Here is a compilation of essays on ‘Air Pollution’ for class 8, 9, 10, 11 and 12. Find paragraphs, long and short essays on ‘Air Pollution’ especially written for school and college students.
Essay on Air Pollution in India
- Essay on the Introduction to Air Pollution
- Essay on the Causes of Air Pollution
- Essay on the Sources of Air Pollution
- Essay on the Types of Sources of Air Pollution
- Essay on the Major Air Pollutants
- Essay on the Effects of Air Pollution on Animals and Human Beings
- Essay on the Ill-Effects of Acid Rain
- Essay on the Effects of Air Pollution on Plants
- Essay on the Aesthetic Aspect of Air Pollution
- Essay on the Effect of Air Pollution on Climate
- Essay on the Control of Air Pollution
- Essay on the Use of CNG: A Case Study of Delhi
Essay # 1. Introduction to Air Pollution:
Generally in non-industrial and rural areas at normal temperature and pressure the air present in the atmosphere may be called as pure air. But, in industrial and urban areas the air present in atmosphere is called as impure air or polluted air due to the presence of chemical gases (carbon monoxide, carbon dioxide, sulphur dioxide, nitrogen oxide, hydrogen sulphide etc.), dust particles, smokes and the liquid droplets which are known as pollutants.
The air pollutant is a substance when added to air causes adverse effects on the health of human beings, animals, birds, insects, aquatic animals and eco-systems. Pollutants may be poisonous solid particles, liquid droplets or gases. A pollutant may have a natural origin or manmade. Therefore pollutants as classified as primary and secondary.
Primary pollutants are generally produced by the natural processes such as volcanic eruptions and burning of organic fuels like coals, wood, dried crop wastes and cow dungs. Other examples of primary air pollutants are carbon monoxide, carbon dioxide gases produced from the motor vehicle exhausts or sulphur dioxide gas released from factory chimneys.
The secondary pollutants are not emitted directly but are formed in the atmospheric air by the chemical interactions of primary pollutants with the chemical gases already present in the atmospheric air. Any type of pollutant present in pure air causes pollution and becomes a threat to human health, animal health, aquatic animal health and earth’s eco-system.
As “the prevention is better than cure”, men and government authorities must be careful now onwards to prevent the air pollution, otherwise the survival of the living beings will be impossible on this earth.
Air pollution is defined as the occurrence of foreign particles or gases in the atmosphere which are harmful to man, vegetation, animals and buildings. Air is one of the most important constituents of man’s environment. Clean and pure air is very essential for health and survival of man. Air pollutants can be gases or particulate matter (e.g. suspended aerosols and SPM).
Essay # 2. Causes of Air Pollution:
Development economists, in recent times have emphasized on acceleration of economic growth for raising per capita incomes of people and industrialization holds the key for rapid growth of the economy. Air pollution is abundant in areas where industries, like petroleum refineries, textiles and pulp and paper are located.
Ecological degradation in form of air pollution is the upshot of increasing traffic use, the presence of bad roads, traffic congestion and use of old vehicles and absolute technologies. The existence of slums, badly ventilated houses, smoking cigarette, use of old methods of cooking like wood and coal precipitate air pollution. The use of pesticides by spraying in fields increases the quantity of chemicals used in surrounding atmosphere.
Mining activities involving blasting excavations, crushing and transportation of ore are common these days. Huge quantities of dust become windborne. Thermal power stations use the combustion of coal or petroleum for generation of heat and power, and produce smoke and SO2 (Sulphur dioxide).
Burning of heaps of solid wastes, diesel generation sets, population growth, air conditioning appliances and construction activities are some of the constellation of factors accounting for air pollution. Reference may be made of Greenhouse effect, which denotes the phenomenon by which the earth’s atmosphere traps infrared radiation or heat.
Water vapour, CO2, Methane and Nitrous oxide, no doubt keeps the earth habitable. But, human activities cause mounting concentration of these gases known as chlorofluro carbons (CFCS). Piles of evidence have accumulated in recent years to suggest that global warming has accelerated in the recent past.
World glaciers inventory spot lights that, most glaciers around the world have retreated since the turn of the century. It is logical to state that, tropical glaciers and icecaps are sensitive to climate change and may serve as an index to global warming.
It is plausible to believe that atmospheric particulate due to fuel consumption for industrial and heating purposes can scatter and absorb sunlight and may reduce visibility. Among the adverse effects of particulate matter we include corrosion of metals, erosion and soiling of sculptures and buildings.
