Air pollution and control

Kinds of Pollution

(a) On the basis of origin : It is of two types

(i) Natural Pollution : Pollution caused by natural phenomena like emission of large quantity of toxic gases and particulate matter by volcanoes, landslides, forest fires, marsh gas, U.V. rays etc.

(ii) Anthropogenic Pollution : It is man made pollution caused by human activities like noise, automobiles, pesticides, industries etc. Its magnitude is quite less as compared to Natural Pollution. Anthropogenic pollution can be personal (smoking), community level (thermal power plant) or occupational (flour mill dust). For example; 0.05% of atmospheric pollution is man made while 99.95% is natural pollution.

(b) On the basis of physical nature: It may be gaseous, dust, thermal, noise or radioactive pollution depending on physical nature of pollutants.

(c) On the basis of part of environment: Pollution may be broadly classified as air, water and soil pollution.

(d) On the basis of emission: Pollution is classified as :

(i) Point source: Pollution is being emitted from a single point or definite source. e.g. municipal sewer passing into water body.

(ii) Non point source: Pollution is being emitted from a large area. e.g., agricultural run off

(iii) Area source: Whole area like mining area is producing pollution. e.g., mining area, industrial complex.

Classification of Pollutants

1. Based upon their natural disposal, pollutants are of two types:

(i) Biodegradable pollutants: These are easily decomposable wastes by natural processes and also by some artificial methods which include microbial action and radiations. Domestic sewage is the main pollutant of this category.

(ii) Non-degradable pollutants: These are generally not degraded or degraded at a very slow pace by the natural biological processes. e.g., aluminium cans, mercurial salts, long chain phenolic chemicals, DDT, arsenic salts of heavy metals, glass, tin containers, radioactive materials and plastics. These not only accumulate but often get biologically magnified.

2. According to their existence in nature, the pollutants may be quantitative or qualitative.

(i) Qualitative pollutants: They are pollutants which do not normally occur in the environment but are passed into it through human activity e.g., DDT and other pesticides, fungicides, herbicides, etc.

(ii) Quantitative pollutants: They become pollutants only when their concentration reaches beyond a critical value in the environment e.g., CO, CO2, nitrogen oxides.

3. On the basis of form of pollutants in which these persist after their release into the environment, these are again of two types:

(i) Primary pollutants: These are emitted directly in the environment from some definite sources such as particles of metals, carbon, DDT, tar, resin, pollen, fungi, bacteria, silicates, plastics, sulphur compounds in the form of SO2, SO3, H2S; carbon compounds in the form of CO, CO2; nitrogen compounds (NOx).

(ii) Secondary pollutants: These are formed by the reactions of primary pollutants in the environment e.g., a photochemical reaction occurs in the presence of bright sunlight between nitrogen oxide and waste hydrocarbons to form peroxyacetyl nitrate (PAN), Ozone (O3) etc.

AIR OR ATMOSPHERIC POLLUTION

It is defined as occurrence or presence of any material or gas in the air in such a concentration which is harmful to man, vegetation, animals and their environment.

With the gradual increase in the number of industries and automobiles, air pollution has now reached menacing proportions in big cities and industrial centres.

I. Causes / sources of air pollution

Various sources of atmospheric pollution are as follows :

1. Fossil fuels and fibres: Incomplete and complete combustion of the carbon contents of fossil fuel wood and charcoal produce carbon monoxide and carbon dioxide alongwith sulphur dioxide.

2. Emission from vehicles : Emission from automobiles, locomotives, aircrafts and exhausts in cities constitutes the major part of the total air pollution.

3. Industries: Industries add various harmful gases like CO, CO2, SO2, H2S, NO, hydrocarbons and small particles of dust, carbon, metals, radioactive materials etc. to the atmosphere.

4. Natural sources: Volcanic eruptions, forest fires, natural organic and inorganic decays, marsh gases, pollen grains of flowers, fungal spores, etc.

5. Metallurgical processing

II. Common air pollutants and their effects

These are basically of two types i.e. gaseous materials, particulate matter.

1. Gaseous Materials :

(a) Carbon monooxide : It is a product of incomplete combustion of fossil fuels (charcoal, coal mines). 50% emissions are contributed from automobiles. It produces COHb (carboxyhemoglobin) and reduces O2 carrying capacity of blood, resulting in giddiness, decreased vision, headache, cardiovascular malfunction and asphyxia.

(b) Hydrocarbons (HCs) or Volatile organic carbons (VOCs) : They are produced naturally (e.g., CH4) or due to incomplete combustion as unburnt discharges. These may lead to produce secondary pollutants, when combines with NOx Benzene and HCHO are carcinogenic and causes irritation of eyes and mucous membrane and causes bronchial constriction. HCHO released from newly formed carpets lead to indoor pollution.

(c) SO2: It is produced during combustion of sulphur containing fossil fuels, smelting of ore and from oil refineries. It causes eye irritation, severe respiratory problems, inhibits ET8 in plants. Also responsible for classical smog (London smog or sulphurous smog) acid rains and stone cancer. SO2 causes phaeophytization in lichens. So their absence is indicator of SO2 pollution. This may cause discolouration and deterioration of buildings, sculptures (yellowning of Taj Mahal is reported to be caused by SO2 pollution released by Mathura oil refinery).

(d) Nitrogen oxides (NOx) : Mainly produced during combustion of fossil fuels at high temperature in automobile engines (mainly NO and NO2). Nitrogen oxides cause the brown air that leads to heart and lung problems.

Secondary Air Pollutants:

Formed through a reaction between primary pollutants and often are more toxic.

Oxides of nitrogen reacts with hydrocarbons in presence of sunlight to produce PAN and O3.

In trophosphere the O3 is a chemical weed and can cause eye irritations and sometimes prove fatal, while PAN can have damaging effect on eyes and may induce respiratory distress. It can inhibit ETS in chloroplast and may results in silvering or glazing of leaves.

Smog : Opaque or dark fog having smoke, dust, water vapours and gases.

Acid Rain

The term was given by Robert Augus.

It is rainfall with a pH of less than 5.65. It is due to oxides of sulphur and nitrogen.

There are two types of acid deposition -wet and dry deposition.

About half of the acidity in the atmosphere is transferred to earth through dry deposition.

65% acid rain is due to SO2 emission, 30% due to nitrogen oxides and 5% due to release of hydrogen chloride from chemical industries.

Acid rain damages foliage and growing points of plants and causes leaching of essential minerals of soil.

