Download Untitled-9

CHAPTER 2: Topic: POLLUTION-AIR
Learning Objectives
In this lecture, you will learn:
•
Awareness about the pollution created by the man.
•
What is pollution
•
What are pollutants
•
What are the types of pollution & pollutants
•
What are the causes of air pollution
•
Effects of air pollution
Introduction
Progress in agriculture and industry is taken a general criterion of development of any country. This craze
resulted into unlimited exploitation of every bit of natural resource. The splendid plentifulness of nature is a
heritage that should be conserved for future generations and not be spoiled.
Such activities of man had adverse effect on all forms of living organisms in the biosphere. The earth planet
along with the atmosphere (air, land, water) that sustains life is called the biosphere. Biosphere extends into
about 7 km. of the earth surface itself, downward into the ocean to depths of about
10.67 km. and vertically into the air to about 10 km., where life is found to exist
Unlimited exploitation of nature by man disturbed the delicate ecological balance between living and non-living
component of the biosphere. The unfavorable conditions created by man himself threatened the survival not only
of man himself but also other living organisms. The number of the species likely to become rare, threatened,
endangered or near extinction in the Red Data Book of the IUCN is increasing with time. It is very common to find
warnings at public places, reading as “Air unfit for breathing”, “Water unfit for drinking”, “Do not eat fish caught
here” and so on.
India today is one of the first ten industrialised countries of the world. Today we have a good industrial
infrastructure in core industries like metals, chemicals, fertilisers, petroleum, food etc.
What Has Come Out of These?
•
Pesticides, detergents, plastics, solvents, fuels, paints, dyes, food additives etc. are some examples.
•
Progress in atomic energy, resulted in increase in radioactivity in the biosphere.
•
There are a number of industrial efl1uents and emissions particularly poisonous gases in the atmosphere.
•
Mining activities also added to this problem particularly as solid waste.
Pollution is a man-made problem, mainly of effluent countries. The developed countries have been in a mad race
to exploit every bit of natural resource to convert them into goods for their comfort, and to export them to needy
developing world. In doing so, the industrialized countries dump lot of materials in their environment which
becomes polluted. In one-way pollution has been in fact “exported” to developing countries.
What is Pollution?
Pollution is an undesirable change in the physical, chemical or biological characteristics of air, water and soil that
may harmfully affect the life or create a potential health hazard of any living organism. Pollution is thus direct or
indirect change in any component of the biosphere that is harmful to the living component(s), and in particular
undesirable for man, affecting adversely the industrial progress, cultural and natural assets or general
environment.
What are Pollutants?
Any substance which causes pollution is called a pollutant. A pollutant may thus include any chemical or
geochemical (dust, sediment, grit etc.) substance, biotic component or its product, or physical factor (heat) that is
released intentionally by man into the environment in such a concentration that may have adverse harmful or
unpleasant effects. A pollutant has also been defined as “any solid, liquid or gaseous substance present in such
concentration as may be or tend to be injurious to the environment. Pollutants are the residues of things we make,
use and throwaway. There are many sources of such pollutants. The lakes and rivers are polluted by wastes from
chemical and other factories, and the air by gases of automobile exhausts, industries, thermal power plants etc.
There has grown up a serious concern all over the world about the rivers turning murky, fish rotting on sea
shores, tree withering, cities choking with foul air, toxic chemicals being cycled into food stuffs and disease
epidemics appearing so frequently.
Environmental Pollutants
The various principal pollutants which pollute our air, water, land are as follows:
1
Deposited matter - Soot, smoke, tar, dust, grit etc
2
Gases - Oxides of nitrogen (NO, NO), sulphur (S02)’ carbon monoxide, halogens, (chlorine, bromine,
iodine),
3
Acids droplets - Sulphuric, acid, nitric acid etc.
4
Fluorides
5
Metals - Mercury, lead, iron, zinc, nickel, tin, cadmium, chromium etc. (BC-4)
6
Agrochemicals - Biocides (pesticides, herbicides, fungicides, nematicides bactericides, weedicides etc),
and fertilisers.
