Category : 12th Class

(3) Qualitative pollutant : The pollutant is a harmful substance, chemical or factor that does not occur in nature but is added by human beings, e.g., insecticide, herbicide.

(4) Quantitative pollutant : It is a normal component of nature that becomes pollutant when its concentration becomes higher than the normal, e.g., nitrogen oxides, carbon monoxide.

(5) Degradable pollutant : The pollutant degrades after some time either automatically (e.g., heat) or through the agency of microorganisms (= biodegradable, e.g., sewage, livestock wastes, market garbage). Biodegradable pollutants are easily disposed off or degraded through natural processes or waste treatment plants. They can be turned into a resource, e.g., compost, manure.

(6) Non-Degradable pollutant : It is a pollutant which does not breakdown or get converted to harmless state by natural processes of dissipation, dispersal, oxidation or biological decomposition, e.g., DDT, glass, plastic. It is also known as conservative or persistent pollutant.

Types of pollution

(1) Natural pollution : It is pollution caused by natural sources, e.g., volcanic eruptions, release of methane by paddy fields and cattle, release of carbon monoxide by plants and animals, emission of natural gas, ozone, nitrogen oxides, soil erosion, dust storms, cosmic rays, ultra-violet rays, etc.

(2) Anthropogenic or Man-made pollution : It is pollution caused by human activities like noise, automobiles, industries, smoking, pesticides etc. Anthropogenic pollution is often quite small in quantity as compared to natural pollution. Example, 0.05% of atmospheric pollution is man-made while 99.95% is natural pollution.

  • On the basis of source of pollution, it can be :

(1) Air pollution : Air or atmospheric pollution is the addition of materials or chemicals into atmosphere in such concentration that they begin to exert adverse effect on human beings, other desirable species, human assets and resources. Total amount of air pollutants is estimated to be \[1\times {{10}^{12}}\] tonnes, out of which pollutants added by human activities are only \[5\times {{10}^{8}}\] tonnes or 0.05%.

(i) Air Pollutants : The common air pollutants are : Dust, Smoke, Carbon monoxide \[(CO),\] Ammonia \[(N{{H}_{3}}),\] Sulphur dioxide\[(S{{O}_{2}}),\] Hydrogen sulphide \[({{H}_{2}}S),\] Nitrogen dioxide \[(N{{O}_{2}}),\] Hydrogen cyanide, Hydrogen fluorides, Chlorines, Phosgenes, Arsines, Aldehydes, Ozone, Ionising and radiations. \[C{{O}_{2}}\] is not a normal air pollutant. There is 0.03% \[C{{O}_{2}}\] in the air its higher percentage is the cause of green house effect.

Types of air pollutants : It is of two types :  

(a) Primary air pollutants : Air is polluted by poisonous gases and undesirable substances. They are released by burning fossil fuels. These substances are called primary air pollutants. The primary air pollutants are the following :

  • Soot released from unburned fuel.
  • Sulphur dioxide (SO2).
  • Benzopyrene (hydrocarbon) released from cigarette smoke.
  • Ammonia \[(N{{H}_{3}}).\]
  • Oxides of nitrogen.
  • Carbon monoxide (CO).
  • Lead (Pb).

(b) Secondary air pollutants : Secondary air pollutants are poisonous substance formed from primary air pollutants. In bright sun light nitrogen, nitrogen oxides, hydrocarbons and \[{{O}_{2}}\] interact to produce more powerful photochemical oxidants like ozone \[({{O}_{3}}),\] peroxyacetyl nitrate (PAN), aldehydes, sulphuric acid, peroxides, etc. All these constitute photochemical smog, which retard photosynthesis in plants.

(ii) Causes of air pollution

(a) Agriculture : Hydrocarbons released by plants, pollen grains, insectisides etc. cause air pollution.

(b) Dust : Dust in the air is increased by dust storms wind, volcanoes, automobiles, etc.