It corrodes metals, marble, painted surface, slate, stone etc.

This phenomenon is called stone leprosy.

2. Particulate Matter:

These are added into the air by industries automobiles and by many operations like blasting, drilling, crushing, grinding, mixing etc.

These pollutants may be either solid or liquid particles. It is differentiated into Settleable ( 10 µm, settles out in less than one day) and Suspended ( 10 µm) remaining in air for weeks.

Some particulate matters are given below:

(a) Aerosols. These are the vapour chemicals in the form of fluorocarbons, chlorofluorocarbons, oxides of sulphur and nitrogen released into the air with force by the emission of jet and supersonic aeroplane emissions. Fog is an aerosol of water droplets in air. Aerosols are also used as disinfectants, in refrigeration and in the formation of certain solid plastic foams.

(b) Smoke. Similar to dust but consists of visible suspension of carbon and other particles given off by burning and smouldering organic matter. Smog is a combination of smoke, chemical fumes and fog. It remains suspended for many days and envelops the entire industrial area like a thick blanket due to stagnant air. It produces respiratory problems in humans such as asthma and bronchitis. Smoke does not allow a clear view of nature's beauty. The power stations throw out large amount of fly ashes (fine particulate matter passed out alongwith gases during burning of coal).

(c) Dust and mist. Dust (more than 1µm), Mist (more than 1 µm but liquid). These releases from industries and may cause a variety of diseases like, cotton dust produces lung fibrosis called byssinosis. Lung fibrosis produced in other industries includes asbestosis (in asbestos industry), silicosis (stone grinders), siderosis (iron mill), coal miners pneumoconiosis, flour mill pneumoconiosis etc. Manganese poisoning has been reported in welders.

(d) Pollen, spores, cysts and bacteria. Air borne organic constituent like pollens, spores, cysts, fungi, bacteria, fur, etc. may cause allergic reactions, bronchial asthma, emphysema, T.B. and lung cancer. The number increases in certain seasons. Skin allergy and asthma like diseases are very common from Parthenium plant in India. The hay fever from pollen allergy is very common.

III. Control of air pollution

1. Separation of pollutants from harmless gases

(i) Control equipments in industries such as gravity settling tanks, cyclone collectors, remove and precipitate large and small pollutant particles and thus, minimise the air pollution. Electrostatic precipitators are used in thermal power plants. These can remove over 99% particulate matter present in the exhaust from a thermal power plant.

Fig. : (A) Scrubber; (B) Electrostatic preCipitator

It has electrode wires that are maintained at several thousand volts, which produce a corona that releases electrons.

These electrons attach to dust particles giving them a net negative charge.

The collecting plates are grounded and attract the charged dust particles.

The velocity of air between the plates must be low enough to allow the dust to fall.

A scrubber can remove gases like sulphur dioxide.

In a scrubber, the exhaust is passed through a spray of water or lime.

Recently we have realised the dangers of particulate matter that are very very small and are not removed by these precipitators.

According to Central Pollution Control Board (CPCB), particulate size 2.5 micrometers or less in diameter are responsible for causing the greatest harm to human health.

These fine particulates can be inhaled deep into the lungs and can cause breathing and respiratory symptoms, irritation, inflammations and damage to the lungs and premature deaths.

Catalytic converter have expensive metals, namely platinum, palladium, rhodium and can convert NOx to nitrogen and CO to CO2.

(ii) Controlling Vehicular Air Pollution -A Case Study of Delhi :

(a) Delhi leads the country in its levels of air-pollution -it has more cars than the states of Gujarat and West Bengal put together. In the 1990s, Delhi ranked fourth among the 41 most polluted cities of the world. Air pollution problems in Delhi became so serious that a public interest litigation (PIL) was filed in the Supreme Court of India. After being censured, the government was asked to take, within a specified time period, appropriate measures, including switching over the entire fleet of public transport, i.e., buses, from diesel to compressed natural gas (CNG). All the buses of Delhi were converted to run on CNG by the end of 2002.

Advantages of CNG

1. CNG burns most efficiently.

2. CNG is cheaper than petrol or diesel.

3. Cannot be siphoned off by thieves and adulterated like petrol or diesel.

4. The main problem that government has faced is the difficulty of laying down pipelines to deliver CNG through distribution points/pumps and ensuring uninterrupted supply.

Use of unleaded petrol, use of low-sulphur petrol and diesel, use of catalytic converters in vehicles, application of stringent pollution-level norms for vehicles, etc. are other steps taken to reduce pollution in Delhi.

(b) Stringent norms for fuels were given in new auto fuel policy for steadily reducing the sulphur and aromatic contents in petrol and diesel fuels. Euro-II norms, for example, stipulates that sulphur be controlled at 350 parts-per-million (ppm) in diesel and 150 ppm in petrol. Aromatic hydrocarbons are to be contained at 42 per cent of the concerned fuel. The goal, according to the road map prepared by Indian Government, is to reduce sulphur to 50 ppm in petrol and diesel and bring down the level to 35 per cent. Vehicle engines will also need to be upgraded.

(c) The Bharat Stage II (equivalent to Euro-II norms), which is currently in place in Delhi, Mumbai, Kolkata, Chennai, Bangalore, Hyderabad, Ahmedabad, Pune, Surat, Kanpur and Agra, will be applicable to all automobiles throughout the country from April 1, 2005. All automobiles and fuelpetrol and diesel -were to have met the Euro-III emission specifications in these 11 cities from April 1, 2005 and have to meet the Euro-IV norms by April 1, 2010. The rest of the country will have Euro-III emission norm compliant automobiles and fuels by 2010.

(d) A substantial fall in CO2 and S02 level has been found in Delhi between 1997 and 2005.

(iii) Height of chimneys in industries should be increased to the highest possible level to reduce smoke pollution at ground level.

(iv) Trees purify the air by consuming CO2 and releasing oxygen. Trees should be grown in all available places. Certain plants like Phaseolus vulgaris, Coleus blumei, Daucus carota and Ficus variegata fix carbon monoxide of the air. Similarly Vilis, Pinus, Juniperus, Pyrus, and Robinia pseudoacacia etc. are capable of metabolising oxides of nitrogen and other gaseous pollutants. These plants certainly help in reducing air pollution to a great extent.

2. Avoidance of Air Pollutants

(a) Industries should be set up at a far off distance from residential areas.

(b) Air pollution boards should enforce emission standards, frame rules and regulation for the control of air pollution.