7
Complex organic substances - Benzene, ether, acetic acid, benzpyrenes etc.
8
Photochemical oxidants - Photochemical smog, ozone, peroxyacetyl nitrate (PAN), peroxybenzoil nitrate
(PBzN), nitrogen oxides, aldehydes, ethylene etc.
9
Solid wastes
10
Radioactive waste
11
Noise
In UNEP document, the order of priority of different pollutants has been dictated as follows (Table 5.1):
Cost of Pollution
Cost of pollution can be evaluated in the following ways
1. Medical care of health due to diseases as tuberculosis, typhoid, lung cancer etc.
2. Loss of resources by unnecessary wasteful exploitation.
3. Pollution control involving money, funds, manpower etc, for disposal of pollutants and for control devices
developed.
4. Corrosion of metals as iron, steel, copper, brass, nickel, zinc, lead etc. Damage to crop production, and
5. Soiling of buildings (including historical monuments) and textiles.
Kinds of Pollution
Various types of pollutions are classified in different ways. On the basis of the type of environment being
polluted, we may recognise air pollution, water pollution, land (soil) pollution, marine pollution etc. On the basis
of the kind of pollutant involved, we may have sulphur dioxide pollution, fluoride pollution, carbon monoxide
pollution, smoke pollution, lead pollution, mercury pollution, solid waste pollution, radioactive pollution, noise
pollution etc. Of the variety of pollutants, we recognise the following two basic types of pollutants: nondegradable and biodegradable.
1. Nondegradable pollutants These are the materials and poisonous substances like aluminium cans, mercuric
salts, long-chain phenolics, DDT etc. that either do not degrade or degrade only very slowly in nature. They are
not cycled in ecosystem naturally. They not only accumulate but are often biologically magnified with
their subsequent movement in food chains and biogeochemical cycles.
2. Biodegradable pollutants They are the domestic wastes that can be rapidly decomposed under natural
conditions. They may create problems when they accumulate (i.e. their input into the environment exceeds
their decomposition).
Fig 5.1: The picture depicts the movement of pollutant through land water & atmosphere
To start with the types of pollution first, we will start with medium air and study its causes and effects on life
What is Air Pollution?
The earth’s vertically extended atmosphere, an envelope of gases is divided into the following layers:
1. Troposphere (up to 5 Km) - The lowest atmosphere in which temperature decreases with height bounded by
land or sea surface below and by tropopause above,
2. Stratosphere (5 to 45 Km) - the region above the troposphere, in which temperature increases up to 90°C with
height. This is limited by stratopause,
3. Mesosphere (45 to 80 Km) - the part between stratosphere and thermosphere (ionosphere). Temperature again
decreases up to - 80°C.
4. Thermosphere (ionosphere) - above 80 Km, the upper part in which temperature increases with height. There
is no boundary between the atmosphere and void of outer space.
About 75% of the earth’s atmosphere lies within 16Km. of the surface and 99% of the atmosphere lies below an
altitude of 30 Km.
The atmosphere is an insulating blanket around the earth. It is source of essential gases, maintains a narrow
difference of day and night temperatures and provides a medium for long-distance radiocommunication. It also
acts as shield around the earth against lethal UV radiations and meteors. Without atmosphere, there will be no
lightening, no wind, no clouds, no rains, no snow and no fire.
Normal composition of clean air at or near sea is as follows (Table 5.2):
What is Air Quality?
Unfortunately, the concentration levels of different gases show variations due to pollution. Moreover, there are
also added a number of harmful gases to atmosphere. These adversely affect air quality and make it unfit for live
organisms.
Although, there are several parameters to judge air quality, generally three - S02, NOx and SPM (suspended
particulate matter) are used which give a fair idea of pollution load carried by the air.
What are the Causes of Pollution?
The causes of pollution are urbanisation, industrialisation, motorization, energy production from thermal plants,
burning of domestic fuel, burning of agricultural wastes and development in urban settlements. Parallel to rapid
population growth, there has been increased population density in cities causing more pollution and sites for
urbanisation and industrialisation have been incorrectly chosen. Air pollution results from gaseous emissions
from mainly industry, thermal power stations, automobiles, domestic combustion etc.
