Sources, Effects And Measures To Control
Air pollution is an increasingly important environmental issue in urban areas. The rapid growth of motor
vehicles along with the industrial development contributes to a definite air pollution pattern with clear
trends of deteriorated air quality. Air pollution is basically the presence of foreign substances in the Air. Few
specific definitions of air pollution are given below:
“Air pollution means the presence in the outdoor atmosphere of one or more contaminants, such as dust,
fumes, gas, mist (tiny droplets of water hanging in the air), odour (smell), smoke or vapour, in quantities,
with characteristics, and of durations such as to be injurious to human, plant or animal life or to property or
which unreasonably interfere with the comfortable enjoyment of life and property”.
Engineers Joint Council (USA)
“Air pollution is the presence in the ambient atmosphere of substances, generally resulting from activity of
man, in sufficient concentration, present for sufficient time and under circumstances which interfere
significantly with the comfort, health or welfare of persons or with the full use of enjoyment of property”.
Bureau of Indian Standards ,IS4167 (1996)
“Air pollution is the excessive concentration of foreign matter in the air which adversely
affects the well being of the individual or causes damage to the property”.
American, Medical Association
Air pollution is not a recent phenomenon: King Edward I of England tried to clear the
smoky sky over London in 1272 by banning the use of coal. The British Parliament ordered
the torturing and hanging of man who sold and burned the outward coal. Under Richard II
(1377-1399) and later under Henry V (1413-1422), England took steps to regulate and
restrict the use of coal.
Such natural processes as forest fires, decaying vegetation, dust storms and volcanic eruptions have
always contaminated (to add a substance which will make something dirty or harmful) the air.
Although the total global production of many gases and particulate matter recognised as pollutants is
much greater from natural resources than from man-made sources, but global distribution and
dispersion of those natural pollutants result in low average concentrations.
By precipitation, oxidation (the addition of oxygen to a molecule or the removal of
hydrogen. Reduction is therefore the addition of hydrogen or the removal of oxygen) and absorption
into the ocean and the soil, atmosphere can clean itself of all known pollutants if given sufficient
time. On the other hand, man generated pollutants are continuously emitted and concentrated in small
geographic region; hence air pollution problem is generally anthropogenic phenomena. Presently the
rate of pollutants discharged into the atmosphere in highly populated regions exceeds the natural
cleaning rate of atmosphere.
The air pollution can be classified as:
i) Personal and indoor air pollution: There is continuous pollution of air inside the house
from various sources. These include smoke, fumes and vapours from the kitchen; fumes
from detergents; particles from cosmetics; rugs, carpets, blankets etc.; tobacco, smoke and
radioactive rays from electronic gadgets like T.V., Computer etc.
ii) Community air pollution: Our community air gets polluted by burning of firewood, coal
and cow dung cakes, automobiles exhaust, decaying of plants and animals and dust from
streets and industries around communities.
iii) Occupational air pollution: Air pollution which occurs in the industries, mines or any
other work areas is restricted to the workers of an occupation. For example those who work
in the mines may have black lung disease due to coal particles.
Air Pollutants
Air pollutants are substances, which contaminate the air and cause harmful effects to man, animals,
plants and buildings etc.
The major man-made pollutants, which get added in the air, are carbon dioxide, carbon monoxide,
oxides of nitrogen, ozone and metal particles of lead, nickel, arsenic, cadmium etc.
There are some natural pollutants released in the air. These include pollen grains, spores, cell of fungi
or lower plants, gases from volcano, marsh gas etc.
Sources of Air Pollution can be broadly classified as:
• Natural Sources; and
• Anthropogenic (man-made) Sources.
The natural sources of air pollution occur naturally. As man cannot control nature, therefore
air pollution by natural sources cannot be controlled. A few natural sources are pesented
below:
i) Volcanic Eruptions: Eject pollutants like particulate matter, dust, fly ash along with
various gases, such as, sulphur dioxide (SO2)'
ii) Process of Pollination: This process is carried out by plants with the help of wind. In
this case the pollen grains are carried away by wind as pollutants.
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iii) Desert Storms or Dust Storms: In the deserts or arid or semi-arid areas, the sand or
dust particles are carried by wind as pollutants. This is due to absence of moisture in the
soil.
iv) Forest Fires: These fires are caused due to friction of trees or grass against each other
or by lightning striking on them. the pollutants obtained from forest fires are Carbon
monoxide (CO), Carbon dioxide (CO2), particulates, Hydrocarbons (HC), Oxides of
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Air Pollution caused by human activities are termed as anthropogenic
pollution, it is further classified as stationary sources, and mobile-sources.
i) Stationary Sources
Various stationary sources include industrial and commercial process,
generation of heat or power (electricity), stationary engines, home heating,
cooking, refuse burning, incineration (burning of hazardous material at
high temperature), and use of solvents/ aerosols (suspension of particles or
droplets in the air).
ii) Mobile Sources are
Line Source: highway vehicles, trains, and channel vessels.