It follows that agricultural and industrial development sets in motion the tragic drama of ecological degradation. Possible fuel energy policy pursued by several global economies is not environmentally sustainable. It is alarming to note that more than half of words twenty major cities are confronted with air pollution that sets in motion premature deaths and economic losses, There is particulate matter inform of dirt, dust and solid waste that is thrown into the air that is baneful for humans, animals and plants.
Essay # 3. Sources of Air Pollution:
The sources of air pollution are very large and varied.
Few of them are:
1. Industrial Pollutants:
Common air pollutants which are discharged into air from industrial chimneys and power houses are CO2, CO2, SO2, H2S and hydrocarbons. These gases are produced due to burning of coal and petroleum and by combustion of lignite at thermal power stations. Many metallurgical processes release dust and fumes which are loaded with lead, chromium, nickel etc.
Many chemical industries release hydrochloric acid, chlorine, nitrogen oxide, zinc, lead, arsenic, oxides of copper in addition to SO2, CO and H2S. The industries constitute second major contributor to Delhi’s atmospheric pollution, but in Mumbai, main source of pollution are industries.
2. Mobile Combustion Sources:
These sources include locomotives, aircrafts, automobiles etc. Automobiles are the largest source of air pollution in big cities. In Delhi alone, about 1,000 new cars hit the roads every day. In Delhi, about 2000 million tons of pollutants are pumped into the environment every day out of which about 1300 million tonnes (about 70%) are added by 3 million vehicles, two- thirds of which have two-stroke engines.
The combustion of petroleum emits various particulate lead compounds. Automobiles release CO (77.2%), nitrogen oxide (7.7%) and hydrocarbons (13.7%). Every gallon of petrol consumed by automobiles produces 3 lbs of CO and 15 lbs of nitrogen oxide which is sufficient to pollute 800,000 to 2,000,000 c.c. of air. Approximately 312 tonnes of lead is let out into Delhi’s atmosphere every year. The main culprits being goods transporting vehicles.
The fact that petrol-run two and four wheelers collectively add about half a million tonnes of lead in the Indian environment every year. This can endanger the people to dead lead poisoning. In Delhi, lead emission has increased by 100 times in 1987 than in 1977.
In 1997, about 1.68 lakh meric tonnes of pollutants were added in Delhi’s atmosphere which is about 50% more than those emitted in 1987 (87,000 metric tonnes).
3. Burning of Fuels:
Fossil fuels provide us energy for cooking, heating and lightening of our houses. Among fossil fuels coal and oil are the major sources of energy. Coal on combustion produces CO2. Incomplete combustion yields CO and a variety of hydrocarbons including methane and soot. Burning of coal produces SO2 and ash also.
4. Agricultural Activities:
About 60 to 65% of carbon dioxide is produced from burning of forests and savannah grassland to clear areas for pastures and cropland. About 40% of methane is produced from paddy fields, guts of livestocks and also from burning of biomass. Crop spraying and dusting for pest and weed control are responsible for emitting organic phosphates, chlorinated hydrocarbons, arsenic and lead into the air.
5. Ionizing Radiations:
Ionizing radiations like α-, β-particles and gamma rays are produced in atomic piles of nuclear power during nuclear explosions, during scientific experiments and testing of atomic weapons.
6. Suspended Particulate Matter (SPM):
SPM is a major air pollutant. Dust is generated from sources such as coal dust (from oil refineries, power plants), cement dust, silica dust (from stone crushing). A huge amount of dust is also blown by transport vehicles.
Essay # 4. Types of Sources of Air Pollution:
Sources of air pollution are divided into 3 categories:
1. Point or Fixed or Stationary Sources:
These add the pollutants to certain restricted and specific area through their tall chimneys e.g., industries, electrical power plants, mineral smelters, etc.
2. Line or Mobile Sources:
These add the pollutants along narrow belts over long distance e.g., automobiles, aircrafts, jet planes, etc.
3. Area Sources:
These add smoke and gases over wide areas e.g., cities and towns.
