1. Chapter 9
Pollution in the world
- Pollution is introduction of substances into the environment, causing unpleasant or
damaging effects on people, animals, plants, buildings.
- Occur due to:
 Natural events (Eg. volcanic eruptions, forest fires)
 Mainly from human activities which contribute the largest amount of harmful
substances and pollutants into the environment
- Pollutants found in waste.
 Waste – materials that are useless and no longer wanted
 Waste generated :
– By households (leftover food, unclean and used water)
– By industrial / agricultural activities
- When waste not disposed properly or if there is an excessive amount of waste, pollution
occurs.
- Eg. Farmer uses excessive amount of fertilizers on farms and generate waste as chemicals in
fertilizers not absorbed by the plant. The chemicals washed away by rain into rivers, thus
polluting them.
- All components in physical environment interconnected and one type of pollution can lead
to another.
Eg. Air pollution caused by industrial waste leads to formation of acid rain.
Eg. When fuel burnt in vehicles or factories, gases like sulfur dioxide and nitrogen oxides are
released and these gases mix with water vapor in the atmosphere to form acid rain. When
acid rain falls into rivers, the rivers become polluted, thus causing water pollution.
Air pollution
- Occurs when pollutants like dust and smoke are released into the environment.
- Dust and smoke particles are suspended in the air and sometimes results in daze.
- Dust and smoke can combine with water vapor and toxic gases from factories and form
smog – more serious form of pollution
- Causes
 Natural Cause – Volcanic Eruptions
Large amount of volcanic ash, smoke and gas released during eruptions.
Eg. 1991 eruption of Mount Pinatubo in Philippines released hot volcanic ash and
gases into the air which blocked the sunlight and caused grey skies in the
surrounding region for days.
 Natural Cause – Forest Fire
Occur naturally in times of prolonged hot and dry weather
High temperatures and low rainfall create very dry conditions in forests and result in
risk of vegetation catching fire
Dust and smoke particles produced by forest fire suspended in air and carried by
winds to areas surrounding forest or even nearby countries
 Human Cause – Industries

2. Power stations and manufacturing industries release large amounts of dust and
smoke into the air.
When fossil fuels are burnt, dust and waste released.
Waste includes fine, black, carbon-based smoke particles called soot and poisonous
gases like sulfur dioxide.
 Human Cause – Motor Vehicles
Greatest source of air pollution in urban areas
In many cities, 90% of dust and smoke particles in air emitted from vehicles.
Emissions have harmful gases like carbon monoxide and nitrogen oxides.
 Human Cause – Construction Work
Clearing of land, construction of buildings and transportation of construction
materials pollute air with dust and smoke particles.
Particles transported by wind to nearby residential areas.
- Extent
Air pollutants – dust , smoke , harmful gas carried by wind from source to other
parts of country, across international boundaries to other countries
Eg. Hazy skies every year but esp. bad in 1997 due to smoke particles from burning
forests in Indonesia carried by wind to Singapore, Malaysia, Brunei, and SEA regions.
 Health Problems
Dust and smoke can cause difficulty in breathing and irritation to people’s throats
and eyes.
When exposed to dust and smoke for long time, we develop respiratory problems.
(Eg. Bronchitis and asthma)
When city experience prolonged smog, toxic gases like carbon monoxide cause
serious health problems and even death.
Sulfur dioxide and nitrogen oxides found in smoke attack person’s respiratory
system, increasing risk of developing lung and heart diseases, even cancer.
Lifespan of people in cities shortened by average of 1 or 2 years.
 Traffic Hazards
High amounts of dust and smoke in air make it difficult for us to see distant objects.
When country experience haze, airports may have to stop all flights until visibility
improves.
Poses as inconvenience and may be dangerous for those driving vehicles.
 Environmental Problems
In some cities, acid rain causes air pollution, destroys forests, kills fish in rivers and
lakes, and corrodes buildings.
Acid rain – common problem in places with large no. of heavy industries
Eg. Chemical industries release large amount of sulfur dioxide and nitrogen oxides
into air as chemicals being processed. The chemicals mix with water vapor in air and
form acid rain.
Water Pollution
- Occurs when pollutants discharged directly into water bodies like rivers, lakes and seas /
pollutants on land blown by wind or washed by rain into water bodies

