Pollution is an undesirable change in the chemical, physical or biological characteristics of the natural environment. The environment is polluted with harmful substances or pollutants.

Pollutant is any substance that is present in an excessive amount in the environment as a result of human activities. It has damaging effects on living organism.

Pollutants may be toxic substances such as pesticides or natural constituents of the atmosphere, such as carbon dioxide. They may affect the soil, rivers, seas or the atmosphere.

There are four types of pollution:

Water pollution

Thermal pollution

Noise pollution

Air pollution

Types of

pollutions

1. AIR POLLUTION Air pollution occurs when pollutants such as smoke, dirt, dust

and poisonous gases are released into the air endangering human lives and other living organisms.

Most air pollutants come from burning of fossil fuels from motor vehicles.

Examples of air pollutants are carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxide (NO) and sulphur dioxide (SO2).

Pollutant Sources EffectsCarbon monoxide (CO) Odourless, colourless

and toxic gas.

Incomplete combustion of fossil fuels.

Combustion sources such as motor vehicle exhaust, smoke from fires, engine fumes.

Health Combines with haemoglobin to form

carboxyhaemoglobin which reduces the ability of the blood to transport oxygen.

Early symptoms of carbon monoxide poisoning are headaches, nausea and fatigue.

Prolonged exposure can lead to brain damage and even death.

Carbon dioxide (CO2) Odourless,

colourless gas.

Combustion of fossil fuels.

Health Causes emphysema. Affects respiration.Building Contributes to acid rain which damages buildings.Climate Contributes to greenhouse effect and global

warming.Nitrogen monoxide (NO) and nitrogen dioxide(NO2) NO-odourless,

colourless gas. NO2-browmish gas

Combustion of fossil fuels.

Motor vehicle exhaust

Health Damages lung tissues. May cause bronchitis. Irritates the eyes. Lowers the body’s defence against flu.Agriculture Contributes to acid rain which reduces the pH of

soil, lakes and rivers.Building Contributes to acid rain which destroys buildings.Climate Contributes to acid rain.

Sulphur dioxide (SO2) Colourless, pungent

and acidic gas.

Combustion of fossil fuels which contain sulphur.

Health Irritates and damages the lining of the eyes, air

passages and lungs.

Dissolves in water. Industries. Causes coughing and wheezing. Combines with rainwater to form acid rain that may

cause skin diseases.Agriculture Reduces the growth of plants. Damages the leaves and may kill the plants. Contributes to acid rain which lowers the pH of soil,

lakes and rivers.Buildings Contributes to acid rain which corrodes iron, copper,

steel, aluminium and stonework, thereby destroying buildings.

Climate Causes acid rain.

Fine particular matter. (Includes smoke, fumes, dust, ash and pollen) Tiny and invisible The composition of

particulate matter varies with place, season and whether conditions.

Combustion of fossil fuels from motor vehicles, agricultural burning and industries.

Forest fire Quarries and asbestos

factories

Health Irritates the eyes and respiratory tract. Contributes to haze which can cause asthma attack,

conjunctivitis, sore throat, bronchitis and reduced visibility.

Agriculture Deposits on leaves and darkens vegetation. Blocks stomata, thus lowering the rate of

photosynthesis. The crop yield is reduced.Buildings Soot can darken building.Climate Contributes to formation of haze and smog which

can reduce light intensity.Lead Combustion of fossil

fuelsHealth Reduces the sensitivity of the hands and feet

coordination. Retards mental development in children. Disrupts body’s ability to produce new cell.

Hydrocarbon Combustion of fossil fuels from motor vehicles

Health Affects growth Causes cancer

Other than that, air pollution also causes acid rains. Acid rain only occurs when the pH of the rain is less than

5.0(natural rain water has a pH of about 5.4)

Combustion of fossil fuels releases sulphur dioxide and oxides of nitrogen which contribute to acid rain.

Sulphur dioxide and oxides of nitrogen form acidic solutions when dissolves in water.

Sulphur dioxide combines with water vapour to form sulphuric acid.

2SO2(g) + O2(g) + 2H2O(l) 2H2SO4(aq)

Oxides of nitrogen combine with water vapour to form nitric acid.

Then, these acid will fall back as acid rain. Carbon dioxide in the air also contributes to acid rain. It

dissolves in water to form carbonic acid. The effect of acid rain is shown below:

Increases the acidity of aquatic

ecosystems leading to the killing of planktons and

aquatic organism

Leaching of minerals from the

soil such as calcium, causing

infertile soil

Releases ions of heavy metals such as lead which may

contaminate the water

Reduces the pH value of the soil

making it unsuitable for farming

Destroyed plant tissues and

damages plant roots

Corrodes metals, marble, rubber,

plastics, stonework and other materials

Effects of acid rain

The air quality is measure by Air Pollution Index (API) It is normally includes the major pollutants which could

cause potential harm to human health. In Malaysia, the air pollutants included are ozone,

carbon monoxide, nitrogen dioxide, sulphur dioxide and suspended particulate matter.

This index is calculate by using the concentrations of major air pollutants, but it is developed in easily understood ranges of values as shown below

API Status Level of pollution 0-50 Good Low, no ill effects on health 51-100 Moderate Moderate pollution, no ill effects on health 101-200 Unhealthy Mild aggravation of symptoms among high risk group 201-300 Very unhealthy Significant aggravation of symptoms and decreased exercise

tolerance among high risk groups 301-500 Hazardous Severe aggravation of symptoms and a danger to healthAbove 500 Emergency Severe aggravation of symptoms and a danger to health

This index helps us to take precautionary measures by drinking more water, staying indoors and wearing masks when the air pollution index exceeds 200.