Area Source: railway yards, port vessels, junctions, and aerodrome.
Air pollution has many adverse effects. It not only effects health of people but also has adverse
effects on soil, plants, monuments and buildings and climate etc.
* Effects on Health
* Effects on Soil
* Effects on Plants
* Effects on Monuments and Buildings
* Other Effects of Air Pollution
-Smog
-the green house effects
-acid rain
-ozone depletion
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Effects on Health: Air pollution is very injurious to health. It can cause various problems
ranging from minor ailments to blindness, respiratory distress and death as it happened in
Bhopal Gas Tragedy on 3rd December 1984. The severity and nature of problems depends
upon the type and concentration of pollutant in the air.
The air pollution can cause the following disorders in human beings:
a) Respiratory disorders: Generally air pollution cause irritation of nose and throat,
respiratory damage which includes bronchitis, asthma, emphysema and infection of
respiratory tract. These problems are due to nitrogen oxide, sulphur dioxide, ozonc,
suspended particulates, fluorides and aldehydes.
b) Heartproblems: Carbon monoxide is found to cause heart disorders. Carbon monoxide
reduces oxygen in the blood, which increases the risk of heart attacks. Other pollutants such
as sulphur dioxide, ozone and suspended particulate matter can also cause heart diseases.
c) Brain damage and nervous breakdown: Lead and hydrogen sulphide can cause brain
damage. Lead can cause permanent brain damage and reduce ability to concentrate,
irritation and hyper activity in children below five years. Children may become below
average in growth and development.
d) Cancer: Inhalation of diesel and petrol exhalist can cause lung cancer because of carbon
particles and benzene. Some of the hydrocarbons can cause anaemia and blood cancer.
e) Eye problems: Air polluted with nitrogen oxide, sulphur dioxide and ozone etc. can cause
irritation, conjunctivitis and even blindness like in Bhopal Gas Tragedy mentioned earlier.
f) Birth effects and stunted growth in children: Particulate matter, polluted air, cigarette
smoke and vehicle exhaust which contain carbon monoxide and benzene can produce low
birth weight babies with stunted growth. Chances of abnormal babies are high to mothers
who smoke during pregnancy.
ii) Effects on Soil: Air pollution abrades, corrodes and tarnishes soil. These effects reduce
the fertility of soil.
iii) Effects on Plants: Air pollutants cause disappearance of chlorophyll (the green colouring
matter) which is responsible for photosynthesis, breakdown of plant cells and premature
leaf fall. Ozone mainly affects field crop, fruit and fruit trees.
iv) Effects on Monuments and Buildings: Monuments like Taj Mahal are facing grave
danger from air pollution. The black soot released from Mathura oil refineries is causing
blackening of Taj Mahal.
v) Other Effects of Air Pollution
a) Smog: Smoke mixed with fog is called smog. This usually happens during the months of
December and January in traffic chocked roads and industrialized cities and towns of our
country. It can be very injurious if it contains sulphur dioxide, carbon monoxide and
nitrogen oxide in sufficient quantity. As it happened in London in 1952 when 4000 people
died and in tokyo in 1972, 8000 people died.
b) The green house effect: Normally the solar energy from the sun reaches the earth to be
utilized by plants and animals. Heat is produced in this process, which gets radiated in the
space. Thus the temperature of earth surface is maintained.
But because of the air pollution, due to fuel burning, carbon dioxide and water vapours,
which are released, form a layer along with ozone in the atmosphere. This layer allows the
solar energy to pass through on the earth surface but traps the heat back in the earth's
atmosphere resulting in gradual warning of earth’s atmosphere. This is effecting change in
the weather.
c) Acid rain:
The pollutants, sulphur dioxide, nitrogen oxide which are released by burning of coal and
petroleum products combine with moisture in the air and rain water and produce sulphuric
acid and nitric acid respectively and fall along with the rain called as acid rain. The acid rain
pollute soil, water and reduces the growth of crops and fishes in river, streams, canals and
ponds. It also stops the growth of plants and destroys: the buildings made of marble and
stones and statues made up of metals, Acid rain can cause respiratory problems such as
asthma, bronchitis and emphysema.
