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Text Book Question and Answers
I. Choose the correct answer from those given, for the following questions.
1. Identify from the following a biodegradable pollutant
(a) Oxides of sulphur (b) sewage water (c) lead compounds (d) pesticides
Answer: (b) sewage water

2. Which of the following is the most hazardous air pollutant?
(a) Oxides of nitrogen (b) Carbon di oxide (c) Carbon monoxide (d) Oxides of sulphur
Answer: (c) Carbon monoxide

3. Agricultural wastes are causing
(a) Water pollution (b) Both water and Land pollution (c) Air pollution
Answer: (b) Both water and Land pollution

4. Acid rain refers to precipitation with a pH of
(a) less than 5.6 (b) about 7.0 (c) above 6.0 (d) above 7.0
Answer: (a) less than 5.6

5. Which of the following chemical element is responsible for breaking down ozone in the atmosphere?
(a) Mercury (b) Carbon (c) Lead (d) Chlorine
Answer: (d) Chlorine

6. Global warming can be reduced by minimising the release of
(a) Chlorofluorocarbons (b) sewage water (c) greenhouse gases (d) agricultural wastes
Answer: (c) greenhouse gases
II. Fill in the blanks with suitable words
1. Waste incineration releases mainly Carbon monoxide
2. Detergents cause a decrease in the Oxygen content of water
3. Ozone in the atmosphere protects us from harmful ultra violet radiation
4. Oxides of nitrogen and sulphur are mainly responsible for causing Acid rain
5. Noise beyond is dangerous to human ear 100 decibel
III. Answer the following questions
1. Distinguish between biodegradable and non-biodegradable pollutants. Give examples
Biodegradable pollutants: Pollutants that can be degraded by biological activity are called biodegradable pollutants. Example: sewage, excreta of animals, plant residue, sulphur dioxide, animal dung, agricultural residue, forest residue, dead plant and animal.
Non-biodegradable pollutants: Pollutants which cannot be converted into harmless constituents non-biodegradable pollutants. Example: DDT (dichlorodiphenyltrichloroethane), lead, plastic,
2. Make a list of the main sources of air pollution.
The main sources of air pollution are
a) Coal combustion
b) Diesel combustion
c) Petrol combustion
d) Smoking of tobacco
e) Waste incineration
3. Define marine pollution. List two main causes.
Most of the pollutants reaching the atmosphere condense and fall into the oceans or sea, causing marine pollution.
Two causes are: (1) agricultural runoff (2) oil seepage (3) industrial effluents
4. Explain the need for treating sewage water.
Sewage is waste water from domestic activities such as cooking, cleaning, laundry or bathing. Exposure to sewage through ingestion or bodily contact can result in disease, severe illness, and in some instances death. Sewage water may contain many toxic chemicals, detergents, excreta of animals and humans. They may also house many bacteria, viruses and parasites which may cause deadly diseases. Therefore, it is important to treat sewage water and make it safe before letting it out to nature
5. Make a list of the effects of noise pollution.
Effects of noise pollution
§ Noise pollution directly affects the human nervous system, causing deafness, headache, high blood pressure and heart disorders.
§ Noise causes behavioural discomforts.
§ Noise pollution seriously affects animals.
6. Write a brief note on radio active pollution.
Radio activity is a phenomenon of emission of Protons (alpha particles), Electrons (beta particles) and Gama rays due to disassociation of atomic nuclei of some elements. Such emission also can cause pollution. This is called radioactive pollution.
Radiation is of two types
1. Ionising radiations have high penetration power and cause breakage of macro molecules.
2. Non ionising radiations affect only those compounds which absorb them.
Sources of radioactive pollution
· Nuclear power plants
· Nuclear weapons
· Disposal of nuclear wastes
· Use of radioactive Isotopes
· Uranium mining
Radioactive materials react with biological molecules. It can damage DNA. Leading to cancer and birth defects.
7. Suggest measures to control acid rain.
· Industries to be established away from towns and cities.
· Emissions from industries to be checked and controlled.
· Regulatory rules related to air pollution must be strictly enforced.
· Automobiles to be periodically checked to improve the efficiency of engines to minimise the emissions.
· Use of unleaded fuel and biofuels must be encouraged.
· Educating the public to use public transport.
· Measures of checking air pollution at sources are to be implemented.

Additional Question and Answers
1. What is pollution?
Any such undesirable change in the physical, chemical and biological characteristics of the environment is called Pollution.