2. Water pollution.

Water pollution occurs when people discharging agriculture wastes, industrial waste, domestic waste and sewage into rivers.

The sources of water pollution and the effects of water pollution are shown below.

Fertilisers and pesticide from

farmsNitrates PhosphatesPesticides Herbicides

Effluent from factories

Heavy metalsChemicalsOil Grease

Sewage effluent

Detergent FaecesNitrates

Oil spillsGreaseOil

Non-biodegradable

rubbishSuspended

solidsRubbishOil

Sources and pollutants of

water pollution

Effects of water pollution

Human healthUntreated water contains pathogen such as Vibrio bacteria which causes cholera.Pesticides and herbicides passed to humans through the food chain are harmful.Heavy metals such as mercury cause nervous disorders, blindness, paralysis and even death

Animals and plants Excess nitrates and phosphates

lead to eutrophication.Rubbish and oil reduce light

penetration and diffusion of oxygen into water. Aquatic organisms may die due to lack of light and oxygen.

Oil covers the gills of fishes affecting their respiration.

Decomposition of decayed materials by saprophytic bacteria reduces the oxygen content in the water

Eutrophication is a natural process whereby an aquatic ecosystem becomes enriched with nutrients causing an excessive growth of aquatic plants

EutrophicationEutrophication

Excess of the organic and inorganic wastes that enter a river or a lake enrich the water

with nutrients

Photosynthesizing organisms particularly algae that grow rapidly, result in population

explosion known as algal bloom

High diversity of algae reduces the light intensity hence lead to the death of other

photosynthetic organisms

The decomposition of these dead organisms by aerobic bacteria causes severe depletion

of water dissolved oxygen,

Eutrophication

Eutrophication

The aerobic bacteria use-up oxygen faster then it replenished; BOD increase

Causing the deathof other aerobic organisms such as fish, prawns etc.

Nutrients can come from many sources such asa. Fertiliser(especially nitrates and phosphate)

from agriculture fieldsb. Sewage treatment plant dischargesc. Run-off of animal waste

The increased nutrients promote rapid growth of algae when they are deposited in rivers, lakes and streams.

This excessive growth of algae is often called an algae bloom

Algae blooms endanger the ecosystem in two main ways. 1.The densely populated algae cover the water surface and

block sunglight. Unable to carry out photosynthesis, the aquatic plants die.

When these plants die, aquatic animals lose their food sources and habitats. As a result, the food chains and ecosystem change.

Algae also reduce the level of dissolved oxygen in the water. 2. When the algae die, decomposing organisms especially

saprophytic bacteria use up oxygen for its activities This reduces the oxygen content in the water.

A depletion in oxygen results in an increases in biochemical oxygen demand (BOD)

Eutrophication increases the BOD value in the water.

BOD refers to the amount of oxygen utilised by microorganisms to oxidise all organic matter in one litre of water

The higher the BOD value, the more polluted the water as the dissolved oxygen level decreases.

3. Thermal Pollution

Thermal pollution is the degradation of water quality by any process that changes ambient water temperature.

A common cause of thermal pollution is the use of water as a coolant by power plants and industrial manufacturers. When water used as a coolant is returned to the natural environment at a higher temperature, the change in temperature (a) decreases oxygen supply, and (b) affects ecosystem composition. Urban runoff--stormwater discharged to surface waters from roads and parking lots--can also be a source of elevated water temperatures.

When a power plant first opens or shuts down for repair or other causes, fish and other organisms adapted to particular temperature range can be killed by the abrupt rise in water temperature known as 'thermal shock'.

An increase in temperature of water will cause the following:

a) It reduces the level of dissolved oxygen in water. This affects the life of aerobic aquatic organisms

b) It causes some aquatic organisms to die because they only survive at suitable temperatures. Some organisms also move away. This affects the food chain and also the entire ecosystem.

c) It encourages some algae to grow rapidly which can lead to a higher BOD value.

4. Noise Pollution

Noise pollution disturbs our health and behavior in a number of ways including deafness causing lack of sleep, irritability, indigestion, heartburn, high blood pressure, ulcers, and heart disease. Just one noise explosion from a passing truck drastically alters ourendocrinal, neurological, and cardiovascular functions in many individuals. If this is prolonged or frequent, the physiological disturbances become chronic and contribute to mental illness.

Sometimes, even low levels of noise are irritating and can be frustrating, and high volumes can be annoying. Natural sounds are less irritating than those we find uncontrollable but intermittent sounds such as a tap dripping water can be more irritating than the sound of falling rain.

Noise more than 50dB can be very difficult to hear and interpret and cause problems such as partial deafness.

Increased nose levels gives rise to al ack of concentration and accuracy at work, and reduce one’s productivity and performance. Difficult tasks can be impaired, and instructions or warnings difficult to be.

Noise more than 50dB can be very difficult to hear andinterpret and cause problems such as partial deafness.

Increased noise levels gives rise to a lack ofconcentration and accuracy at work, and reduce one’sproductivity and performance. Difficult tasks can be heard and interpreted, causing accidents.