(c) Industries : Combustion of fossil fuels like coal, petroleum, etc. Industrial smoke is the main source of pollution.

(d) Automobiles : The combustion of petrol and diesel in automobiles releases harmful gases into the air. They also produce dust.

(e) Ionising radiations : Ionizing radiations include alpha particles, beta particles and gamma rays. They are released into the air on testing atomic weapons.

(f) Freons : Use of freons and other chloro-fluoro-carbon compounds in refrigerants, coolants and as filling agents in aerosol also cause pollution.

(g) Aerosols : Aerosols are small particles of all sorts of solid or liquid substances suspended in the air. They block the stomata of plants and prevent the gaseous exchanges between plants and atmosphere. They may also change the climate of an area.

(iii) Biological Indicators : Some plants are sensitive to certain air pollutants. These plants are used to indicate the presence of these substances. These plants are called biological indicators. e.g.,

(a) The tissues present in the tip of dusheri mango turns black when they are exposed to sulphur dioxide \[(S{{O}_{2}})\] fumes.

(b) Pinto beans and Petunias are used to indicate the presence of peroxy acetyl nitrate (PAN).

(c) Tobacco and annual blue-grass plants are used to show the presence of ozone \[({{O}_{3}}).\] Lichens are biological indicaters of air pollution caused by \[S{{O}_{2}}.\]

(iv) Ecological effects of air pollution

(a) Death : When air is polluted with poisonous gases, death comes as a result immediately. Bhopal episode is a good example. Bhopal episode - On 2nd December 1984 about 3000 human beings died, due to the leakage of methyl isocyanate (toxic gas) into the air from an insecticide plant managed by Union Carbide Corporation.

(b) Chlorosis : The disappearance of chlorophyll is called chlorosis. It is caused by \[S{{O}_{2}},\] nitrogen dioxide, ozone and fluorides.

(c) Necrosis : The breakdown of cells is called necrosis. It is caused by \[S{{O}_{2}},\] nitrogen dioxide, ozone and fluorides.

(d) Green house effect : \[C{{O}_{2}}\] is released into the air by the combustion of fuels. It is estimated that \[C{{O}_{2}}\] content of the air is increasing at the rate of 0.4% per annum. This will result in an appreciable warming up of the earth. This is called green house effect.

(e) Crop losses : Heavy loss of crop is caused by smog. Smog denotes a combination of smoke and fog. The important components of smog are ozone and PAN (peroxy acetyl nitrate). They damage leafy vegetables, cereals, textile crops, ornamental plants, fruits and forest trees.

(f) Respiratory disorders : Excessive ethylene accelerates respiration causing premature senescence (old age) and abscission (accumulation of yellow fluid (pus) in the body). Aldehydes irritate nasal and respiratory tracts. Chlorine and phosgenes (carbonyl chloride) cause pulmonary oedema. Bronchitis is another bad effect of air pollution.

(g) Nausea : \[{{H}_{2}}S\]smells like rotten eggs and causes nausea.

(h) Vomiting : \[S{{O}_{2}}\] causes vomiting.

(i) Jaundice : Arsines induce RBC breakdown and jaundice.

(j) Oxygen carrying capacity : \[CO\] reduces \[{{O}_{2}}\] carrying capacity of RBC by its permanent combination with haemoglobin.

(k) Coughing : Coughing is induced by phosgenes (carbonyl chloride).

(l) Headache : \[S{{O}_{2}}\] causes headache.

(m) Cancer : Cancer is caused by air pollutants like ash, soot, smoke, chromium, nickel and radioactive elements.

(n) Mutation : Radioactive elements produce  mutation. Ozone produces chromosomal aberrations.

(o) Cardiac diseases : Cadmium causes high blood pressure and heart diseases.

(p) Pneumonia : Pneumonia is caused by breathing in too much of manganese particles.

