|
| Septic tank system | Closed underground tank where sewage is stored; solids settle and are decomposed by bacteria; liquid flows to soak pits. | Useful for houses and small buildings; does not require central sewage pipes. |
| Single pit / twin pit latrines | Excreta collected in pits; allowed to decompose and later used as manure. | Low cost, suitable for rural areas; reduces open defecation. |
| Eco-friendly toilets | Use very little water or separate solid and liquid waste. | Saves water and avoids direct contamination of water sources. |
| Community toilets with safe disposal | Shared facilities with proper cleaning and connection to septic tanks or sewage lines. | Helpful in crowded urban and semi-urban areas. |
- Alternative systems reduce pollution of ponds, tanks and rivers.
- They support public health when designed and maintained properly.
Memory Line: “Where underground sewage is absent, septic tanks and pit latrines act as alternative safe disposal systems.”
Exam Tip: If a question asks for “alternative arrangement for sewage disposal”, name septic tank and twin pit latrines with one clear point of how each works.
Global Environmental Issues – Greenhouse Effect & Global Warming
Global Environmental Issues – Greenhouse effect, Global warming belong to world-level environmental problems.
Greenhouse effect – natural and enhanced
- Earth’s atmosphere contains gases like carbon dioxide, methane, water vapour and ozone.
- These gases trap some of the heat from the Sun and keep Earth warm enough for life – this is the natural greenhouse effect.
- When human activities increase these gases beyond normal levels, more heat is trapped – this is enhanced greenhouse effect.
| Greenhouse gas | Main human sources |
|---|---|
| Carbon dioxide (CO₂) | Burning of fossil fuels (coal, petrol, diesel), deforestation. |
| Methane (CH₄) | Rice fields, cattle, landfill sites, leakage from gas pipelines. |
| Water vapour | Evaporation, power plants and many natural processes. |
Global warming
- Global warming is the gradual increase in average temperature of Earth’s atmosphere due to enhanced greenhouse effect.
- It leads to melting of ice caps, rise in sea level, changes in rainfall patterns and more extreme weather events.
| Aspect | Simple classroom explanation |
|---|---|
| Cause | Increased greenhouse gases from industries, vehicles, burning of fuels, deforestation. |
| Main impacts | Higher temperatures, changing monsoon, threats to biodiversity and agriculture. |
| Control measures | Energy conservation, tree planting, use of renewable energy, reduced use of fossil fuels. |
Memory Line: “Greenhouse effect is natural and needed; too many greenhouse gases cause global warming.”
Exam Tip: Do not write “greenhouse effect is bad”. Write: natural greenhouse effect is useful; enhanced greenhouse effect leads to problems like global warming.
Global Environmental Issues – Ozone Depletion & Acid Rains
Global Environmental Issues – Ozone depletion, Acid rains are also world-level concerns.
Ozone layer depletion
- Ozone (O₃) in the upper atmosphere (stratosphere) forms a layer that absorbs harmful ultraviolet (UV) rays from the Sun.
- Certain man-made chemicals (for example, chlorofluorocarbons used earlier in refrigerators and sprays) can damage this ozone layer.
- Thinning of this layer is called ozone depletion.
| Aspect | Key points |
|---|---|
| Cause | Release of ozone-depleting substances like CFCs into the atmosphere. |
| Effect | More UV rays reach Earth’s surface, increasing risk of skin problems and affecting plants and plankton. |
| Control | Gradual phasing out of CFCs, using ozone-friendly products. |
Acid rains
- When gases like sulphur dioxide and nitrogen oxides mix with air moisture, they form acids.
- Rainfall containing these acids is called acid rain.
| Source | Effect |
|---|---|
| Coal-based power plants, industrial chimneys, vehicle exhaust | Release sulphur dioxide and nitrogen oxides into the air. |
| Acidic rainwater | Damages leaves of plants, makes lakes and ponds too acidic for fish, corrodes buildings and monuments. |
- Control measures include use of cleaner fuels, pollution control equipment and strict emission standards.
Memory Line: “Ozone layer protects from UV; acid rain damages plants, water bodies and buildings.”
Exam Tip: For questions on ozone depletion, always mention “less UV protection”; for acid rain, mention “damage to plants, aquatic life and monuments”.
Nitrogen Cycle
Nitrogen cycle is one of the important Global Environmental Issues topics in Life Processes because it shows how a key element moves through nature.
Nitrogen is needed for proteins and nucleic acids in plants and animals, but most nitrogen is present in the air as N₂ gas, which cannot be used directly by plants.
Main stages of the nitrogen cycle (simple classroom view)
| Stage | What happens |
|---|---|
| Nitrogen fixation | N₂ gas from the air is converted into usable compounds like nitrates and ammonium by lightning, certain bacteria in soil and roots of legumes, and by industrial processes (fertilisers). |
| Uptake by plants | Plants absorb nitrates from the soil and use them to build proteins. |
| Transfer to animals | Animals obtain nitrogen by eating plant parts or other animals. |
| Decomposition | When plants and animals die, decomposers break down their bodies and release nitrogen compounds back to the soil. |
| Denitrification | Certain bacteria convert nitrates back into N₂ gas, returning it to the atmosphere. |
- The nitrogen cycle keeps the amount of nitrogen in the atmosphere and soil balanced.
- Overuse of nitrogen fertilisers can disturb this balance and cause water pollution.
Memory Line: “Nitrogen cycle = air → soil → plants → animals → back to air through bacteria and decomposers.”
Exam Tip: When drawing or explaining the nitrogen cycle, always show nitrogen fixation, plant uptake, animal use, decomposition and return to atmosphere. Missing any of these steps can lose marks.