3. - Some pollutants are poisonous and may remain in water for long time – affect health of
animals that live in water and people who consume the water
- Causes
 Improper disposal of sewage
Sewage – solid or liquid waste produced by households or industries
When sewage not treated before released into rivers or lakes, water bodies get
polluted as sewage contain human waste, detergent and chemicals.
Industrial waste –or waste produced by industries in manufacturing stage esp.
harmful and contain large amount of toxic chemicals.
Waste is sometimes illegally disposed into rivers and seas, causing heavy pollution.
In some countries, sewage is treated at sewage treatment plants to remove waste
products from water and release it back to water bodies. However, some substances
in sewage like detergent are non-biodegradable and cannot be easily broken down
into harmless substance. The substances remain in water and cause pollution.
 Oil Spills
Occur when hull of oil tanker torn by shark rocks or tanker collides with another
ship causing oil it is carrying to spill into the sea
Very difficult to clean up as oil spills spread over large areas and not easily broken
down
- Extent
Water pollution triggers chain reaction in environment and have serious
consequences on all living things.
 Endangering plant and animal species
Oil spill endanger lives of animals.
Oil spill is a layer of oil spreading over water surface.
When animals like sea bird or sea mammals in contact with polluted water, oil sticks
to their feathers and fur.
This removes air trapped in feathers and fur which is a layer of insulation for animals,
causing them to freeze to death in cold.
Oil clogs bird’s feathers and prevents them from flying or floating on the water,
causing them to drown.
Improper disposal of household waste into river destroy aquatic life.
Eg. Household detergent in laundry water get into river and chemicals encourage
algae growth on water surface. Sunlight prevented from reaching plants beneath
and they die as photosynthesis cannot occur.
Animals depend on plants for food will be affected.
 Negative Impact On Human Health
Poison in industrial waste accumulates in bodies of fish and shellfish and passed on
to us when we consume contaminated animals.
People may suffer from cholera and typhoid when they drink contaminated water.
 Economic Loss
Oil spill threaten fisherman livelihood and fishing industry.
When spilled oil reach tourist resort along coast, dirties beach and makes it
unattractive to tourists.

4. Cleaning up oil spill require huge effort and very costly.
Oil spill spread over large area and not easily broken down.
Land Pollution
- Occurs when waste not disposed of properly or chemicals used excessively on farms
- Land population very serious and great concern of many countries.
Eg. USA spends more than US$1 billion per year to clean up litter and waste in illegal dumps.
- Causes
 Improper disposal of waste
Increase in world population and more consumption of goods and services.
More waste produced and countries have difficulty finding places to dispose waste.
Some countries insufficient control over proper disposal of waste and great heaps of
rubbish left in public places or at illegal dumping grounds.
Improper disposal of waste also occur at mining sites.
Waste materials left behind on land after minerals mined or extracted.
 Excessive use of chemical fertilizers
Farmers use chemical fertilizers and pesticides on farm to improve farm fertility and
kill or drive away pests that eat crops or spread diseases
Land polluted when chemicals washed into soil.
Pest develops resistance to pesticides over time and farmers forced to increase
usage of pesticides, worsening soil contamination.
- Extent
 Negative Impact On Human Health
Eyesore and waste not properly disposed is unhygienic and dangerous to human
beings.
Waste attracts pests like flies and rats that carry germs and spread diseases.
Farmers exposed to large amount of pesticides risk developing cancer and liver
failure.
 Poisoning of animals
Pesticides used on farm affect pest and useful organism like earthworms that
fertilize soil.
Earthworm eaten by birds, toxic chemicals stored in bodies passed on to birds and
affect reproductive systems. Birds may lay eggs with thin, fragile shells that break
easily and kill nestlings inside. This may eventually lead of extinction of certain
species of birds.
Measures taken to reduce pollution
- Problem cannot be wiped out completely and likely to increase as population and industries
grow.
- Measures adopted to prevent pollution getting out of control.
- International efforts
 Pollutants carried by wind or water from one country to next – regional problem
 Governments from various countries and international organizations (Eg. United Nations
Environment Programme UNEP) work closely together to reduce pollution.