(q) Depletion of Ozone umbrella : In the atmosphere, about 30 km above the surface of the earth, the ozone molecules \[({{O}_{3}})\] form an umbrella. It prevents the penetration of harmful ultra violet radiation from the sun and thus protects the life of the earth. It is now feared that there is danger of depletion of the ozone umbrella, which may occur by the use of freons and other CFC-compounds in refrigerants, coolants in domestric refrigenrators and cold storage facilities, and as filling agents in the form of plastics and in aerosol packages. On reaching the ozone umbrella, they destroy ozone molecules as a result of photochemical reactions. Over the past 16 years, the density of the ozone layer has been diminishing at an average rate of 3%. It is calculated that the depletion of ozone layer by 1% results in an increase in the incidence of skin cancer by 5% to 7%. A hole in \[{{O}_{3}}\] layer has been discovered in Antarctica.

(r) Acid rain : One of the major environmental issues facing human society at the national and international level is the problem of rain water having low pH. The rainwater is always slightly acidic as \[C{{O}_{2}}\] in the atmosphere gets dissolved in it. However during recent years, it has been noted a further lowering of pH of rain water often as low as 2.4. This lowering of pH is due to the dissolution of acids in the rain water. Precipitation of oxides of sulphur and nitrogen with rain is termed acid rain.  Acid rain is caused by air pollution. When atmospheric air contains sulphur dioxide \[(S{{O}_{2}})\] and oxides of nitrogen such as nitrous oxide \[({{N}_{2}}O)\] and nitric oxide (NO), they dissolve in rain water forming sulphuric acid and nitric acid. The rain water falls as acid rain.

Acid rain affects both materials and organisms. It attacks building materials principally sandstone, limestone, marble, steel and nickel. In plants, it leads to chlorosis (gradual yellowing in which the chlorophyll making mechanism is impeded) or depigmentation of leaves.

Acid rain increases the acidity of lakes and rivers. Vast tracts of forests and lakes in Europe and North America have been destroyed by acid rain. Acidity kills fish, bacteria and algae and the aquatic ecosystem collapses into sterility leaving a crystal clear but ultimately a dead lake.

(v) Control of air pollution 

(a) The emission of exhaust from automobiles can be reduced by devices such as positive crankcase ventilation valve and catalytic converter.

(b) Electrostatic precipitators can reduce smoke and dust from industries.

(c) Gaseous pollutants arising from industries can be removed by differential solubility of gases in water.

(d) A finepray of water is the device called scrubber can separate many gases like \[N{{H}_{3}},\,\,S{{O}_{2}},\] etc. from the emitted exhaust.

(e) Vehicles based on compressed natural gas (CNG) should be introduced.

(2) Water pollution : Water pollution is degradation of quality of water due to addition of substances (e.g., silt), chemicals (e.g., metals, inorganic and organic chemicals) or factors (e.g., heat) and deprivation that makes it a health hazard, unfit for human use, use by animals and industries as well as growth of aquatic biota. Water pollutants belong to three categories - biological, chemical and physical.

(i) Biological : Various pathogens, e.g., viruses, bacteria, protozoa, helminthes, algae.

(ii) Chemical : Organic wastes, organic biocides (e.g., DDT, BHC) and polychlorinated biphenyls (PCBs), inorganic chemicals like As, Pb, Cd, Ni, Hg, phosphates, nitrates, fluoride, etc.

(iii) Physical : Hot water, oil spills.

  • Water pollution is of both types natural and anthropogenic.

Natural water pollution : It is water pollution caused by natural processes of soil erosion and addition of clay or silt, run off and leaching.

Anthropogenic or Man-made pollution : It is water pollution caused by human activities like industrial effluents, domestic sewage, waste from animal sheds and slaughter houses, detergents, pesticides and fertilizers, oil spills, etc.

(i) Water pollutants : The common water pollutants are : Domestic sewage, Industrial effluents, Pesticides,  Herbicides, Fertilizers, Bacteria and Viruses, Plankton blooms and Heavy metals like Mercury, Temperature, Silt, Radioactivity, Oils etc.

