We know that we can survive for some time
without food, but we cannot survive even for
a few minutes without air.
This simple fact tells us how air
is very important for us.
You already know that air
consist of a mixture of gases. By
volume, about 78% of this
mixture is nitrogen and about
21%is oxygen. Carbon dioxide,
argon, methane, ozone and
water vapour are also present in
very small quantities.
Do you know where the smoke could
have come from?
Addition of such substances to the atmosphere
modifies it. When air is contaminated by unwanted
substance which have a harmful effect on both the
living and the non-living, it is referred to as
The Gaseous Composition of Unpolluted Air
The Gases Parts per million (vol)
Carbon Dioxide 305
Nitrous oxide 0.49
Organic vapours ca.0.02
How does Air Get Polluted?
The substance which contaminate the air
are called air pollutants. Sometimes,
such substances may come from natural
sources like smoke and dust arising from
forest fires or volcanic eruptions.
Pollutants are also added to the
atmosphere by certain human activities.
The sources of air pollutants are
factories, power plants, automobile
exhausts and burning of firewood and
Do you know?
Vehicles produce high levels of pollutants like
carbon monoxide, carbon dioxide, nitrogen
oxides and smoke. Carbon monoxide is
produced from incomplete burning of fuels such
as petrol and diesel. It is a poisonous gas. It
reduces the oxygen-carrying capacity of the
If the vehicles registered in Delhi are lined up
one after the other, the total length would be
nearly equal to the combined lengths of the two
longest rivers in the world, Nile and Amazon.
Many industries are also
responsible for causing air pollution.
Petroleum refineries are a major
source of gaseous pollutants like
sulphur dioxide and nitrogen
dioxide. Sulphur dioxide is produced
by combustion of fuels like coal in
power plants. It can cause
respiratory problems, including
permanent lung damage.
Indoor air pollution
It refers to the physical, chemical, and biological
characteristics of air in the indoor environment within a
home, building, or an institution or commercial facility.
Indoor air pollution is a concern in the developed
countries, where energy efficiency improvements
sometimes make houses relatively airtight, reducing
ventilation and raising pollutant levels. Indoor air
problems can be subtle and do not always produce
easily recognized impacts on health. Different
conditions are responsible for indoor air pollution in
the rural areas and the urban areas.
In the developing countries, it is the rural areas that
face the greatest threat from indoor pollution, where
some 3.5 billion people continue to rely on traditional
fuels such as firewood, charcoal, and cowdung for
cooking and heating. Concentrations of indoor
pollutants in households that burn traditional fuels are
alarming. Burning such fuels produces large amount
of smoke and other air pollutants in the confined
space of the home, resulting in high exposure. Women
and children are the groups most vulnerable as they
spend more time indoors and are exposed to the
smoke. In 1992, the World Bank designated indoor air
pollution in the developing countries as one of the four
most critical global environmental problems.
Daily averages of pollutant level emitted
indoors often exceed current WHO
guidelines and acceptable levels.
Although many hundreds of separate
chemical agents have been identified in
the smoke from biofuels, the four most
serious pollutants are particulates, carbon
monoxide, polycyclic organic matter, and
formaldehyde. Unfortunately, little
monitoring has been done in rural and
poor urban indoor environments in a
manner that is statistically rigorous.
In urban areas, exposure to indoor air
pollution has increased due to a variety of
reasons, including the construction of more
tightly sealed buildings, reduced ventilation,
the use of synthetic materials for building
and furnishing and the use of chemical
products, pesticides, and household care
products. Indoor air pollution can begin
within the building or be drawn in from
outdoors. Other than nitrogen dioxide,
carbon monoxide, and lead, there are a
number of other pollutants that affect the air
quality in an enclosed space.