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d) Ozone depletion:
Though presence of ozone in the earth’s atmosphere is harmful but it is presence 25-40 km
above the earth’s surface, protects living things from the harmful Ultra Violet (UV) rays. It
forms a kind of protective shield and prevent penetration of UV rays. Thus protects human
beings from skin cancer and cataract. But this layer is now getting depleted because of
pollutants like carbon dioxide, water vapours etc. 1t makes the UV rays to reach on the
earth and increase the risk of skin cancer.
Air pollution is thus very injurious to both living and non-living things in the biosphere. It
causes many disorders which are fatal. The sudden air pollution as happened in Bhopal Gab
Tragedy can lead to severe respiratory distress and suffocations and deaths 'in large number
of people at a time.
e) Green House Effect
Human activities during the fast few centuries have polluted the atmosphere to the extent
that it has begun to seriously affect the climate. The carbon dioxide in the atmosphere has
increased by 31 per cent since pre-industrial times, causing more heat to be trapped in the
lower atmosphere. There is evidence to show that carbon dioxide levels are increasing.
Many countries have signed a convention to reduce greenhouse gases (GHGs) under the
United Nations Framework Convention on Climate Change (UNFCC). However, the
current international agreements are still not effective enough to prevent the significant
changes in climate and a rise in sea level.
Fossil fuel consumption agricultural, deforestation and present land-use practices contribute
to the CO2 buildup. Continued CO2 buildup will lead significant enough rise in earth
surface temperature to melt the Arctic ice pack. If the warming trend can be confirmed and
positively linked to CO2 build up, then global action, such as, reforestation may eventually
have to be pursued to remove CO2 from the atmosphere. In fact, this seems to be the case.
About 75 per cent of the solar energy reaching the earth is absorbed by earths surface,
which increases its temperature. The rest of the heat radiates back to the atmosphere. Some
of the heat is trapped by green house gases (GHGs), mostly carbon dioxide. As carbon
dioxide is released by various human activities, it is rapidly increasing. This is causing
global warming.
There is at present some uncertainty about the effect of global warming if it is allowed to
continue. What harmful changes will occur if present trends continue is not a doubt but only
doubt is about when and where they will occur and -their overall magnitude .
Air pollution can cause many health disorders in man related to
respiratory system, cardiovascular (heart) system, nervous system, eye etc.
Usually these problems occur very gradually due to long exposure. But
these turn out to be very serious problems by the time they are diagnosed.
These problems can be prevented and controlled by prevention and
control of air pollution. The methods of prevention and control of air
pollution:
i) Containment method: In this method the pollutants are prevented from their source into
the air. This can be done by various mechanical devices e.g. enclosure of exhaust, air
cleaning before discharge, suction ventilation. Most of these methods are used in various
factories.
ii) Replacement method: In this method pollution producing substances and processes are
replaced with non polluting substance and process e.g. use of CNG instead of diesel/petrol
in automobiles, use of non leaded petrol, instead of leaded petrol, use of Gobar gas/natural
gas instead of firewood and coal for cooking, replacement of coal based electricity
production plants by hydroelectric power or wind powered generators etc.
iii) Dilution: Dilution/reducing of pollutants in the air can be done by extensive planting of
trees and vegetation around industrial and residential areas. This is usually called as
establishing of green belts.
iv) Legislative method: It refers to establishing of act (law) which can set some norms for
precautionary measure to be implemented by the factories, automobiles etc. The
Government of India has enacted Air (Prevention and Control of Pollution) Act 1981.
Usually difficulties are experienced in implementation of the act.
v) International action: Air pollution is considered a global problem. Therefore, WHO has
established regional centres at London, Washington, Moscow, Nagpur and Tokyo and 20
laboratories in various parts of the world. These laboratories and cities are set up to study
the air pollution level and issue warning of air pollution where and when necessary.
vi) Mechanical ventilation: Mechanical ventilation especially in houses, public places,
health centres and hospital wards help in removing used air and replacing it with fresh air.
It also reduces the bacterial content.
vii) Dust control: Dust control can be done by frequent wet dusting and bathing of floors of
health centres, hospital wards, houses, roads etc. This not only reduces dust but also the
bacterial content.
viii) Management of transport and road traffic: Pollution can be reduced by:
* Good public transport system so that people travel by this system and not by individual
cars.
* Car-pooling which win discourage using individual car.
* Better traffic management, which will help in reducing congestion on road and lessen air
pollution.
Not any one method is self sufficient in prevention and control of air pollution. It requires
the implementation of all these methods to have good effects.
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