(ii) Causes of water pollution 

(a) Domestic sewage : Domestic sewage consists of human faces, urine, and the dirty used–up water in houses. It contains a large number of bacteria and virus. The sewage is released into the rivers on the banks of which most of the cities are situated.

(b) Industrial effluents : All industrial plants produce some organic and inorganic chemical wastes. Those nonusable chemical are dumped in water as a means of getting rid of them. The industrial wastes include heavy metals (Hg, Cu, lead, zinc etc), Detergents, Petroleum, Acids, Alkalies, Phenols, Carbonates, Alcoholcyanides, Arsenic, Chlorine, etc.

(c) Thermal pollution : Hot effluents and hot water (e.g., thermal plants/atomic reactors) bring about rise in water temperature. Warm water contains less oxygen, has lower rate of putrescibility resulting in increased organic loading, replacement of green algae by blue-green ones. Many animals fail to reproduce e.g., Trout, Salmon.

(d) Run off from Agricultural fields : It is of three types – animal wastes, fertilizers and pesticides.

(e) Radioactive wastes : Liquid radioactive wastes are released into the sea around nuclear installations. The oceanic currents carry the radioactive contaminants every where.

(f) Oil pollution : Oil is a source of pollution in sea-water. Oil pollution is due to ship accidents, loading and discharging of oil at the harbour, oil refineries and off-shore oil production. Degree of impurity of water due to organic matter is measured in terms of BOD (Biochemical Oxygen Demand). It is the demand for \[{{O}_{2}}\] to decompose organic wastes in liter of water.

(g) Eutrophication : Rich growth of micro-organisms consumes most of the dissolved oxygen, so as to depreve other organisms. It generally occurs at the bottom layers of deep lakes. Addition of excessive plant nutrients intensifies eutrophication. It harmful to fish and other aquatic life.

(h) Ground water : Though a lot of filtration occurs before water reaches the underground water table, ground water does become polluted due to following reasons :

  • Underground sewage disposal pits.
  • Septic tanks.
  • Refuse dumps.
  • Industrial effluent dumps.
  • Leaching of pesticides and fertilizers.

(iii) Effect of water pollution

(a) Chemical pollutants

  • Many chemicals present in industrial effluents are poisonous causing various types of deformities, e.g., mercury (minamata disease), lead (plumbism), cadmium (itai-itai), nickel, arsenic, chromium, etc.
  • Some chemicals like acids contained in industrial effluents are corrosive. They damage water treatment plants.
  • Persistent pesticides enter food chains, undergo biomagnification and harm the aquatic life as well as land animals dependent on it.
  • Organic sulphur inhibits nitrification.

(b) Odour : Free chlorine, ammonia, hydrogen sulphide, phenols, growth of algae and microorganisms produce unpleasant odour.

(c) Turbidity : Water becomes muddy or turbid due to suspension of mineral dust, silt and related colloidal particles. Turbidity hinders penetration of light. It causes clogging of gills in fishes. Therefore, both plant and animal life is destroyed. Turbid water is also not suitable for drinking or industrial use.

(d) Colour : Dyes, iron and chromium compounds and anaerobic decomposition cause colouration of water, the coloured water is not suitable for recreational, drinking and industrial uses.

(e) Taste : It is impaired due to occurrence of pollutants like free chlorine, phenol, iron, manganese, detergents, hydrocarbons, oils and decomposition products.

(f) Foam : It develops over the surface of water due to mixing of detergents, soaps and alkalies. Foam makes the water unfit for various human uses.

(g) Oil pollution : It comes from spills of oil refineries, oil wells and washing of oil tankers. Oil spreads over water, kills plankton, neuston, necton, water birds and other organisms. Oil may also catch fire.

(h) Scum and Sludge : They are produce by organic wastes especially \[{{H}_{2}}S\] produced by them. The sulphide combines with metallic ions and form brownish or blackish substance that float over ad inside water.