Urbanisation: The rapid urbanisation that has been taking place is one of the most important causes of the air
pollution. The pollution in cities is known to arise to a larger extent from fuel burning techniques and poor fuel
quality. Among the developments affecting air pollution in cities, many other factors in addition to population
density play important role.
These include incorrect urban settlements according to topographic and meteorological conditions, incorrect
plot division, low quality fuel and incorrect burning techniques, dearth of green areas, increase in the number of
motorized vehicles and inadequate disposal of wastes.
Industrialization: The air pollution caused by industry is principally a result of incorrect selection of site and
emission of waste gases into the air without taking adequate technical precautions. Areas affected to large extent
by air pollution at present are due to presence of paper, sugar, food processing, textile, steel, pesticides, leather and
energy producing industries.
Petroleum refineries are the major source of gaseous pollutants. The chief gases are SO2 and NOx. Cement
factories emit plenty of dust, which is potential health hazard. Stone crushers and hot mix plants also create a
menace. The SPM levels in such areas of stone crushing are more than five times the industrial safety limits. There
are many food and fertilizers industries, which emit gaseous pollutants. There are also chemical manufacturing
industries, which emit acid vapors in air.
Motorization: Traffic also contributes large part to the air pollution. This is because of inferior quality of fuel
material, outdated engines and overloading of motor vehicles. Road traffic in particular is much more damaging
to the environment than railway traffic.
In the major metropolitan cities, vehicular exhaust accounts for 70% of all CO, 50% of all hydrocarbons, 30-40%
of all oxides and 30% of all SPM. The two-wheelers and three-wheelers contribute 60% of the total CO and 83 %
of total hydrocarbons, whereas heavy traffic vehicles 55 to 80% of the oxides of nitrogen.
Chief sources of emission in automobiles are (i) exhaust system, (ii) fuel tank and carburettor and (iii) crankcase.
The exhaust produces many air pollutants including unburnt hydrocarbons, CO, NOx and lead oxides. There are
also traces of aldehydes, esters, ethers, peroxides and ketones which are chemically active and combine to form
smog in presence of light. Evaporation from fuel tank goes on constantly due to volatile nature of petrol, causing
emission of hydrocarbons. The evaporation through carburettor occurs when engine is stopped and heat builds up,
and as much as 12 to 40 ml of fuel is lost during each long stop causing emission of hydrocarbons. Some gas vapor
escapes between walls and the piston, which enters the crankcase and then discharges into the atmosphere. This
accounts for 25% of the total hydrocarbon emissions of an engine.
What are the Types of Pollutants
From the different sources of air pollution, a variety of pollutants are released into atmosphere. The principal air
pollutants emitted from these different sources are as follows:
1. Carbon compounds. These are mainly CO2 and CO, the former release by complete combustion of fossil fuels
and the latter by automobile exhausts,
2. Sulphur compounds. These include S02' H2S and H2SO4' mostly released by fossil fuel (coal etc.) based
power generating plants and industrial units as refineries.
3. Nitrogen oxides. These include chiefly NO, N02, HN03, mostly release by automobiles, power plants and
industries.
4. Ozone. (O3) Its level may rise in atmosphere de to human activities,
5. Fluorocarbons. These come from industries, insecticides spray etc.
6. Hydrocarbons. These are chiefly benzene, benzpyrene etc. which are mostly discharged by automobiles and
industries.
7. Metals. These include chiefly lead, nickel, arsenic, beryllium, tin, vanadium, titanium, cadmium etc., present in
air as solid particles or liquid droplets or gases. They are produced mostly by metallurgical processes, automobile,
seaspray etc.
8. Photochemical products. These are the photochemical smog, PAN, PBzN etc., released mostly by automobiles.
9. Particulate matter. These are fly, ash, dust, grit and other suspended particulate matter (SPM) released from
power plants and industries (stone crushers etc). There are also bacterial cells, fun gel spores, and pollens in air as
biological particulate pollutants.