(c) Firewood, coal and oil should be completely replaced by nuclear power, solar power, tidal power, wind power, natural gas or electricity which do not emit oxides of carbon, sulphur or nitrogen in the air.

(d) Automobile use should be minimised which emits high amount of air pollutants.

(e) Human population growth should be checked which is the major cause of air pollution.

Water pollution and control

WATER POLLUTION

Water pollution may be defined as any adverse change in composition and condition of the water which tend to lower its quality and cause health hazard or makes it unfit for domestic use.

I. Sources and effects of water pollution

(i) Sewage and domestic wastes.

Nearly 75% of water pollution is due to sewage and domestic wastes.

A mere 0.1 % impurities make domestic sewage unfit for human use (Fig.).

Sewage generally includes biodegradable pollutants like human faecal matter, animal wastes and many dissolved organic compounds e.g., carbohydrates, proteins, fats, urea etc. inorganic salts such as nitrates and phosphates of detergents.

These pollutants under natural processes are rapidly decomposed.

In water, organic wastes provide nutrition for many decomposers like bacteria.

These break down the organic part by using bulk of oxygen and deficiency of oxygen (reduced DO) kills the fishes and other aquatic animals.

Anaerobic bacteria in oxygen deficient water disrupt food chains.

Anaerobic bacteria produce foul smelling gases. These give rise to many other pollutants like H2S, NH3, organic sulphides, methane etc.

These make the water brownish and turbid.

Pollution strength is characterized by its Biochemical oxygen demand (BOD).

BOD is defined as the amount of oxygen (mg) consumed by microbiological action when 1000 ml sample of water containing known amount of oxygen is incubated for 5 days at 20°C in the dark.

A high BOD indicates intense level of biodegradable pollutants.

Water having DO content below 8.0 mg/L is considered as polluted. Heavily polluted waters have DO content below 4.0 mg/L.

Fig. : Effect of sewage discharge on some important characteristics of a river

COD (chemical oxygen demand) indicates total O2 requirement by all the O2 consuming pollutant materials (organic and chemical compounds) present in water.

Its value is higher than BOD. Annelid worm Tubifex and some insect larvae act as indicator species for polluted waters.

(ii) Industrial wastes and effluents.

The industrial wastes and their effluents include poisonous materials like acids, alkalies, chromium salts, phenols, cyanides, insecticides, agricultural chemicals, chlorine, ammonia, hydrogen sulphides, salts of heavy metals such as of copper, lead, zinc and mercury.

The water becomes toxic and deoxygenated, so this cannot support aquatic life.

Mercury enters the food chain, kills fish and poisons the remaining fauna, mercury cause minamata disease.

People feeding on these aquatic forms develop numbness of limbs and lips, impairment in speech hearing and vision, meningitis and genetic disorders.

Oils deplete oxygen of water, inhibit plankton growth and photosynthesis.

Sea birds smeared with oil fall sick and die.

Organic phosphates and nitrates enhance growth of algal blooms.

Black foot disease is caused by chronic exposure to arsenic.

(iii) Insecticides and pesticides.

Insecticides are biologically active chemicals are used for pest control.

These include D.D.T., S.H.C., copper sulphate and aldrin etc.

Aquatic microorganisms absorb them in fats and oils.

Fish feeding on these zooplanktons and phytoplanktons further concentrate these pesticides in their tissues.

Birds feeding on these fish concentrate these pesticides still more.

The increased accumulation of these toxic substances in the food chain at higher trophic level is called biological magnification.

Many species of predatory birds like eagles, cormorants, hawks have shown serious adverse effects from this accumulation.

Thinning of egg shells is the major effect.

The degree of magnification of insecticides is generally proportional to their persistence and inversely related to their solubility in water.

(iv) Detergents and fertilizers.

Detergents are washing materials in water which cause soapiness.

These form a film around organic waste.

Some of the fertilizers such as nitrates and phosphates are used in agriculture to increase the crops yield reach through irrigation, rainfall and drainage into rivers and ponds where they seriously disturb the aquatic ecosystem.

When such waters are used by animals, the nitrates of polluted water become reduced to toxic nitrites in their body by intestinal bacteria.

The nitrites in the body combine with haemoglobin to cause a serious disease called methaeglobinemia or Blue baby syndrome.

It reduces the oxygen carrying capacity of the blood.

It damages respiratory and vascular systems and sometimes causes suffocation.

Eutrophication The natural aging of a lake by biological enrichment of its water.

In a young lake the water is cold and clear, supporting little life.

With time, streams draining into the lake introduce nutrients such as nitrogen and phosphorus, which encourage the growth of aquatic organisms.

As the lake's fertility increases, plant and animal life burgeons, and organic remains begin to be deposited on the lake bottom.

Over the centuries, as silt and organic debris pile up, the lake grows shallower and warmer, with warm-water organisms supplanting those that thrive in a cold environment.

Marsh plants take root in the shallows and begin to fill in the original lake basin.

Eventually, the lake gives way to large masses of floating plants (bog), finally converting into land.

Pollutants from man's activities like effluents from the industries and homes can radically accelerate the aging process.

This phenomenon has been called Cultural or Accelerated Eutrophication.

Eichhomia crassipes grow abundantly in eutrophic water body.

(v) Siltation.

Excessive agricultural and forestry practices cause soil erosion (removal of top fertile soil) during heavy rain.

The water becomes muddy which fails to support much plant growth due to poor light.

(vi) Thermal pollution.

Heated waste water from power plants and industries, which raises the temperature of water to a harmful level is called thermal pollution.

Thermal pollution speeds up the biodegradation of organic matter which results into ecological imbalance of the rivers and streams.

Warm water holds less oxygen as heat causes deoxygenation in water.

It increases the rate of metabolism and microbial activity.

Many fish and other aquatic animals which are sensitive to temperature changes in water cannot withstand and die.

II. A Case Study of Integrated Waste Water Treatment

Waste water including sewage can be treated in an integrated manner. An example of such an initiative is the town of Arcata (California).

The townspeople created an integrated waste water treatment process within a natural system in collaboration with Humboldt State University.

The cleaning occurs in two stages:

(a) The conventional sedimentation, filtering and chlorine treatments are given. After this stage, but dissolved heavy metals still remain.

(b) The biologists developed a series of six connected marshes over 60 hectares of marshland. Appropriate organisms were seeded into this area, which neutralise, absorb and assimilate the pollutants. Hence, as the water flows through the marshes, it gets purified naturally, marshes also constitute a sanctuary.

Friends of the Arcata Marsh (FOAM) are responsible for the upkeep and safeguarding of this wonderful project.