(iv) Control of water pollution : Pollution control by sewage treatment includes the following steps :

(a) Sedimentation : When sewage is allowed to stand, the suspended particles settle to the bottom. So by sedimentation the suspended particles are removed from sewage.

(b) Dilution : The sewage can be diluted with water. This increases the \[{{O}_{2}}\] contents and reduces BOD and \[C{{O}_{2}}.\]

(c) Storage : The diluted sewage is stored in a pond. This facilitates the growth of micro-organisms. This renders further oxidation of sewage.

(d) Waste stabilization pond or Oxidation pond : Domestic and industrial wastes are stored in a dilute condition in shallow ponds called oxidation or stabilization ponds. After a few days micro-organisms and algae flourish. The micro–organisms decompose the organic wastes by oxidation, and the water is purified. This water is rich in nitrogen, phosphorus, potassium and other nutrients. This water can be used for fish culture, agriculture etc.

(e) Recycling : Pollution can be prevented to a certain extent by reutilizing the wastes. This is called recycling. e.g., :

  • The dung of cows and buffalo can be used for the production of energy (gobar gas).
  • Sewage can be used for irrigation and fish culture after treatment in oxidation pond. Certain pollutants from industrial effluents can be removed by filtration and selective absorption.

(3) Soil pollution or Land pollution : It is alteration in soil caused by removal or addition of substances and factors which decreases its productivity, quality of plants and ground water. It is of four types - negative pollution, positive pollution, third pollution and third poison.

Soil pollution is direct if the pollutants are passed over it directly e.g., industrial effluents, fertilizers. It is indirect if the pollutants reach soil from other resources like air and water, e.g., acid rain.

(i) Land pollutants : Manure, crop–residues, ashes, cinders (pieces of coal), garbage (waste food), paper, card board and plastics. Plastics are the most important land pollutants. Rubber, leather, cloth, rubbish, bricks, sand, metal, broken glasses, demolished building, dead animals, discarded furniture, automobiles, insecticides, herbicides and other biocides and radioactive elements are some of the important land pollutants. The main sources of land pollution are pesticides, radioactive elements and fertilizers.

(a) Pesticides : Pesticides are chemicals used to kill pests like insects, rats, snails, fungi, herbs, etc. They are collectively called biocides because they kill life.

Ecological effects of pesticides

  • Mutation : Insecticides induce gene mutation in human beings (Wurster, 1974).
  • Cancer : DDT produces cancer in human tissues.
  • Congenital birth defects : Certain herbicides like diozan increase birth defects in both people and livestock.
  • Sex hormones : DDT affects sex hormones in mammals and birds.
  • Decline of reproduction : In Bermuda petral, a sea bird, the rate of hatching of eggs is much reduced because of the accumulation of DDT. If the accumulation increases further, there will be failure of reproduction in this species in future.
  • Calcium metabolism : DDT interferes with calcium metabolism resulting in calcium deficiency. DDT causes hormonal disturbance resulting in delayed ovulation and inhibition of gonad development.
  • Biomagnification : The pesticides are non–degradable. They have much affinity towards fat. Hence they tend to move into the living organisms. They are concentrated as they pass up the food chains. For example, at each trophic level, the accumulation of insecticides increases by 10 times. For example if the goat gets one part per million (PPM) of DDT from the grasses, it will have 10 ppm in its tissues. The man, eating the goat will have 100 ppm. The man-eating tiger will have 1000 ppm. If the food chain is still greater, the accumulation will still be higher. This increasing accumulations of insecticides in higher organisms is called biomagnification or biological amplification. DDT causes the pollution of air, water and soil.

(b) Fertilizers : Excessive use causes soil deterioration through decrease of natural microflora. Leaching down causes pollution of underground water (third poison). Salts entering crop plants in excess may prove harmful.