10. Toxicants other than heavy metals. Complex chemical substances released during manufacture of other goods.
Table 5.3: Classification of air pollution sources and emissions
Carbon Compounds
1. Carbon monoxide (CO)
Properties: is a (a) colourless, (b) odourless, (c) highly toxic gas, (d) occurs in the atmosphere in trace amounts
(e) generated when carbon containing material burns with insufficient oxygen; discharged from gasoline
engines and burning of coal; burning of firewood and wood waste. Approximately 200 million tonnes of carbon
monoxide is poisoning the global atmosphere every year.
Causes
a. Adverse breathing effect as it interferes with absorption of oxygen by the red blood cells. It combines with
haemoglobin in human blood to formcarboxyhaemoglobin, which impairs oxygen transport.
b. The normal functioning of the nervous system can be affected by the presence of 2-5 per cent of
carboxyhaemoglobinin the blood which may occur after breathing air with only 30 ppm of CO.
c. It may cause giddiness and headache in less than one hour at a concentration of 100 ppm and’ such situations are
common during traffic jams.
d. At higher concentration, it is lethal to man and many other
living organisms. On global basis, 90 per cent of the total CO originates from the oxidation of methane
production by decaying organic matter. However, man-made CO emission, which up to 90 per cent arises from
the transport sector, mainly automobiles, is responsible for relatively high local concentration in most of the
industrialised nations. In Delhi alone, about 250 tonnes of CO is released in the atmosphere per day, which
reduces the respiratory capacity of the people.
2. Carbon dioxide (CO2)
Properties: is a natural component of the earth’s atmosphere, human activities increases the amount, released
from burning of fossil fuels, oxidation of carbon stored in trees, soil humus, released when forests are fired for
shifting cultivation. It plays a vital role in global carbon circulation through the environment and is a main feed
stock for the photosynthesis process in green vegetation.
Causes: increase of atmospheric level effects directly plant life and biosphere, whereas indirect effects are
through climatic, changes, such as increase in global temperature leading to change in rainfall pattern, shifting
of productive land into desert like condition, melting of ice in the polar region of the world which will result in
rising of sea level, and change in fish production, forest and water supply.
At present, the concentration of CO2 in the atmosphere is approximately 350 ppm, and the annual rate of
increase of CO2 0.7 mg/1.
Sulphur Compounds
1. Sulphur dioxide (SO2)
Properties: is a colourless gas with a suffocating and strong pungent odour, released from industrial processes
and burning of sulphur-containing coals or heavy oil, particularly in thermal power plants. In the atmosphere,
sulphur dioxide combines with oxygen and water to form sulphuric acid (H2SO4) the major component of acidic
rain. On global scale about half of the ambient S02 originates from the oxidation of hydrogen sulphide (H2S)
given off by decaying organic matter.
Causes: Long-term or chronic exposures to S02 have been linked to the increased incidence of respiratory
diseases such as bronchitis, particularly in young children. It causes irritation in throat and eyes, chest
constriction, headache, vomiting and death. Monocotyledonous plants are more
sensitive to S02 and it causes damage to cereal crops, conifer
forests and apple orchards. Every year, 80 million tonnes of
S02 is poisoning the air of our earth.
2. Hydrogen Sulphide (H2S):
Properties: Chief source is decaying vegetation and animal,
matter, especially aquatic habitats. Sulphur springs, volcano
eruptions, coal pits & sewers gives this gas. Chief industrial
source is sulphur containing fuels.
Causes: At low concentration, causes headache, nausea, collapse, coma and final death. Concentration of 150ppm
causes conjunctivitis and irritation of mucus membranes. This gas readily passes alveolar membranes of lungs and
penetrates the blood stream. Death occurs due to respiratory failures.
Nitrogen Oxides (NOx)
Properties: the oxides of nitrogen- nitric oxide (NO) and nitrogen oxide (NO2) emitted from the transport sector,
energy and industrial sectors equally. The major sources of oxides of nitrogen are motor vehicle exhausts, soft
coal burning and acid manufacturing, globally; about 60 per cent of oxides are produced from natural resources,
including biomass burning, fixation by lighting, inflow from the stratosphere, chemical conversion from ammonia
in the troposphere and loss of gaseous nitric oxide from the soils.