Volatile organic compounds originate mainly
from solvents and chemicals. The main indoor
sources are perfumes, hair sprays, furniture
polish, glues, air fresheners, moth repellents,
wood preservatives, and many other products
used in the house. The main health effect is the
imitation of the eye, nose and throat. In more
severe cases there may be headaches, nausea
and loss of coordination. In the long term, some of
the pollutants are suspected to damage to the liver
and other parts of the body.
Tobacco smoke generates a wide range of harmful
chemicals and is known to cause cancer. It is well
known that passive smoking causes a wide range
of problems to the passive smoker (the person
who is in the same room with a smoker and is not
himself/herself a smoker) ranging from burning
eyes, nose, and throat irritation to cancer,
bronchitis, severe asthma, and a decrease in lung
Pesticides , if used carefully
and the manufacturers,
instructions followed carefully
they do not cause too much
harm to the indoor air.
Biological pollutants include pollen
from plants, mite, hair from pets, fungi,
parasites, and some bacteria. Most of
them are allergens and can cause
asthma, hay fever, and other allergic
Formaldehyde is a gas that
comes mainly from carpets, particle
boards, and insulation foam. It
causes irritation to the eyes and
nose and may cause allergies in
Asbestos is mainly a
concern because it is
suspected to cause
Radon is a gas that is emitted
naturally by the soil. Due to
modern houses having poor
ventilation, it is confined inside
the house causing harm to the
Another effect of air pollution is acid rain. The
phenomenon occurs when sulphur dioxide and
nitrogen oxides from the burning of fossil fuels
such as, petrol, diesel, and coal combine with
water vapour in the atmosphere and fall as rain,
snow or fog. These gases can also be emitted
from natural sources like volcanoes. Acid rain
causes extensive damage to water, forest, soil
resources and even human health.
Many lakes and streams have been contaminated and
this has led to the disappearance of some species of
fish in Europe, USA and Canada as also extensive
damage to forests and other forms of life. It is said that
it can corrode buildings and be hazardous to human
health. Because the contaminants are carried long
distances, the sources of acid rain are difficult to
pinpoint and hence difficult to control. For example,
the acid rain that may have damaged some forest in
Canada could have originated in the industrial areas
of USA. In fact, this has created disagreements
between Canada and the United States and among
European countries over the causes of and solutions
to the problem of acid rain. The international scope of
the problem has led to the signing of international
agreements on the limitation of sulphur and nitrogen
Chlorofluorocarbons are other kinds
of pollutants which are used in
refrigerators, air conditioners and
aerosol sprays. CFCs damage the
ozone layer of the atmosphere i.e.
ozone layer protect us from harmful
ultraviolet rays of the sun.
Automobiles burn diesel and petrol,
also produce tiny particles which
remain suspended in air for long
periods. They reduce visibility. When
inhaled , they cause diseases. Such
particles are also produced during
industrial processes like steel making
and mining. Power plants give out
tiny ash particles which also pollute
The Taj Mahal
also get affected from pollution
Taj Mahal located in Agra has
become a matter of concern. Experts
have warned that pollutants in air are
discoloring its white marble. So, it is
not only living organisms that get
affected by polluted air but non-living
things like buildings, monuments and
statues also get affected.
A part of the radiation that falls on the earth is
absorbed by sun’s rays and a part is reflection
back into space. A part of the reflected radiation
is trapped by the atmosphere. The trapped
radiations further warm the earth. The trapped
heat warms the green house. The trapping of
radiations by the earth’s atmosphere is similar.
That is why it is called the greenhouse effect.
Without this process, life would not have been
possible on the earth. But now it threatens life.
CO2 is one of the gases responsible for this effect.
A Serious Threat!
Global warming can cause sea levels to rise
dramatically. In many places, coastal areas have
already been flooded. Global warming could result in
wide ranging effects gases at the present level.
Otherwise, the temperature may rise by more than 2
degrees Celsius by on rainfall patterns, agriculture,
forests, plants and animals. Majority of people living in
regions which are threatened by global warming are in
Asia. A recent climate change report gives us only a
limited time to keep the greenhouse the end of the
century, a level considered dangerous.