  • It reduces soil microflora so that biogeochemical cycling and decomposition processes are disturbed.
  • It destroys crumb structure of soil.
  • It increases salt loading of soil causing salination.
  • A part of the fertilizer supply leaches downwardly into ground water.
  • Extra minerals bring about mineral enrichment of foliage crops. Extra nitrate is known to harm respiratory system because of the production of methaemoglobin which is unable to carry oxygen.

(c) Industrial wastes and chemicals : Industrial wastes and effluents are often dumped over soil. They contain several heavy metals like nickel, chromium, aluminium, tin, copper, zinc, cadmium, toxic chemicals like cyanides, acids and alkalies, dyes, organic solvents, etc. The chemicals become part of soil. They harmfully affect plant growth and soil biota. Both ground water and nearby water bodies are polluted through leaching and run-off.

(d) Mining wastes : They include mine dust, rock tailings, slack and slag. Open cast mining (surface dug out to bring out mineral deposit) completely spoil the surrounding soil. Toxic metals and chemicals present in the mining wastes destroys vegetation and produce many deformities in animals and human beings.

(e) Radionuclides : They are present in ores, coal, waste of mineral purification and uranium mines, etc. A lot of radio-isotopes are also used in research and medicine. Despite best precautions some radionuclides constantly enter soil and are transferred to food chain.

(f) Manures : They are prepared from garbage, sewage sludge and excreta of livestock. The manures carry a lot of pathogens. They contaminate soil and crops. From crops, the pathogens are transferred to domesticated animals and human beings.

(g) Discarded materials : Waste food, garbage, rubbish, glass, plastic and metallic waste articles are dumped over the soil, generally on the outskirts of urban areas. The soil gets polluted, contaminated and becomes breeding place of several pathogens.

(ii) Control of soil pollution

Soil pollution caused by solid wastes can be corrected by the following methods.

(a) Salvage : Articles which can be recycled should be removed from garbage, e.g., metals, glass, polythene, paper, rags, etc. It provides employment to rag pickers and helps in recycling of wastes.

(b) Construction material : Flyash is being converted into bricks for construction work. Flyash, industrial effluents containing toxic chemicals and hazardous metals can be used as bedding material for road construction.

(c) Dumping (Landfilling) : Dumping is piling of waste on selected low lying land. It is of two types, open and sanitary.

(d) Pyrolysis : The waste is heated anaerobically at a temperature of 1650°C. It yields industrial gas, alcohols and a number of other chemicals. The bulk of the waste is reduced. Residue is disposed off in land-fill.

(e) Burning : This is a common method for reducing bulk of wastes. Rubbish and garbage are commonly burnt in open spaces. It, however, releases offensive odour and smoke.

(f) Incineration : Waste is burnt aerobically at 900-1000°C. The hot gases and smoke are further passed into a chamber where the temperature is 1300°C. It burns the smoke particles. The gases released from the second chamber are taken to wet scrubber for removing suspended particles and soluble gases. Ash formed in incinerator is collected and disposed off in land filling.

(g) Recycling of wastes : Paper, glass, polythene and metals can be recycled. Though paper recycling is a bit costlier, it saves a lot of wood. For example one tonne of recycled paper saves 17 medium sized trees from felling. Recycling of metals not only saves the scarce resource but is also cheaper and less polluting.

(h) Agricultural wastes : Instead of burning or manuring them, they can used for preparation of industrial paper, cardboard, hardboard, poultry feeds, etc.

(i) Pesticides and Fertilizers : Their use should be reduced by resorting to biological control (for pests) and organic farming.

(j) Biogas plants : Cow dung, human excreta and putrescible garbage can be mixed and used for generation of biogas. Manure is produced as a by-product.

(k) Sludge : Sludge obtained from sewage treatment plants can be used in thermal power plants along with coal.

(4) Radioactive pollution : It is degradation of environment due to release of radioactivity (emission of \[\alpha -\]particles, \[\beta -\]particles and gamma rays) by changes in nuclides of unstable/radioactive elements causing short-range and long range harmful effects on living beings including humans. Radioactivity is measured in units called roentgens or r.