5.  Only through cooperation with one another, we can manage pollution problem
effectively.
 Eg. United Nations organized Earth Summit in 1992 and 2002 for world leaders to meet
and discuss strategies to protect environment.
World leaders commit themselves to sustainable development – development that
meets the needs of present generations without compromising ability of future
generations to meet their own needs.
Some commitments made at 2002 Summit were to manage toxic chemicals, increase
access to clean water supply and proper sewage systems.
 Eg. SEA region, Singapore work with Indonesia and Malaysia to prevent pollution in
Malacca and Singapore Straits.
Countries implement mandatory ship reporting system which require all ships
passing through to report and provide info on any damage or defects they may have.
Ships also have to report any pollutants released from their vessel.
This ensures that relevant authorities are aware of what being discharged into the
waters.
Authorities from 3 countries also trained to respond quickly to any incidents of oil
spill.
- National efforts
 Government protect environment with these ways.
 Enforcing laws and regulations
Many countries enforce laws to control amount of pollutants emitted by industries
and ensure companies treat their waste before disposing them.
In SG, National Environment Agency (NEA) carries out programmes to monitor,
reduce and prevent air, water and land pollution.
Eg. All industries, power stations and vehicles in SG need to ensure pollutants
produced are within safety limits.
 Using alternative sources of energy
Government of some countries tries to reduce pollution by decreasing no. of
pollutants released into environment.
Use alternative sources of “clean” energy that does not release harmful materials
into environment.
Eg. Wind energy, hydroelectricity, solar energy.
 Using advanced technology
Treat waste and remove pollutants to reduce impact of pollution on environment.
Eg. Government in developed countries invests in building sewage treatment plants
to treat waste before it is released into water bodies.
 Developing proper waste disposal methods
Important to manage waste properly and not cause pollution
Landfill
 Huge pits dug in the ground to dispose solid waste.
 Waste dumped into pits and covered with layer of soil.
 Left to rot or decompose underground.
 Takes up a lot of space – When one landfill used up, another pit created.

6. Incineration
 Incinerate and burn waste at high temperature.
 Reduce volume of waste by 90%.
 Energy produced from incineration converted to electricity.
 Releases dust particles into air – air pollution
 Some waste like concrete cannot be burnt completely.
 Educating the public
Encourage people and industries to produce less waste
Public education programmes like campaigns, talks inform people about harmful
effects of excessive waste on environment.
Citizens given suggestion to reduce land pollution through 3Rs – reduce, reuse,
recycle
Noise pollution
- Occurs when unwanted sounds are added to the environment.
- As cities develop and more activities are carried out, a lot of noise generated from vehicles,
industrial activities, household gadgets and loud music.
- Annoying noise can affect quality of life.
- Causes
 Traffic
Common cause esp. in cities
Cars / other types of vehicles on busy road – 60 to 90 decibels
Aircraft taking off – 120 decibels
MRT entering tunnel – 90 decibels
 Construction and other human activities
Noise from drilling, piling, knocking, use of heavy machinery.
People talking loudly, events like concerts.
- Extent
 Unpleasant fact of life and affect quality of life.
 Causes discomfort and negative impact on health.
 Long-term exposure to noise pollution can :
damage hearing or cause loss of hearing
increase heart rate, anxiety, stress level that lead to related health problems like
high blood pressure
lead to poor performance in school , at work as ability to concentrate affected
- Measures
 National
Enforcing laws and regulations
Government of country set limits on acceptable noise level produced by vehicles,
workplaces, industries and construction sites.
In SG, NEA and police set limits and deal with noise in residential areas if it becomes
a public nuisance.
Noise reduction Methods

7. SG and many countries construct sound barriers like tall wooden fences along busy
roads to reduce level of noise transmitted to nearby housing areas.
Trees and shrubs planted also.
Walls of building covered with sound-proof material to reduce any noise produced
by heavy machinery outside.
Device called muffler installed on noisy equipment or engines of vehicles to absorb
noise produced.