Ecological sanitation is a sustainable system for handling human excreta, using dry composting toilets. This is a practical, hygienic, efficient and cost-effective solution by which human excreta can be recycled into a resource (as natural fertiliser), which reduces the need for chemical fertilisers. There are working 'EcoSan' toilets in many areas of Kerala and Sri Lanka.

Solid wastes

 Soil pollutants and their effects

Agrochemicals-pesticides and weedicides :

A number of chemicals have been developed to kill a variety of pests in order to improve agriculture, forestry, horticulture and water reservoirs.

The most widely used among them are insecticides.

Most of these insecticides are broad spectrum and affect other animals, man and even plants.

They are, hence, also called biocides.

These include:

(i) Organo insecticides: They include DDT, PCB, Aldrin, BHC (benzene hexachloride) etc. Chlorinated hydrocarbons are toxic. Besides being toxic, these pesticides are both persistent and mobile in the ecosystem. The chlorinated hydrocarbons like DDT results in biological magnification.

Organophosphorus compounds (e.g., malathion, parathion) and organocarbamates are degradable but they influence the nervous system.

(ii) Weedicides (Herbicides) : The weedicides or herbicides are usually metabolic inhibitors which stop photosynthesis and other metabolic activities and hence kill the plants.

2. Industrial wastes:

Both solid and liquid wastes of the industry are dumped over the soil.

The wastes contain a number of toxic chemicals like mercury, copper, zinc, lead, cadmium, cyanides, thiocyanates, chromates, acids, alkalies, organic solvents etc.

3. Mine dust:

It is a major source of poilution in mining areas.

Mine dust not only spreads with wind but also spread over a large area during transportation to purification plants.

4. Fertilizers:

Excessive use of chemical fertilizers causes soil deterioration through the decrease in natural bacterial population (nitrogen fixing, nitrifying, etc.) and destruction of crumb structure.

The salt content of the soil is also bound to increase with continuous use of fertilizers.

Case Study of Organic Farming

Integrated organic farming is a cyclical, zero-waste procedure, where waste products from one process are cycled as nutrients for other processes.

This allows the maximum utilisation of resources and increases the efficiency of production.

Ramesh Chandra Dagar, a farmer in Sonipat, Haryana, is doing just this. He includes bee-keeping, dairy management, water harvesting, composting and agriculture in a chain of processes, which support each other and allow an extremely economical and sustainable venture.

There is no need to use chemical fertilisers for crops, as cattle excreta (dung) are used as manure.

Crop waste is used to create compost, which can be used as a natural fertiliser or can be used to generate natural gas for satisfying the energy needs of the farm.

Enthusiastic about spreading information and help on the practice of integrated organic farming, Dagar has created the Haryana Kisan Welfare Club, with a current membership of 5000 farmers.

Agro-chemicals and their effects

Agrochemicals-pesticides and weedicides :

A number of chemicals have been developed to kill a variety of pests in order to improve agriculture, forestry, horticulture and water reservoirs.

The most widely used among them are insecticides.

Most of these insecticides are broad spectrum and affect other animals, man and even plants.

They are, hence, also called biocides.

These include:

(i) Organo insecticides: They include DDT, PCB, Aldrin, BHC (benzene hexachloride) etc. Chlorinated hydrocarbons are toxic. Besides being toxic, these pesticides are both persistent and mobile in the ecosystem. The chlorinated hydrocarbons like DDT results in biological magnification.

Organophosphorus compounds (e.g., malathion, parathion) and organocarbamates are degradable but they influence the nervous system.

(ii) Weedicides (Herbicides) : The weedicides or herbicides are usually metabolic inhibitors which stop photosynthesis and other metabolic activities and hence kill the plants.

2. Industrial wastes:

Both solid and liquid wastes of the industry are dumped over the soil.

The wastes contain a number of toxic chemicals like mercury, copper, zinc, lead, cadmium, cyanides, thiocyanates, chromates, acids, alkalies, organic solvents etc.

3. Mine dust:

It is a major source of poilution in mining areas.

Mine dust not only spreads with wind but also spread over a large area during transportation to purification plants.

4. Fertilizers:

Excessive use of chemical fertilizers causes soil deterioration through the decrease in natural bacterial population (nitrogen fixing, nitrifying, etc.) and destruction of crumb structure.

The salt content of the soil is also bound to increase with continuous use of fertilizers.

Case Study of Organic Farming

Integrated organic farming is a cyclical, zero-waste procedure, where waste products from one process are cycled as nutrients for other processes.

This allows the maximum utilisation of resources and increases the efficiency of production.

Ramesh Chandra Dagar, a farmer in Sonipat, Haryana, is doing just this. He includes bee-keeping, dairy management, water harvesting, composting and agriculture in a chain of processes, which support each other and allow an extremely economical and sustainable venture.

There is no need to use chemical fertilisers for crops, as cattle excreta (dung) are used as manure.

Crop waste is used to create compost, which can be used as a natural fertiliser or can be used to generate natural gas for satisfying the energy needs of the farm.

Enthusiastic about spreading information and help on the practice of integrated organic farming, Dagar has created the Haryana Kisan Welfare Club, with a current membership of 5000 farmers.

SOLID WASTE

Solid wastes refer to everything that goes out in trash.

Sanitary landfills were adopted as the substitute for open-burning dumps where in a sanitary landfill, wastes are dumped in a depression or trench after compaction, and covered with dirt everyday.

But these sites are getting filled too and seepage of chemicals, etc., from these landfills pollutes underground water resources.

Anthropogenic solid waste is categorised into three types -(a) bio-degradable, (b) recyclable and (c) the non-biodegradable.

Polyblend, a fine powder of recycled modified plastic, was developed by the company owned by Ahmed Khan in Bangalore.

This mixture is mixed with the bitumen that is used to lay roads.

Blends of Polyblend and bitumen, when used to lay roads, enhanced the bitumen's water repellant properties, and helped to increase road life by a factor of three.

The use of incinerators (burning in presence of O2 at 900-1200°C) other is pyrolysis (anaerobic burning at 16S0°C) is crucial for disposal of hospital waste.

Irreparable computers and other electronic goods are known as electronic wastes (e-wastes). E-wastes are buried in landfills or incinerated.

Over half of the e-wastes generated in the developed world are exported.

Recycling is the only solution for the treatment of e-wastes, provided it is carried out in an environment-friendly manner.