(i) Types of radiations

(a) Background radiation : It is radiation level found naturally in biosphere due to cosmic rays reaching earth and radio-nuclides found in earth's crust. Maximum background radiation is found in Kerala beach where 75% of thorium deposits of the world are found.

(b) Man-made radiations : They are due to mining and refining of radioactive elements like Plutonium, Uranium and Thorium, nuclear power plants and fuels, preparation of radio-active isotopes, production and explosion of nuclear weapons.

Nuclear weapons : Radiations are released during atmospheric testing of nuclear weapons and their actual use. Atmospheric testing of nuclear weapons has been banned because of release of destructive radiations. Nuclear weapons use uranium-235 and plutonium-239 for fission (atom bomb) and additional hydrogen or lithium for fusion (hydrogen bomb). A nuclear explosion gives rise to -

Radioactive gaseous matter rising up as a mushroom like cloud that disperses later on to spread radioactivity far and wide, polluting air, water and soil of all the places. Radioactivity passes into food chains and affects the whole biota.

Atomic reactors : They employ controlled radioactive fission fusion for liberation of energy.

  • The coolant water causes thermal pollution.
  • Small amount of radioactivity enters coolant water which undergoes biomagnification to some 75000 times in birds.
  • (vii) Mishaps do occur in nuclear reactors. One of the causes is core melting, e.g., Chernobyl in Ukraine (1986).

Radio-Isotopes : They are used in research (e.g., metabolic pathways, induction of mutations in plants and microorganisms, radiotherapy, etc.) e.g., \[Co-60,\text{ }P-32,\text{ }C-14,\text{ }I-125.\]

X-rays : They are employed for detecting diseases of lungs, heart, kidneys, joints and fractures. Repeated exposure to X-rays is harmful. Radiologists are prone to radiation disorders.

Other exposures : Workers engaged in radioactive mineral extraction, fuel processing, nuclear power plants, irradiation plants, etc. are always at risk of exposure to radiations.

This pollution occurs through radiations. Radiations are of two types.

  • Non ionising radiations : UV rays, IR rays, etc. UV rays cause skin burning, IR rays increases atmospheric temperature and leads to the green house effect.
  • Ionising radiation : \[X-\]rays, \[\beta -\]rays, \[\gamma -\]rays, \[x-\]rays cause genetic injury on mutation.

Types of ionizing radiations : Radioactive isotopes release three types of radiations :

  • Alpha particles : These are large particles emitted by radioactive isotopes (as\[{{U}^{238}}\]). They travel only short distances. They cannot penetrate the organisms. They cause ionization.
  • Beta particles : These are small particles emitted by radioactive isotopes. They can travel long distances. They can easily penetrate the body tissues and cause ionization.
  • Gamma rays : These are short wavelength rays emitted by radioactive isotopes. They can travel long distances. They can easily penetrate the body tissues and cause ionization. On the basis of the biological effects produced, the radioactive radiations can be grouped into two types, namely internal emitters and external emitters.

(ii) Harmful effects : They were first recorded in 1909 in uranium miners as skin burns and cancers. Many plants are killed even at low level of radioactivity. Young and recently divided cells are more easily damaged.

(a) Short range effects : Loss of nails and hair, subcutaneous bleeding, changed proportion of blood cells, changed metabolism, damaged to all organs death in high dose.

(b) Long Range/Delayed Effects : Tumours, cancers, mutations, genetic deformities, shorter life span.

(iii) Control of radiation pollution : There is no cure for radiation damage. Therefore, the only solution is prevention of radioactive pollution. The various methods are as follows :

(a) Leakages : Strict safety measures should be enforced to check leakage of radioactivity from reactors, reactor fuel during its handling and transport, radio-isotopes and radioactive wastes.