Causes: have direct and indirect effects on human life and environment; inhibit cilia action so that soot and dust
penetrate lungs to cause bronchitis and other respiratory diseases. N02 combines with water to form HN03 which
forms a part of acid rain. It plays a great role in formation of smog in acid and humid conditions.
About 10 million tonnes of nitrogen containing gases like NO and N02 are entering into the atmosphere every
year.
Ozone
Properties: present in significant concentration in both stratosphere and troposphere. It has a pleasant odour but
causes irritation when present in higher amounts. It is used as a disinfectant for air and water, and in industry for
bleaching waxes and oil, as well as for organic synthesis. Ozone is produced in the atmosphere through the
interaction of nitric oxide, sunlight and hydrocarbons. It is considered to be the major component of
photochemical smog:
Motor vehicles exhaust very high amount of ozone in the atmosphere. It plays a vital role in the photo-chemical
formation of air pollutants. Its presence in the stratosphere serves to reduce strongly the amount of short-wave
ultraviolet (UV) radiation at wavelength below 310 nm reaching the earth. This natural screening is necessary for
human and other living organisms.
Causes: The UV radiation at 290 nm, for example, is 10,000 to 1, 00,000 times more effective in damaging DNA
(deoxyribonucleic acid), than is UV radiation at longer wave-length of 320 nm. The main concern about more
short-wave UV radiation reaching the ground is the possible increase in the occurrence of human skin cancer. It
might also damage the animal and plant life and possibly reduce the rate and efficiency of photosynthesis, and
hange in the ozone layer might also affect the global climate.
Fluorocarbons
Properties: It is in gaseous or particulate state. Fluorides in atmosphere come from industrial processes of
phosphate fertilisers, ceramics, aluminium, fluorinated hydrocarbons (refrigerants, aerosol propellants etc),
fluorinanted plastic, uranium and other metals. In air, fluoride chiefly comes from smoke of industries, volcanic
eruptions and insecticide sprays.
In particulate form it is deposited near the vicinity of emission, whereas in gaseous form becomes dispersed over
large areas. On an average fluoride level of air is 0.05 mg/m3 of air.
Causes: In minute amounts, fluorocarbons are beneficial helping prevention of tooth-decay in man. However,
higher levels become toxic. In India, there is problem of fluorosis, as also in other countries as U.S.A., Italy,
Holland, France Germany, Spain, Switzerland, China, Japan and some African and latin American countries.
Fluorides enter plant leaves through stomata. In plants it causes tip burn due to accumulation in leaves of conifers.
Fluoride pollution in man and animals is mainly through water.
Hydrocarbons
The chief air pollutants are benzene, benzpyrene and methane, emitted by evaporation of gasoline through
carburettors, crankcase etc. produced by two and three-wheelers, constituting about 65% of the total
hydrocarbons.
They have carcinogenic effects on lung. They’ combine with NOx under UV -component of light to form other
pollutants like PAN and O3 (photochemical smog) which cause irritation of eye, nose and throat, and respiratory
distress.
Benzene a liquid pollutant is emitted from gasoline. It causes lung cancer. Benzpyrene is most potent cancer
inducing hydrocarbon pollutant. It is also present in small amounts in smoke, tobacco, charcoal boiled stakes,
and gasoline exhaust.
Methane (marsh gas) is a gaseous pollutant, in minute quantity in air, about 0,0002% by volume. In nature this is
produced during decay of garbage, aquatic vegetation etc. This is also released due to burning of natural gas and
from factories. Higher concentrations may cause explosions. The excess of water seepage in filled up well and pits
may lead to excess production of methane which bursts with high sound and may cause local destruction. At high
levels in absence of oxygen, methane may be narcotic on man.
Metals
In air, the common metals present are mercury, lead, zinc and cadmium released from industries and human
activities in the atmosphere.