Essay # 5. Major Air Pollutants:
1. Carbon Monoxide:
This is produced due to incomplete combustion of fuels (especially petroleum). Other sources of CO are metallurgical operations, cigarette smoke, etc. It accounts for about 50% of total air pollution. It is formed by incomplete combustion of carbon fuels in industries, vehicles, kitchens etc. About 50% of CO emission originates from the automobiles. Carbon monoxide is the largest pollutant in Delhi’s air. In 1997, CO emission was about 132 times more than that in 1987. Over 15 million tonnes of CO are added to the environment every year.
2. Carbon Dioxide:
It is released due to combustion of fuels in homes, factories etc. It is also produced during the process of respiration and volcanic eruptions. CO2 content of air has increased by about 15% in the last 100 years mainly due to deforestation, burning of fuels and release of CO2 from the sea.
3. Sulphur Dioxide:
The gaseous SO2 oxidises to SO3, which on combination with water forms sulphuric acid. Lichens are very sensitive to SO2. It is mainly produced due to coal burning (maximum SO2 addition and accounts for 6% of pollution); ore-smelters and oil refineries. The presence of increasing concentration of H2SO4 vapours leads to occurrence of acid rain (Fig. 16.1).
Acid rain is 60-70% due to SO2 and SO3; and 30-40% due to NO2 and NO3. Rainfall pH value has been estimated to be in between 5.6 to 6.5 (due to formation of weak carbonic acid formed by reaction between CO2 and water) in Bangalore, Delhi, Nagpur and Pune but may be as low as 4.0 pH. A study has shown that main sources of oxides of sulphur are volcanoes (67%), industries (22%) vehicles and forest fires.
These are the chemicals which are present in air in the form of vapours or fine mist. Aerosols are used as disinfectants. They are also emitted from jet planes and contain chlorofluorocarbons (CFCs). Chlorofluorocarbons (e.g. Freon gas) are also used in air conditioners and industrial refrigerators as the coolants.
These were used in aerosols as the gas and also as cleaning agents in electronic industry. Burning of plastics releases polychlorinated biphenyls (PCB).
Fluorides are released during refinement of aluminium, rock phosphates etc.
This is a type of carcinogen produced in tobacco smoke, industrial effluences and automobile exhausts.
7. Nitrogen Oxides:
They are produced from nitrates, nitrites, electric storms by biological and non-biological activities. These are produced due to combustion process of fossil fuels at high temperatures in industries, automobiles, nitrogen fertilizer plants, etc. These include NO, N2O, NO2 N2, O4, N2O5, etc. About 33,000 tonnes of nitrogen oxides are added in Delhi’s air annually. They act on unsaturated hydrocarbons to form peroxyacyl nitrates or PAN. Nitrogen oxide is responsible for forming photochemical smog. It also forms a part of acid rain.
8. Photochemical Oxidants (Fig. 16.3):
Many unburnt hydrocarbons react with oxides of nitrogen to form ozone, peroxyacyl nitrates (PAN), aldehydes etc.
Some photochemical oxidants are given below:
Ozone is stratosphere is responsible for protecting the earth from high energy ultra-violet radiations. It forms a life-saving screen as it checks the entry of lethal UV-rays. Ozone found in troposphere has warming effect. Ozone is one gas which is harmful as well as useful for human beings.
(b) Peroxy-Acyl Nitrates:
Some of the peroxy-acyl rutrates are peroxy-acyl nitrate (PAN), peroxy-propionyl nitrate (PEN) and peroxy-buteryl nitrate (PBN). They cause eye irritation, respiratory distress. They affect foliage by glazing, necrosis and silvering etc.
Aldehydes produce irritation in gastrointestinal and respiratory tracts.
They cause damage to liver, lungs etc.
It is produced by the combination of smoke and fog.
It is an unsaturated hydrocarbon produced from incomplete combustion of coal, wood, petrol, cigars etc.
11. Indoor Pollution:
These include combustion of fuels and tobacco smoking, air conditioning and near- zero ventilation in the congested buildings. Formaldehyde emitted from newly-manufactured carpets also causes indoor pollution.
These not only produce obnoxious fumes which pollute the immediate environment, but also cause noise pollution. The fumes contain CO, carbon particles and polyaromatic hydrocarbons. So investors are better because these are noise-free and do not produce obnoxious fumes. But now zero-polluting and soundless generators are also available.
These are volatile organic carbons (VOCs) compounds. Several aliphatic and aromatic gaseous hydrocarbons are known as pollutants. These may be saturated (CH4) or unsaturated (ethylene). Most of the hydrocarbons are added by burning of petroleum. Methane is added by anaerobic decay of organic matter.