Developing countries like China, India and Pakistan imports over half of the e-waste generated by developed countries for recovery of metals like copper, iron, silicon, nickel and gold.

RADIOACTIVE WASTES

It is physical pollution of air, water and soil with radioactive materials.

Radioactivity is the property of certain elements (radium, thorium, uranium etc.) to spontaneously emit protons (alpha particles), electrons (beta particles) and gamma rays (electromagnetic waves of very short wavelength) by disintegration of their atomic nuclei.

The elements that give radiation are called radioactive elements.

The use of nuclear energy has two very serious inherent problems.

The first is accidental leakage, as occurred in the Three Mile Island and Chernobyl incidents and the second is safe disposal of radioactive wastes.

It causes mutations to occur at a very high rate.

At high doses, nuclear radiation is lethal and at lower doses, it creates various disorders, the most frequent of all being cancer.

It has been recommended that storage of nuclear waste, after sufficient pre-treatment, should be done in suitably shielded containers buried within the rocks, about 500 m deep below the earth's surface.

Production of nuclear weapons involves the tests of nuclear arms.

These tests produce large amount radioactive elements into the environment and make other materials also radioactive. They include strontium-90, cesium-137, iodine-131 and some others.

The radioactive materials are transformed into gases and fine particles which are carried to distant places by wind.

When rain drops, the radioactive particles fall on the ground, it is called fall out.

Strontium-90 accumulates in the bones, replaces calcium and may cause bone cancer and tissue degeneration in most animals and man.

The operation of a nuclear power plant releases large amounts of energy.

This energy is used in large turbines, which produce electricity.

Wastes from atomic reactors also contain radioactive materials.

The biggest problem is the disposal of these radioactive wastes.

If these wastes are not properly disposed off, can harm the living organisms wherever they may be dumped.

NOISE POLLUTION

The quality of our environment is judged, apart from other factors, by the amount of noise present.

Noise has been defined as "unwanted sounds" which is being "dumped" into the atmosphere to disturb the unwilling ears.

It adversely affects our physiological and mental health.

Noise is measured by a sound meter and is expressed in a unit called decibel (dB).

Any value more than 80 dB causes noise pollution.

Noise becomes unbearable at 140 dB.

The quietest sound that man's ear can detect is known as threshold of hearing.

A noise that hurts one's ears and gives headache is called threshold of pain.

The role of sound vibrations is measured in cycles per second (cps) or hertz (Hz).

The ear is potentially liable to damage, if it receives high intensity noise.

Noise in general is a physical form of pollution.

It has no persistent adverse effects on the life supporting systems but, has direct effects on the recipients.

Moderate conversation = 60 dB

Loud conversation = 70 dB

Scooter = 80 dB

Truck / Bus = 90 dB

Jet aeroplane = 150 dB

Rocket = 180 dB

Zone-wise permissible ambient noise levels (acoustic zoning) are given below. (According to central pollution control board)

I. Sources of Noise Pollution

Noise can either be natural like thundering sound or man made. The main sources of man made noise pollution are:

(i) Annoying and damaging sounds of various industries.

(ii) Defence material like rockets, tanks etc.

(iii) Entertainment sources like record players, radios, cassette players, loud speakers etc.

(iv) Transport automobiles and other vehicles such as trucks, buses etc.

II. Effects of Noise Pollution

Noise causes some serious damaging effects which are briefed as follows :

(i) Diminish hearing. Noise damages the ears, causes temporary or permanent noise induced hearing loss, depending upon the intensity and duration of the noise level. It leads to auditory fatigue and may finally lead to deafness. A sudden loud noise of any explosion may damage the tympanic membrane permanently. Sudden noise is more harmful than the continuous one. Factory workers suffer chronic hearing loss after many years of occupational noise exposure.

(ii) It has adverse effects on thinking and coordination of limbs.

(iii) Noise affects verbal communication on which we depend in all kinds of environment.

(iv) Noise increases blood cholesterol level, causes high B.P., digestive spasm, decreased heart output, defective night and colour vision. It impairs the development of nervous system of unborn babies which leads to abnormal behaviour in later life.

Control of Noise Pollution

Noise pollution can be controlled by following measures :

(i) Green muflur scheme. Trees such as Neem and Ashoka absorb sound vibrations to a great extent. Plantation of these trees on both sides of the roads, around silent zones reduces the menace of noise pollution.

(ii) Sound absorbing material should be used for reducing industrial noise.

(iii) Noise producing agencies should be located far away from residential areas. Vehicular traffic should be directed away from the human dwellings, educational institutions and hospitals etc.

(iv) General awareness should be developed among the people to minimize noise pollution in the environment.

GLOBAL ENVIRONMENT CHANGE

CO2, CH4, N2O and CFCs are radiatively active gases and also called green house gases.

The increased amounts of these gases in atmosphere is affecting the global climate and this phenomenon is known as global climatic change.

I. Green House Gases and Global Warming

(i) Term green house effect was coined by Arrhenius.

(ii) Green house gases trap the long wave radiations. A part of this energy is re-radiated back to the surface of earth. The downward flux of long wave radiation by green house gases is called green house flux.

(iii) The phenomenon of keeping the earth warm due to presence of certain radiatively active gases in the atmosphere is called green house effect, without which the average temperature of earth would have been between -18°C to -20°C rather than present average of 15°C.

Relative contribution of different green house gases to global warming

(iv) The excessive increase in concentrations of these gases in the atmosphere would retain more and more of the IR -radiation (long wave radiations), resulting in enhanced green house effect.

(v) CFC is most effective green house gas (effectiveness is 14,000 times more than CO2),

Effects of Green House Gases

(a) CO2 fertilization effect: Increase in atmospheric concentration of CO2 increases productivity of C3 plants and decreases rate of transpiration due to partial stomatal closure.

(b) Possible Effects of Global Warming

(i) Increasing of global temperature (increased 0.6°C, most of it during last 3 decades) and more extreme climatic conditions [EI Nino effect].

(ii) Warming of troposphere and cooling of stratosphere and thermosphere.

(iii) Global warming will push tropics into temperate areas and temperate areas towards pole (shifting of climatic zones) and higher altitudes in mountains resulting into changed species distribution.

(iv) Melting of ice caps.

(v) Rising of sea level, changes in rainfall pattern.

Control measures -Reduced deforestation, cutting down use of fossil fuel, planting trees, slowing down population growth.

II. Ozone Depletion

(i) Ozone layer is present in stratosphere at altitude of 23-25 km (conc. 0.3 ppm) and act as shield against UV radiation.

