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 etc2 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 manu-facturing 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 energy6. 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