The plants like pine trees also produce some hydrocarbons like terpenes, isoprene, etc. Methane is most abundant hydrocarbon in the atmosphere. It is mainly produced by rice fields (about 40%) and swamps. Benzene is a major constituent of petrol and automobile exhaust. In 1997, hydrocarbons emission was about 224 times than that in 1987.
14. Particulate Matter:
It is the non-gaseous matter in the atmosphere. Main sources of particulate matter are industries which include cotton dust, iron mill dust, mine dust, flour mill dust, germ grinding, cement factories, etc. It occurs either as liquid (e.g. aerosols) or solid state suspended in the air. It is of 2 types: settable (longer than 10 (xm) and suspended.
The later is again classified into 3 categories:
Less than 1 µ.m.
Solid (e.g. of coal, wool, pesticides, metals like Hg, Pb, Cu and Fe, biological agents like pollens and dust mites) and more than 1 µ,m.
Liquid and more than 1 µ.m.
It is added in the atmosphere by burning of fuels in houses and industries. It causes about 10-15% of air pollution.
Essay # 6. Effects of Air Pollution on Animals and Human Beings:
1. Lead is known to damage kidney, liver, reproductive system, blood formation, basic cellular processes and brain functioning so causing anaemia, neurological disorders, behavioural disturbances, muscle paralysis, hypertension, etc.
2. Hydrocarbons are known to cause eye-irritation, coughing, sneezing, drowsiness, etc. Benzene and its derivative formaldehyde are well known carcinogen causing leukemia.
3. Carbon monoxide. It readily binds (about 200 times faster) the haemoglobin so decreasing its oxygen carrying capacity leading to hypoxia in body tissues. It causes headache, muscular weakness, nausea, exhaustion, psychomotor disturbances, etc. When 50 per cent of haemoglobin has been transformed into carboxy haemoglobin (HbO2 + CO ↔ HbCO + O2), then death occurs due to CO-poisoning leading to anoxia.
4. Nitrous oxides decrease gaseous exchange in blood and hinder the functioning of lung NO2 inhalation causes eye irritation, lung oedema, blood congestion. It is also a mutagen.
5. SPM of troposphere penetrates deep into respiration system and causes ailments like bronchitis, asthma, cardiovascular problems, etc. SPM is the most serious air pollutant which is resulting in about 460,000 additional deaths every year, out of which 135,000 are lung-related and about 90,000 are due to heart-related diseases.
6. Two-wheeler riders, traffic policemen and roadside stall owners in areas with dense traffic have been found to suffer from a new ailment called dry eyes. It is characterized by irritation of eyes, redness in cornea and corneal damage, if left untreated.
7. Ill effects of thinning of ozone layer have been discussed in Air pollutants and Radioactive pollution.
8. Sulphur dioxide increases the chances of occurrence of asthma, bronchitis, emphysema etc. when above 1 ppm. It also has mutagenic properties.
9. Benzpyrene of tobacco smoke N-Nitrosomethylene of soot are carcinogenic.
10. Chlorofluorocarbons (CFCs) undergo biomagnification and may reach upto a level of 1400 mg/kg of pectoral muscles in sea eagle and 3.5 mg/ kg of fat in mother’s milk. These impair reproductive activities of animals and damage the liver, CNS, vision, etc. in human beings.
11. Ozone damages the mucous membrane at a concentration of even less than 1 ppm.
12. Peroxy acyl nitrates cause eye irritation and respiratory problems.
13. Phenols damage spleen, kidneys, liver and lungs.
14. Aldehydes cause irritation in gastro-intestinal and respiratory tracts.
15. Smog causes respiratory disorders like asthma, allergies, etc.
16. At a concentration above 150 mg/100 m3 cotton dust causes pneumoconiosis or lung fibrosis called byssinosis. Other respiratory disorders due to particulate matter are emphysema, siderosis, etc.
17. Indoor pollution stimulates the production of mucus and sputum. A recent study has reported that over five lakh Indians die every year due to indoor pollution.
Essay # 7. Ill-Effects of Acid Rain:
1. Acid rain damages a number of heritage monuments due to deposition of acids e.g. statue of liberty and Taj Mahal of Agra.