(ii) Large hole has appeared in ozone shield over Antarctica and smaller one over North pole. (Discovered by Farman 1985).

(iii) Ozone is commonly called as chemical weed, 'Bad' ozone is formed in troposphere that harms plants and animals. Good ozone is found in stratosphere as shield.

(iv) ODS: ozone depleting substances -CFC, CH4, CCl4, halons and N2O causes destruction of O3.

(v) CFC's are most damaging. They release Cl free radicals in stratosphere which destroy O3.

(vi) Thinning of the ozone-layer results in an increase in the UV-B radiation.

(vii) UV -B damages DNA and mutation may occur. It causes aging of skin, damage to skin cells and various types of skin cancers. A high dose of UV-B causes inflammation of cornea called snow blindness.

(viii) Nowadays CFC's are being replaced by Hydro Fluoro Carbons (HFCs).

DEGRADATION BY IMPROPER RESOURCE UTILISATION AND MAINTENANCE

The lowering of quality, fertility and productivity of land by various factors such as salination of soil, soil erosion, desertification, shifting cultivation and developmental activities etc. is called land degradation. It is caused by five main factors :

(i) Developmental activities:

Many developmental activities such as rapid urbanisation, human settlement, mining, construction of roads, dams, canals, railways, airports, playgrounds, industries cause loss of large areas of fertile and productive land.

(ii) Soil erosion:

It is the removal of top, fertile, mineral rich soil layer by water, floods, wind, ocean waves, glaciers, felling of trees, overgrazing on slopes or some arid soils, over cropping and improper farming techniques etc. It occurs in both wet and arid regions. Roots of grasses are excellent binding material and keep the soil intact and free from soil erosion.

(iii) Desertification:

It is the change of fertile soil into a non productive desert soil. It is due to the shifting of sand dunes by strong winds, or by deforestation, soil erosion or overgrazing in lands sparsely covered by grasses. Many deserts in the world are man-made. Afforestation is the only solution to prevent desertification.

(iv) Shifting cultivation:

In many tribal communities of tropical and subtropical regions of Africa and Asia, it is a practice of slashing, cutting down trees, burning the felled trees and raising crops on the ash formed. This practice is called 'Jhum Cultivation' in north east India. This destroys forests and causes soil erosion.

(v) Salination of Soil:

Increase in the concentration of soluble salts in the soil is called salination. Origin or development of saline soil depends upon following factors:

(a) Poor Drainage of Soil: Salts dissolved in irrigation water accumulate on the soil surface due to inadequate drainage especially during flood.

(b) Quality of Irrigation Water: The ground water of arid (dry, barren having not enough rainfall to support vegetation) regions are generally saline in nature. The irrigation water may be itself rich in soluble salts and add to salinity of soils.

(c) Excessive use of basic fertilizers: Excessive use of alkaline fertilizers like sodium nitrate, basic slag, etc may develop alkalinity in soil.

(d) Saline nature of parent rock materials: If soil develops from saline nature of parent rock materials, soil would be saline.

Control of degradation : Degradation can be checked by the following measures :

(i) Reforestation and plantation of grassess can check soil erosion, floods and water logging.

(ii) Crop rotation and mixed cropping improve fertility. It would increase production, which would support large population.

(iii) Salinity of the soil can be checked by providing adequate drainage.

(iv) Desertification can be checked by artificial bunds or covering the area with suitable soil binding vegetation.

DEFORESTATION

It is the conversion of forested areas to non-forested ones. It is estimated that almost 40 per cent forests have been lost in the tropics, compared to only 1 per cent in the temperate region.

At the beginning of the twentieth century, forests covered about 30 per cent of the land of India. By the end of the century, it shrunk to 19.4 per cent, whereas the National Forest Policy (1988) of India has recommended 33 per cent forest cover for the plains and 67 per cent for the hills.

Trees are axed for timber, firewood, cattle ranching and for several other purposes. Slash and burn agriculture, has also contributed to deforestation.

One of the major effects of deforestation is increased carbon dioxide concentration in the atmosphere. It also causes loss of biodiversity due to habitat destruction, disturbs hydrologic cycle, causes soil erosion, and may lead to desertification in extreme cases.

Reforestation is the process of restoring a forest it may also occur naturally in a deforested area.

Case Study of People's Participation in Conservation of Forests

A Bishnoi woman of Khejarli village, Jodhpur, Rajasthan named Amrita Devi showed exemplary courage by hugging a tree.

Amrita Devi Bishnoi Wildlife Protection Award - for individuals or communities from rural areas that have shown extraordinary courage and dedication in protecting wildlife.

Chipko Movement. It is movement which was initially meant for protecting trees but not meant for preservation of environment including habitat and wildlife. Chipko movement was born in March 1974 in Gopeshwar in Chamoli district. The movement has two leaders, Chandi Prasad Bhatt of Gopeshwar and Sunder Lal Bahugana of Silyara in Tehri region. A similar movement was undertaken by Paudurang Hedge in the South. It is known as appiko movement.

Government of India in 1980s has introduced the concept of Joint Forest Management (JFM) so as to work closely with the local communities for protecting and managing forests.

ENVIRONMENTAL LAWS FOR CONTROLLING POLLUTION

Important legislations directed at the protection of environment in India are listed below:

(i) The Environment (Protection) Act, 1986

(ii) The Insecticide Act, 1968

(iii) The Water (Prevention and Control of Pollution) Act, 1974

(iv) The Air (Prevention and Control of Pollution) Act, 1981 (Amended in 1987 to include noise as an air pollutant.)

International Initiatives for Mitigating Global Change

The long-term challenge of stabilising the atmospheric concentrations of greenhouse gases requires that global emissions be significantly lowered than what they are today.

In 1987, many countries signed the Montreal Protocol (effective in 1989) at Montreal (Canada), a landmark international agreement to protect the stratospheric ozone by agreeing to limit the production and use of ozone-depleting substances, phasing out of ozone-depleting substances and helping the developing countries to implement use of alternatives to CFCs.

The United Nations Conference on Environment and Development (UNCED, Earth Summit), held at Rio de Janeiro, Brazil in 1992, established the principles for reducing greenhouse gas emission.

The Kyoto Protocol, approved by a follow-up conference held in Kyoto, Japan, during December 1997, has specified the commitments of different countries to mitigate climate change.

This protocol requires countries to take appropriate measures to reduce their overall greenhouse gas emissions to a level at least 5% below the 1990 level by the commitment period 2008-2012.