Mercury: a liquid volatile metal (found in rocks and soils) is present in air as a result of human activities as the
use of mercury compounds in production of fungicides, paints, cosmetics, paper pulp etc.
Causes: inhalation of 1 mg/m3 of air for three months may lead to death. Nervous system, liver, eyes are
damaged. Infant may be deformed. Other symptoms of mercury toxicity are headache, fatigue, anxiety, lethargy,
loss of appetite etc.
Lead: Lead is a metal and exists in a variety of chemical compounds with different characteristics. The
atmospheric lead contamination comes largely from the automobiles. Lead can enter the environment from many
sources; the mining and smelting of lead bearing ores and metals, lead plumbing and solder paints and ceramic
glass, and the careless disposal of lead-zinc batteries in the open space. The lead levels of air in air-quality guide of
WHO are 2 Jlg/m3.
Causes: inhalation causes reduced hemoglobin formation, thus leading to anemia, lead compounds also damage
RBCs resulting in infections of liver and kidney in man. In automobiles lead accumulation increases emission of
hydrocarbons.
Zinc: not a natural component of air occurs around zinc smelters and scrap zinc refineries. Copper, lead and steel
refineries also release some zinc in the air. Open hearth furnaces emit 20-25 g zinc/hr in refining the galvanised
iron scrap; Zinc in air occurs mostly as white zinc oxide fumes and is toxic to man.
Cadmium: occurs in air due to industries and human activities. Industries engaged in extraction, refining,
electroplating and welding of cadmium-containing materials, and those in refining of copper, lead and zinc are the
major source of cadmium in air. Production of some pesticides and phosphate fertilisers also emits cadmium to
air. This metal is emitted as vapour, and in this state it quickly reacts to form oxide, sulphate or chloride
compounds. Cadmium is poisonous at very low levels and is known to accumulate in human liver and kidney. It
causes hypertension, emphysema and kidney damage. It may turn to be carcinogenic in mammals.
Photochemical Products
There is much interlinking of NOx hydrocarbons and O3 in the atmosphere, these individually are recognised air
pollutants. However, at the same time in presence of light as a result of photochemical reactions these may react
with each other and/or may undergo transformations to produce even more toxic secondary pollutants in the air.
There are also some other pollutants. The principal photochemical products are olefins, aldehydes, ozone, PAN,
PB2N and photochemical smog.
a. Olefins: produced directly from the exhaust and in the atmosphere from ethylene. At very low concentrations,
they affect plants seriously. They wither the sepals of orchid flowers, retard the opening of carnation flowers and
may cause dropping of their petals. At high levels they retard the growth or tomatoes.
b. Aldehydes: as HCHO and olefin, caroling irritate the skin, eyes and, upper respiratory tract.
c. Ozone.
d. The aromatics photochemical products are the most potent pollutants.
1. Benzpyrene is carcinogenic at about 1 ppm or less. But at higher concentration it is more lethal than S02 but less
lethal than O3, and has same effect as by NOx. PAN and O3 both cause respiratory distress and are toxic to plants.
NOx and PAN cause death of forest trees. PAN is produced due to reaction between NOx and hydrocarbons under
effect of UV -radiation of sunlight, when O3 is also formed. PAN blocks Hill reaction in plants. It causes injury in
spinach, beets, celery, tobacco, pepper, lettuce, alfalfa, aster, primose etc. It causes silvering of the underside of
leaves.
e. Photochemical smog is highly oxidising polluted atmosphere comprising largely of O3, NOx, H2O2, organic
peroxides, PAN, and peroxybenzoil nitrate (PBzN). This is produced as a result of photochemical reaction
among NOx, hydrocarbons and oxygen. The photochemical smog formation occurred only during night or
cloudy days. Smog with mixture of reducing pollutants is called reducing smog, whereas with mixture of
oxidising pollutants is called oxidising smog or photochemical smog.
Photochemical smog adversely affects plants, human health and materials. The oxidants enter as part of
inhaled air, and alter, impair or interfere with respiratory process. Causes diseases as asthma and bronchitis in
epidemic form (Tokyo-Yokohama asthma in 1946). Another serious disease caused by smog is emphysema, a
disease due to structural breakdown of alveoli of 1ungs. The total surface area available for gaseous exchange
is reduced and this causes severe breathlessness.