2. Acid rain below 5 pH causes death of planktons, molluscs and fish in the aquatic systems so disturbs the food chains.
3. Acid rain also kills the useful soil microbial community so disturbing the terrestrial ecosystems.
Essay # 8. Effects of Air Pollution on Plants:
1. The soot and smoke particulate material settles on leaves and reduces the rate of photosynthesis.
2. Fluorides in air cause chlorosis, necrosis of margin and tip, and abscission of leaves.
3. The photochemical smog is responsible for bleaching of the foliage of certain plants. It also causes silvering, glazing and necrosis of the leaves.
4. The hydrocarbons lead to premature leaf fall and fruit drop (abscission).
5. Lichens are sensitive to air pollution. They are grown as pollution indicators. Garden pea is another SO2 pollution indicator.
6. Pollutants can also breakdown the waxy coating on the leaves that helps to prevent excessive water loss and damage from pests, diseases, drought etc.
7. SO2. It causes chlorosis and necrosis of vegetation in as low concentration as 0.032 ppm. Lichens like Parmelia, Usnea, Cladonia and mosses are completely destroyed. SO2 also causes membrane damage, metabolic inhibition, yield reduction, etc. High concentration of SO2 causes chlorosis. Most affected component of living cells is cell-membrane system.
8. Oxides of nitrogen cause lesion, necrosis, defoliation, die back and death of many plants.
9. Ozone destroys chlorenchyma and produces necrotic areas at concentration of only 0.02 ppm. It destroys the crops of potato, alfalfa and spinach upto the extent of 50%. It also damages the leaves of tobacco, tomato and pines.
10. Peroxy-acyl nitrates damage the chloroplasts (Fig. 16.7) so impair photosynthesis, ETS of respiration.
11. Ethylene. It causes premature senescence and abscission in many plants especially in orchids and cotton.
Essay # 9. Aesthetic Aspect of Air Pollution:
1. Coal, dust etc. are a source of nuisance for households and impart a dirty look.
2. Gases like oxides of sulphur and nitrogen along with smoke make breathing difficult.
3. A clear and transparent atmosphere is aesthetically pleasant to human beings. Presence of smoke and dust in air irritates the human mind.
4. The stone of Parthenon in Althens has deteriorated in the past 50 years from air pollution.
5. Similarly, Statue of Liberty is corroded from SO2 and NO2, and Taj Mahal from SO2 emitted by Mathura refineries. The pollutant gases may transform marble (CaCO3) of Taj into calcium sulphate and calcium nitrate.
Essay # 10. Effect of Air Pollution on Climate:
Dust, smoke and other suspended particulate matter reduce the visibility. Particulate matter of stratosphere changes the thermal budgets of the atmosphere and decreases the atmospheric temperature. Flyash also affects visibility. Some of the aerosols as sulphuric acid mist, ammonium sulphate mist and water vapours influence the vertical temperature profile in the atmosphere.
It affects thermal mixing. It also leads to greenhouse effect and depletion of ozone layer. Ozone acts as an oxidant and damages the marble statues and surfaces of heritage buildings. Due to CFCs, there is a hole in the ozone shield over Antarctica. Thinning of ozone shield will allow shorter and high energetic UV- radiations in earth’s atmosphere and cause extensive damage to plants as well as animals.
Essay # 11. Control of Air Pollution:
Three methods can be undertaken for control of air pollution.
Separation of Pollutants:
This can be achieved by the following methods:
(a) Sulphur free and lead free fuel should be used for motor vehicles. Use of sulphur-free diesel can reduce the air pollution by 50%.
(b) Automobiles should be made more fuel efficient and less taxing on environment. Multipoint fuel injection engines should be used to reduce the unburnt hydrocarbons from the emission of automobiles. It has been established that installation of catalytic converters can slash carbon monoxide emission from 90 grams to 3.4 grams per mile run.
So if half the vehicles on Delhi and Mumbai roads are made to install such catalytic convertors, then total CO emissions in India can be reduced by 70 per cent. These catalytic converters have metals like platinum-palladivim and rhodivim which act as catalysts. These convert the unburnt hydrocarbons to CO2 and water. Carbon monoxide to CO2 and nitric oxide to nitrogen gas. So the catalytic converters reduce the emission of pollutant gases.
(c) Fuel refining policy must be changed so that the emission levels could be drastically reduced.
(d) Reformulate gasoline to save ozone in the atmosphere.
(e) An urgent need of effective traffic management as a standing vehicle with its engine switched on could emit seven times higher smoke than when running on a road.