Radioactive wastes

RADIOACTIVE WASTES

It is physical pollution of air, water and soil with radioactive materials.

Radioactivity is the property of certain elements (radium, thorium, uranium etc.) to spontaneously emit protons (alpha particles), electrons (beta particles) and gamma rays (electromagnetic waves of very short wavelength) by disintegration of their atomic nuclei.

The elements that give radiation are called radioactive elements.

The use of nuclear energy has two very serious inherent problems.

The first is accidental leakage, as occurred in the Three Mile Island and Chernobyl incidents and the second is safe disposal of radioactive wastes.

It causes mutations to occur at a very high rate.

At high doses, nuclear radiation is lethal and at lower doses, it creates various disorders, the most frequent of all being cancer.

It has been recommended that storage of nuclear waste, after sufficient pre-treatment, should be done in suitably shielded containers buried within the rocks, about 500 m deep below the earth's surface.

Production of nuclear weapons involves the tests of nuclear arms.

These tests produce large amount radioactive elements into the environment and make other materials also radioactive. They include strontium-90, cesium-137, iodine-131 and some others.

The radioactive materials are transformed into gases and fine particles which are carried to distant places by wind.

When rain drops, the radioactive particles fall on the ground, it is called fall out.

Strontium-90 accumulates in the bones, replaces calcium and may cause bone cancer and tissue degeneration in most animals and man.

The operation of a nuclear power plant releases large amounts of energy.

This energy is used in large turbines, which produce electricity.

Wastes from atomic reactors also contain radioactive materials.

The biggest problem is the disposal of these radioactive wastes.

If these wastes are not properly disposed off, can harm the living organisms wherever they may be dumped.

NOISE POLLUTION

The quality of our environment is judged, apart from other factors, by the amount of noise present.

Noise has been defined as "unwanted sounds" which is being "dumped" into the atmosphere to disturb the unwilling ears.

It adversely affects our physiological and mental health.

Noise is measured by a sound meter and is expressed in a unit called decibel (dB).

Any value more than 80 dB causes noise pollution.

Noise becomes unbearable at 140 dB.

The quietest sound that man's ear can detect is known as threshold of hearing.

A noise that hurts one's ears and gives headache is called threshold of pain.

The role of sound vibrations is measured in cycles per second (cps) or hertz (Hz).

The ear is potentially liable to damage, if it receives high intensity noise.

Noise in general is a physical form of pollution.

It has no persistent adverse effects on the life supporting systems but, has direct effects on the recipients.

Moderate conversation = 60 dB

Loud conversation = 70 dB

Scooter = 80 dB

Truck / Bus = 90 dB

Jet aeroplane = 150 dB

Rocket = 180 dB

Zone-wise permissible ambient noise levels (acoustic zoning) are given below. (According to central pollution control board)

I. Sources of Noise Pollution

Noise can either be natural like thundering sound or man made. The main sources of man made noise pollution are:

(i) Annoying and damaging sounds of various industries.

(ii) Defence material like rockets, tanks etc.

(iii) Entertainment sources like record players, radios, cassette players, loud speakers etc.

(iv) Transport automobiles and other vehicles such as trucks, buses etc.

II. Effects of Noise Pollution

Noise causes some serious damaging effects which are briefed as follows :

(i) Diminish hearing. Noise damages the ears, causes temporary or permanent noise induced hearing loss, depending upon the intensity and duration of the noise level. It leads to auditory fatigue and may finally lead to deafness. A sudden loud noise of any explosion may damage the tympanic membrane permanently. Sudden noise is more harmful than the continuous one. Factory workers suffer chronic hearing loss after many years of occupational noise exposure.

(ii) It has adverse effects on thinking and coordination of limbs.

(iii) Noise affects verbal communication on which we depend in all kinds of environment.

(iv) Noise increases blood cholesterol level, causes high B.P., digestive spasm, decreased heart output, defective night and colour vision. It impairs the development of nervous system of unborn babies which leads to abnormal behaviour in later life.

Control of Noise Pollution

Noise pollution can be controlled by following measures :

(i) Green muflur scheme. Trees such as Neem and Ashoka absorb sound vibrations to a great extent. Plantation of these trees on both sides of the roads, around silent zones reduces the menace of noise pollution.

(ii) Sound absorbing material should be used for reducing industrial noise.

(iii) Noise producing agencies should be located far away from residential areas. Vehicular traffic should be directed away from the human dwellings, educational institutions and hospitals etc.

(iv) General awareness should be developed among the people to minimize noise pollution in the environment.

Greenhouse effects and global warming

Effects of Green House Gases

(a) CO2 fertilization effect: Increase in atmospheric concentration of CO2 increases productivity of C3 plants and decreases rate of transpiration due to partial stomatal closure.

(b) Possible Effects of Global Warming

(i) Increasing of global temperature (increased 0.6°C, most of it during last 3 decades) and more extreme climatic conditions [EI Nino effect].

(ii) Warming of troposphere and cooling of stratosphere and thermosphere.

(iii) Global warming will push tropics into temperate areas and temperate areas towards pole (shifting of climatic zones) and higher altitudes in mountains resulting into changed species distribution.

(iv) Melting of ice caps.

(v) Rising of sea level, changes in rainfall pattern.

Control measures -Reduced deforestation, cutting down use of fossil fuel, planting trees, slowing down population growth.

GLOBAL ENVIRONMENT CHANGE

CO2, CH4, N2O and CFCs are radiatively active gases and also called green house gases.

The increased amounts of these gases in atmosphere is affecting the global climate and this phenomenon is known as global climatic change.

I. Green House Gases and Global Warming

(i) Term green house effect was coined by Arrhenius.

(ii) Green house gases trap the long wave radiations. A part of this energy is re-radiated back to the surface of earth. The downward flux of long wave radiation by green house gases is called green house flux.

(iii) The phenomenon of keeping the earth warm due to presence of certain radiatively active gases in the atmosphere is called green house effect, without which the average temperature of earth would have been between -18°C to -20°C rather than present average of 15°C.

Relative contribution of different green house gases to global warming

(iv) The excessive increase in concentrations of these gases in the atmosphere would retain more and more of the IR -radiation (long wave radiations), resulting in enhanced green house effect.

(v) CFC is most effective green house gas (effectiveness is 14,000 times more than CO2),

Ozone depletion in the stratosphere

Ozone Depletion

(i) Ozone layer is present in stratosphere at altitude of 23-25 km (conc. 0.3 ppm) and act as shield against UV radiation.