Particulate Matter
Particulate matter constitutes about 5 per cent of the weight of all pollutants present in the atmosphere, includes
those air pollutants which may be in the form of solid particles or liquid droplets (aerosols) including fumes,
smoke, fog, dust, pollen, bacteria, viruses and aerosols.
There are four types of sources of PM: (i) fuel combustion and industrial operations (mining, smelting, polishing,
furnaces and textiles, pesticides, fertilisers and chemical production), (ii) industrial fugitive processes (materials
handling, loading and transfer operations), (iii) nonindustrial fugitive process (roadway dust, agricultural
operations, construction, fire etc.) and (iv) transportation sources (vehicles exhaust and related particles from fire,
clutch and break wear).
Natural dust forms about half of the total mass of particulate matter in the air. Dust has a relatively small impact
because it tends to be coarse. Fine particulate matter (< 2.5 µg dia) is most harmful to human health than the
coarse particulate matter (>
2.5 µg dia). Particulate remains suspended in the air and transported away to a long distance when the strong
wind blows.
Causes: Small particulate matter with a size of less than 2 µg has an important impact on health although it
contributes only about 1 per cent of the particulate load in the atmosphere.
Aerosols can be inhaled and penetrate deep into lungs affecting human health by creating disorders. These
particles carry toxic metals and other toxic substances.
What are the Effects of Air Pollution?
Air pollution has both direct and indirect impact on human body, animal life, plant kingdom, construction
materials, climate and entire ecosystem. These effects have both long-term and short-term implications, and
influence the economy and welfare of the human-beings. Out of these, the effects of air pollutions on human
health are of great concern.
1. Human Health
Air is a fundamental element of human life as it makes breathing possible. Pollutants enter into the human
lungs through the following mechanisms:
•
In the respiratory system, which reacts by the initiation of constructive reaction of a bronchi reflex
•
In the blood vessels of the bronchus and its branches, which try to reduce the absorption of harmful
substances through the bronchial mucosa
•
In the blood vessels of the lungs, where they react by decreasing absorption from the alveolar (pulmonary)
capillaries
Pollution in the air is thus of utmost importance from the viewpoint of human health. Pollutants in the air, such as
carbon particles, ozone, carbon monoxide, sulphur dioxide, unsaturated hydrocarbons, aldehydes, carcinogens,
etc. disrupt the normal mechanism of the human respiratory tract, causing bronchial infection and stenosis,
chronic bronchitis and emphysema (Table 4). Polluted air can also cause discomfort, shortness of breath, and is a
major cause of cancer.
Table 5.4: Acute and chronic physiological effects of major air pollutants on human beings
2. Plants
In addition to human beings, plants too are faced with the harmful effects of polluted air. Plants have a very close
interrelation with the environment through absorbing CO2 from the atmosphere and releasing oxygen in the air.
All forms of life on this earth are directly or indirectly dependent upon plants as a source of food. Plants also act
significantly improving our environment ecologically, aesthetically, physically and chemically.
The nature of injuries to plants by various gases can be categorised into two parts:
1. Visible effects, and
2. Suppression of growth.
The extent of injuries or damage of individual plants depends upon:
1. The nature and amount of pollutants,
2. Type of soil,
3. Relative humidity,
4. Amount and type of plant food materials,
5. Stage of plant growth,
6. Viability of the plant,
7. Time of exposure, and
8. Amount of light.
3. Insect Pests
Urban and industrial pollution not only hinders the growth of various useful plants but also promotes the
multiplication and growth of harmful insects of field crops, and increases their efficiency of attacking on green
vegetation.
e.g.: In presence of high level of pollutants, the harmful insects breeds vary well and quickly. eg. long bug
species like Oncopeltus fasciatus, feed well when contents of carbon monoxide, sulphur dioxide and nitrogen
oxide increases.