What can we done to reduce air
There are many success stories in our fight
against air pollution. For example, a few years ago,
Delhi was one of the most polluted cities in the
world. It was being choked by fumes released from
automobiles running on diesel and petrol. A
decision was taken to switch to fuels like CNG and
unleaded petrol. These measures have resulted in
cleaner air for the city.
There is a need to switch over to alternative fuels
instead of the fossil fuels for our energy
requirements. These could be solar energy,
hydropower and wind energy.
Water becomes “dirty” when we use it for
washing clothes, bathing, etc. This means that
we art adding some materials to the water,
which spoil its quality and changes its smell and
Whenever harmful substances such as sewage,
toxic chemicals, silt, etc., get mixed with water
becomes polluted. The substances that pollute
water are called water pollutants.
How does Water Get
Ganga is one of the most famous rivers of the India. It
sustains most of the northern, central and eastern
Indian population. Millions of people depend on it for
their daily needs and livelihood. However, recently a
study by the World Wide Fund for Nature found that
Ganga is one of the ten most endangered river in the
world. The pollution levels have been rising for many
years. We have reached this stage because the towns
and cities, through which the river flows, throw large
quantities of garbage, untreated sewage, dead bodies,
and many other harmful things, directly into the river.
In fact the pollution levels are so high that aquatic life
This Ganga story tell us how does
Water Get Polluted
Many industries discharge harmful chemicals into
rivers and streams, causing the pollution of
water. Examples are oil refineries, paper
factories, textile and sugar mills and chemical
factories. These industries cause chemical
contamination of water. The chemicals released
include arsenic, lead and fluorides which lead to
toxicity in plants and animals. There are
regulations to prevent this. Industries are
supposed to treat the waste produced before
discharging it into waters, but quite often the
rules are not followed. The soil is also affected by
impure water, causing changes in acidity, growth
of worms, etc.
Sometimes untreated sewage is
thrown directly into river. It
contains food wastes,
detergents, microorganisms, etc.
Water contaminated with
sewage may contain bacteria,
viruses, fungi and parasites
which cause diseases like
cholera, typhoid and jaundice.
Do you know?
Hot water can also be a pollutant!
This is usually water from power
plant and industries. It is released
into the rivers. It raises the
temperature of the waterbody,
adversely affecting the animals
and plants living in it
Water which is suitable for drinking is called
potable water. You have seen how various
physical and chemical processes in the sewage
treatment plants help to clean water before
discharging it into water bodies. Similarly,
municipal bodies treat the water before
supplying it to households.
Do you know?
25% of the world’s population is without safe
How is Water Purified?
• You have already seen how water is filtered. This is a
physical method of removing impurities. A popular
household filter is a candle type filter.
• Many household use boiling as a method for obtaining
safe drinking water. Boiling kills the germs present in
• Chlorination is a commonly used chemical method for
purified water. It is done by adding chlorine tablets or
bleaching powder to the water.
We must be cautions. We should not use more
chlorine tablets than specified.
We can think of creative
ideas like reusing water used
for washing and for other
household tasks. For
example, water used for
washing vegetable may be
used to water plants in the
Pollution is no longer a
distant phenomenon. It is
affecting the quality of our
daily lives. Unless we all
realise our responsibility
and start using
processes, the very survival
of our planet is in danger.
Do you know?
While brushing your teeth,
leaving the tap running
may waste several liters of
water. A tap that drips once
every second wastes a few
thousand liters of water
every year. Think about it!
SLOGANS FOR POLLUTION
1. Be part of the solution, not of air
2. Earth loves you. Love it back.
3. Join the revolution and stop the
4. Enjoy nature. Recycle.
5. I have a dream and it's Green
6. Give our children a Green
7. Nature is life. No nature no life.
8. Forever Green
9. Fresh air and clean water.
10. We created pollution. We have
11. Keep earth green not grey.
Class - viii-c
roll no. - 22