(ii) Large hole has appeared in ozone shield over Antarctica and smaller one over North pole. (Discovered by Farman 1985).

(iii) Ozone is commonly called as chemical weed, 'Bad' ozone is formed in troposphere that harms plants and animals. Good ozone is found in stratosphere as shield.

(iv) ODS: ozone depleting substances -CFC, CH4, CCl4, halons and N2O causes destruction of O3.

(v) CFC's are most damaging. They release Cl free radicals in stratosphere which destroy O3.

(vi) Thinning of the ozone-layer results in an increase in the UV-B radiation.

(vii) UV -B damages DNA and mutation may occur. It causes aging of skin, damage to skin cells and various types of skin cancers. A high dose of UV-B causes inflammation of cornea called snow blindness.

(viii) Nowadays CFC's are being replaced by Hydro Fluoro Carbons (HFCs).

Degradation by improper resource utilisation

DEGRADATION BY IMPROPER RESOURCE UTILISATION AND MAINTENANCE

The lowering of quality, fertility and productivity of land by various factors such as salination of soil, soil erosion, desertification, shifting cultivation and developmental activities etc. is called land degradation. It is caused by five main factors :

(i) Developmental activities:

Many developmental activities such as rapid urbanisation, human settlement, mining, construction of roads, dams, canals, railways, airports, playgrounds, industries cause loss of large areas of fertile and productive land.

(ii) Soil erosion:

It is the removal of top, fertile, mineral rich soil layer by water, floods, wind, ocean waves, glaciers, felling of trees, overgrazing on slopes or some arid soils, over cropping and improper farming techniques etc. It occurs in both wet and arid regions. Roots of grasses are excellent binding material and keep the soil intact and free from soil erosion.

(iii) Desertification:

It is the change of fertile soil into a non productive desert soil. It is due to the shifting of sand dunes by strong winds, or by deforestation, soil erosion or overgrazing in lands sparsely covered by grasses. Many deserts in the world are man-made. Afforestation is the only solution to prevent desertification.

(iv) Shifting cultivation:

In many tribal communities of tropical and subtropical regions of Africa and Asia, it is a practice of slashing, cutting down trees, burning the felled trees and raising crops on the ash formed. This practice is called 'Jhum Cultivation' in north east India. This destroys forests and causes soil erosion.

(v) Salination of Soil:

Increase in the concentration of soluble salts in the soil is called salination. Origin or development of saline soil depends upon following factors:

(a) Poor Drainage of Soil: Salts dissolved in irrigation water accumulate on the soil surface due to inadequate drainage especially during flood.

(b) Quality of Irrigation Water: The ground water of arid (dry, barren having not enough rainfall to support vegetation) regions are generally saline in nature. The irrigation water may be itself rich in soluble salts and add to salinity of soils.

(c) Excessive use of basic fertilizers: Excessive use of alkaline fertilizers like sodium nitrate, basic slag, etc may develop alkalinity in soil.

(d) Saline nature of parent rock materials: If soil develops from saline nature of parent rock materials, soil would be saline.

Control of degradation : Degradation can be checked by the following measures :

(i) Reforestation and plantation of grassess can check soil erosion, floods and water logging.

(ii) Crop rotation and mixed cropping improve fertility. It would increase production, which would support large population.

(iii) Salinity of the soil can be checked by providing adequate drainage.

(iv) Desertification can be checked by artificial bunds or covering the area with suitable soil binding vegetation.

Deforestation

DEFORESTATION

It is the conversion of forested areas to non-forested ones. It is estimated that almost 40 per cent forests have been lost in the tropics, compared to only 1 per cent in the temperate region.

At the beginning of the twentieth century, forests covered about 30 per cent of the land of India. By the end of the century, it shrunk to 19.4 per cent, whereas the National Forest Policy (1988) of India has recommended 33 per cent forest cover for the plains and 67 per cent for the hills.

Trees are axed for timber, firewood, cattle ranching and for several other purposes. Slash and burn agriculture, has also contributed to deforestation.

One of the major effects of deforestation is increased carbon dioxide concentration in the atmosphere. It also causes loss of biodiversity due to habitat destruction, disturbs hydrologic cycle, causes soil erosion, and may lead to desertification in extreme cases.

Reforestation is the process of restoring a forest it may also occur naturally in a deforested area.

Case Study of People's Participation in Conservation of Forests

A Bishnoi woman of Khejarli village, Jodhpur, Rajasthan named Amrita Devi showed exemplary courage by hugging a tree.

Amrita Devi Bishnoi Wildlife Protection Award - for individuals or communities from rural areas that have shown extraordinary courage and dedication in protecting wildlife.

Chipko Movement. It is movement which was initially meant for protecting trees but not meant for preservation of environment including habitat and wildlife. Chipko movement was born in March 1974 in Gopeshwar in Chamoli district. The movement has two leaders, Chandi Prasad Bhatt of Gopeshwar and Sunder Lal Bahugana of Silyara in Tehri region. A similar movement was undertaken by Paudurang Hedge in the South. It is known as appiko movement.

Government of India in 1980s has introduced the concept of Joint Forest Management (JFM) so as to work closely with the local communities for protecting and managing forests.

ENVIRONMENTAL LAWS FOR CONTROLLING POLLUTION

Important legislations directed at the protection of environment in India are listed below:

(i) The Environment (Protection) Act, 1986

(ii) The Insecticide Act, 1968

(iii) The Water (Prevention and Control of Pollution) Act, 1974

(iv) The Air (Prevention and Control of Pollution) Act, 1981 (Amended in 1987 to include noise as an air pollutant.)

International Initiatives for Mitigating Global Change

The long-term challenge of stabilising the atmospheric concentrations of greenhouse gases requires that global emissions be significantly lowered than what they are today.

In 1987, many countries signed the Montreal Protocol (effective in 1989) at Montreal (Canada), a landmark international agreement to protect the stratospheric ozone by agreeing to limit the production and use of ozone-depleting substances, phasing out of ozone-depleting substances and helping the developing countries to implement use of alternatives to CFCs.

The United Nations Conference on Environment and Development (UNCED, Earth Summit), held at Rio de Janeiro, Brazil in 1992, established the principles for reducing greenhouse gas emission.

The Kyoto Protocol, approved by a follow-up conference held in Kyoto, Japan, during December 1997, has specified the commitments of different countries to mitigate climate change.

This protocol requires countries to take appropriate measures to reduce their overall greenhouse gas emissions to a level at least 5% below the 1990 level by the commitment period 2008-2012.