4. Materials
Air pollution damages materials mainly by corrosion of metals, stones, marbles, etc. from acidic compounds in
polluted atmosphere. The most important acid forming pollutants are sulphur dioxide and nitrogen oxide. In
the presence of moisture, they change into sulphuric acid and nitric acid. Deposition of these acids on the metal
parts of buildings, roof covers, down spouts, and other metal equipment results in a considerable loss form
atmospheric corrosion in industrial sectors. Major areas of economic importance are the side walls of tyres and
various forms of electrical insulation.
e.g.: The surface of the Taj Mahal has lost its luster and has become rough and slightly coloured due various
pollutants from Mathura Refinery.
5. Climate
When atmospheric conditions are changed by air pollution they affect the climate. Generally, the average
temperature in cities is higher than that in rural areas.
It leads to:
•
Increased rainfall in big cities.
•
Abundance of hygroscopic substances results in increased rainfall by making it easier for clouds to form.
•
The layer of pollution formed over a city causes a significant reduction in the amount of ultraviolet light
resulting in decreased exposure to sunlight.
These undesirable developments indicate how air pollution upsets the natural balance of the climate. Other
effects of air pollution at international level are depletion of ozone layer, warming of earth surface, rising of sea
level and acid-rain which are the serious issues facing the entire world now-days.
What are the measures to be taken to combat the effect of air pollution?
Control Measure
The objectives of air pollution controls are:
a. To organize the air quality management in the long term
b. To protect the human beings as well as the plant and animal life, and materials from harmful effects
c. Reducing air pollution in highly polluted areas
d. Retaining the existing air quality in areas currently less polluted. Reducing-the long; range transport of air
pollutants.
Most of our cities exceed primary standards by a considerable amount throughout the year. There are various
fundamental technological and nontechnological approaches to control of air pollution, which are to be used in
one or the other ways .Some of the following remedies can be helpful to minimize the pollution of air.
1. Enforcement of Air (Prevention and Control) Pollution Act, 1981: Air quality standards as recommended by
the Central Pollution Control Board must be strictly implemented.
2. Use of purified fuel: It is possible to reduce the level of lead oxide in the, air taking the lead out of the petrol.
3. Modernizations of out-dated industries and machinery: improvement of industrial processes and vehicle
engines, and make overall expenditure of energy more efficient by modifying old machinery.
4. Installation of air treatment plants: Large number of treatment plants both for air and water purification must
be installed either for individual industry or as common treatment plants. These treatment plants must be run
throughout the clock.
5. Alternative energy sources: The different sources of energy for our society are wind, water and solar energy
6. Installation of devices:
a. Filters: Filters separate out the particulate matter from the stack gases in electric power plants.
b. Cyclones: Cyclones also remove particulate matter. This technique removes 50-90 per cent of large particulate
matter along with a few medium and small particulates.
c. Electrostatic precipitators: Electrostatic precipitators remove the particulate matter and these are 99 per cent
efficient.
d. Scrubbers: These are used to remove both the particulate matter as well as sulphur dioxide gas.
e. Catalytic converters: This device is attached to the exhaust system of the vehicle and converts carbon monoxide
and hydrocarbons into carbon dioxide and water, and nitrogen oxides into nitrogen gas.
7. Subsidized lead-free petrol: Lead-free petrol must be available at the lowest rate so that the vehicle users can
be motivated towards toxic-free fuel.
8. Plantation of trees: Plantation of trees especially, broad leaf plants such as various ornamental trees, forests
and fruit trees keep large amount of gases and dust on their leaves,. twigs and stems, and these tree parts
absorb various pollutants.
9. Change in life style: air pollution can be reduced
•
•
•
•
•
•
Using energy more efficiently,
Relying more on no combustive sources, of energy such as solar and wind energy, restriction of areas in
which any industries shall not be installed or installed subject to certain safeguards,
Planting of pollution tolerant and dust filtering plant species as green belts around industrial and urban
areas,
Maintenance of roads,
Ideal traffic planning and
Removal of unnecessary check posts and barriers.
Table 5.6: Effect of major air pollutants on materials