(f) Non-combustible sources of energy should be developed.
(g) Use of generators in the residential areas should be avoided.
(h) In factories, chimneys should be tall to reduce the rate of pollution at ground level.
(i) To remove the particulate matter in the smoke, it should be filtered before releasing it into the air.
(j) Plantation (Afforestation) should be done on a large scale. Plants like Ficus variegata, Daucus carrota, Phaseolus vulgaris, Coleus bulmei can fix carbon monoxide easily. Some other plants like Pinus, funiperus, Quercus, Vitis, Ribes, Rhamnus, Craetagus etc. can use nitrogen oxides. Trees use carbon dioxide and release oxygen and depollute the air.
(k) Devices to control particulate matter. Particulate matter of the polluted air can be separated by two types of devices called arresters and scrubbers.
Arresters are again of several types like electrostatic precipitators (ESPs), Cyclone separators. Trajectory separators. Gravity settling chamber and filters.
i. ESPs (Fig. 16.13):
These are electrical devices which separate the particulate matter on the basis of their charges. In them, the electrically-charged particulate wastes are attracted on oppositely charged electrode wires of collecting surfaces. These are employed in thermal power plants, and industries involved in power generation, petroleum and oil refineries, cement plants, paper mills, metallurgical plants, sludge incineration, etc.
These can remove the particles even in the size range of 5-20 mm and can remove them to the extent of 99 per cent but the velocity of air must be low to provide enough period to allow the dust to fall. It is the most effective device to remove particulate pollutants.
ii. Cyclone Separator (Fig. 16.14):
In this, an incoming dust-laden gas stream is transformed into a combined vortex from which centrifugal forces tend to drive the suspended particles to the wall of the body of the separator.
iii. Bag House Filters (Fig. 16.15):
In these, dust-laden fumes are passed through the filtering devices formed of porous mats of polyster, teflon, polyamide, wool, cloth fabric, cellulose, etc. The particles are held by the filters while the clean gases pass through them.
Scrubbers (Fig. 16.16):
These are formed of dry or wet packing material and are used to separate dust particles and toxic gases (especially SO2) from air. In this, the polluted air is forced into scrubbers while a counter current of water is passed through a spray tower at the top. Spray tower releases drops of water or lime from a number of spray nozzles. Water drops remove the particulates as well as toxic gases, while lime removes SO2 as calcium sulphate or sulphite. Wet scrubbers are used in chemical mining and metallurgical industries to trap SO2, ammonia, metal fumes, etc.
Essay # 12. Use of CNG: A Case Study of Delhi:
Though industries, thermal power plants and domestic activities also contribute to air pollution in cities, but the automobile sector is the largest polluting source of air pollution. Delhi has more cars than the states of West Bengal and Gujarat put together. Vehicular pollution is responsible for about 64 per cent of total air pollution in Delhi, 32 per cent in Mumbai and 30 per cent in Kolkata.
In Delhi alone, about 2000 million tonnes of pollutants are pumped into the environment every day. Out of which about 65% (i.e. 1300 million tormes) are added by about 3 million vehicles, two- thirds of which have two-stroke engines. Automobiles release CO (77.2%), nitrogen oxide (7.7%) and hydrocarbons (13.7%).
The main culprits being goods transporting vehicles. It was calculated that in 1997, about 1.68 lakh metric tonnes of pollutants were added in Delhi’s atmosphere which was about 50% more than those emitted in 1987. These air pollutants have many health hazards for human beings.
In 1998, Central Government constituted a multimember agency, called Environmental Protection Authority (EPA), to monitor and tackle all the aspects of pollution in the National Capital Region (NCR). With an aim to reduce air pollution in NCT (National Capital Territory i.e. Delhi) due to vehicular pollution. Supreme Court in July 1998 directed the Central Government to convert all the 10,000 diesel- run buses to operate on a cleaner fuel Compressed Natural Gas (CNG) latest by 2002.
Now Delhi is the only city in the world having its whole public transport system using only CNG. CNG is called cleaner fuel because its combustion releases less pollutants. Presently, all the buses of DTC and private agencies and auto-rickshaws in Delhi are being run on CNG. This has greatly reduced the pollution level of CO2 and SO2 in Delhi’s air. Other benefits of CNG over diesel are it is cheaper, cannot be siphoned off by the thieves and cannot be adulterated.