(b) Monitoring : A regular monitoring of radioactivity should be carried out in all risk areas.

(c) Accidents : All measures required to prevent occurrence of accidents should be followed.

(d) Waste disposal

Substances with very low radiation level can be discharged into municipal sewers.

  • Low activity wastes should be stored for some time as to reduce their activity further before final disposal.
  • Radionuclides should be separated through precipitation, coagulation or concentration. The concentrated wastes are then changed into glass, ceramic or concrete. This transforms the radioactive waste into non-absorbable and unleachable form. The locked waste is the put in concrete filled drums which are sealed and buried in sea at least 1000 fathoms deep.

(e) Safety norms : All safety norms should be strictly followed in copy book style by all workers. This includes wearing of protective dresses.

(5) Noise pollution : Noise is unwanted annoying sound of generally 80 dB and above. It is a physical non-persistent pollution which affects the receiver directly. Upto a certain limit, the effect depends upon the mood and upbringing of the person.

(i) Frequency : Frequency of sound is measured in cycles per second called Hertz or Hz. Human hearing lies within the frequency of \[5015,000\text{ }Hz.\] Below 50 Hz is infra sound while above 15,000 Hz is ultrasound. Infrasonic sound or infrasound waves cannot be listened but certain body parts resonate at this frequency. Therefore, they can be felt. Infrasound can damage the body parts. Ultrasonic vibrations or ultra sound waves are employed in imaging, cleaning, drilling, cutting, welding and sealing packages.

(ii) Loudness : Loudness or sound intensity is measured in decibels or dB.

(iii) Some boom : It is a series of shock waves left behind by a supersonic jet flying at a speed of more than one Mach (speed of sound). It produces sudden rattling of windows and doors. Buildings may develop cracks. Startle reaction may appear in human beings and animals.

(iv) Sources of noise pollution : Natural sources of noise pollution are rare (e.g., thunder of clouds). Man-made noise pollution is also a recent phenomenon. The important sources are as follows :

(a) Loud speakers

(b) Commercial establishments

(c) Builders

(d) Defence equipment

(e) Agricultural machines

(f) Industries

(g) Functions

(h) Crackers

(i) Transport vehicles

(j) Domestic gadgets

(v) Effects : Noise brings about :

(a) Damage to ear drum and impairment of hearing (a ten year exposure to 80 dB impairs hearing by 15 dB).

(b) Interference in conversation and hearing.

(c) Emotional disturbance, development of anxiety and stress (first effect).

(d) Damage to eye sight, colour perception, night vision, etc.

(e) Hypertension, changes in peripheral circulation and breathing pattern, decreased heart output and gastric problems.

(f) Startle reaction.

(g) Headache, sleeplessness, annoyance and irritability.

(h) Reduced productive performance.

(vi) Control of noise pollution : Noise pollution can be controlled through three methods :

(a) Reduction at source.

(b) Protection of receiver.

(c) Interruption in transmission.

The various methods of controlling noise pollution are as follows :

Sound absorption : The sound entering residential areas and dwelling units should be reduced. Acoustic furnishing should be undertaken to absorb sound and reduce noise pollution.

Sound diversion : High intensity sound should be deflected away from residential areas.

Quieter machines : Efforts should be made to develop quieter machines.

Loud speakers : Their use should be restricted. Under no condition the sound level be raised above 90 dB during the day and 60 dB during the night.

Occupational exposures : In case a person works in industry producing high intensity sound, ear plugs and ear muffs should be used for protection of ears.

Traffic : Highway traffic is not allowed to pass through towns and cities. It is diverted through by passes and over-bridges. Pressure horns are not allowed inside towns and cities.

Green muffler : \[45\]rows of trees and shrubs are grown along roads, rails, around industrial area and residential complexes in order to decrease the intensity of sound.

Noisy machines : They are isolated or kept inside sound proof chambers.

Maintenance of machines : Regular maintenance and lubrication of machines keeps the sound level low...


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