2. What is pollutants?
Any substances which bring about undesirable changes are called pollutants.

3. Name the primary categories of pollutants with an example each
1. Biodegradable pollutants ex: plant waste.
2. Non-biodegradable pollutants ex: plastic, D.D.T.
4. What is meant by biomagnification?
Non-biodegradable pollutants can enter the food chain where at each tropic level. Their concentration keeps increasing. This phenomenon is called biomagnification.
5. Name the different types of environmental pollution.
Air pollution, water pollution, Land pollution, Noise pollution, radioactive pollution, Thermal pollution, marine pollution
6. What is air pollution?
Any human activity that brings about significant changes in the atmosphere is called air pollution.
7. Common air pollutants and their effects.
Sulphur oxides, particulatesCoal and oil power plants, Oil refineries, smelters, Kerosene stovesBronchial diseases
Carbon monoxideMotor vehicle emissions, Fossil fuel burningAsphyxia leadings to heart and nervous system damage, death
Oxides of NitrogenAutomobile emissions, Fossil fuel, power plants, Oil refineriesRespiratory disorders
Ozone(03)Ozone generators. Aircraft cabinsRespiratory disorders
Polycyclic aromatic hydrocarbonsDiesel exhaust, Cigarette smoke, Stove smokeLung cancer
AsbestosAsbestos mines and mills, Insulation, Building materialsLung cancer, Asbestosis
ArsenicCopper smelters, Cigarette smokeLung cancer
AllergensPollen, Animal dander, House dustAsthma, running nose
8. What are the consequences of inhaling air polluted with carbon monoxide on our health?
Carbon monoxide pollution impedes the transport of oxygen in our body. This causes asphyxia leading to the damage of the heart and nervous system. Continued inhaling of air polluted by carbon monoxide may also lead to death.
9. What are the health consequences of inhaling asbestos dust?
Inhaling asbestos dust leads to a type of cancer of the protective lining of the inner organs. Exposure to asbestos dust may also lead to lung cancer. Asbestos inhaling can also cause a disease that involves a scarring of lung tissue. This condition is called asbestosis.
10. Why is smoking of tobacco dangerous?
Smoking is injurious to health of not only the smoker but also of people around the person. Cigarette smoke has high content of carbon monoxide and arsenic which are highly poisonous. Carbon monoxide impedes the transport of oxygen in the body and causes harm to the lungs, blood vessels, heart and the nervous system. Smoking also contributes to air pollution. Hence, smoking tobacco is dangerous.
11. Mention some of the adverse effects of air pollution on human health.
The undesirable consequences of air pollution on our health include the following:
i) Polluted air causes respiratory disorders such as bronchial diseases, inflammation of the air passage and asthma.
ii) Air pollution by certain substances may cause several health problems including death.
iii) Excessive pollution by carbon monoxide impedes the transport of oxygen in the body which will in turn affect the health of the respiratory system, heart, blood vessels and nervous system.
iv) Pollution of the atmospheric air by certain chemicals will deplete the ozone layer which results in premature cataract and skin cancer.
12. Suggest some measures to control air pollution.
Some of the measures to control air pollution include the following:
i) Effective monitoring and strict enforcement of environmental laws.
ii) Treating industrial exhaust to remove toxic gases and particulate matter before they are let into the atmosphere.
iii) Keeping engines of automobiles in good condition and phasing out of old and inefficient Engines.
iv) Encouraging the use of unleaded petrol and bio fuels.
v) Encouraging the use of smokeless choolas.
vi) Establishing industrial units away from towns and cities.
vii) Providing incentives to use public transport instead of individual private transport.
viii) Building awareness among the public through education.
13. Make a list of the main sources of water pollution.
Industrial effluents
Agricultural wastes
14. Why are detergents unfriendly to the environment?
Detergents contain non-degradable materials which remain in the environment for a long time. Detergents in water bodies cause foaming and thus reduce the dissolved oxygen content of water. This is lethal to the aquatic organisms. Hence, detergents are unfriendly to the environment
15. Write a note on underground water pollution.
Closely associated with water pollution, is another serious problem
called underground water pollution. Pollutants like lead, arsenic and fluoride combine with hydrogen, oxygen, iron and chlorine in water and result in poisoning of ground water.
16. Write a note on Thermal pollution.
Many industries use high temperature furnaces and boilers in their manufacturing processes. The resulting hot effluents are directly released into a nearby water source. This is called Thermal pollution. It destroys the aquatic life due to the thermal shock.
17. Write a note on marine pollution.
Seas and oceans occupy about 71% of the earth. Most of the pollutants reaching the atmosphere condense and fall into these sources, causing marine pollution. Apart from this, agricultural runoff and industrial effluents also enter the sea. Oil seepage from huge tankers is another cause of marine pollution.
18. Suggest measures to Control water pollution.
1. Industrial effluents must be suitably treated to remove the pollutants. Toxic chemical substances must be eliminated. Acids and alkalis must be neutralized. Metallic compounds must be precipitated.
2. Effluents coming from furnaces must be cooled to room temperature and treated before being released.
3. Sewage water must be treated to remove suspended particles. It must be aerated and then chlorinated to purify water. This water can be reused.
19. List the sources of land pollution.
Land pollution is caused by litters, domestic wastes, trash, plastic items, agricultural runoff, and acid rain. Hazardous wastes from hospitals and industries, e-wastes, nuclear wastes, construction wastes and toxic chemicals.
20. Suggest measures to Control land pollution.
Soil pollution can be prevented by scientific management and safe disposal of solid wastes and hazardous materials. Some of the other measures include the following;
• Avoid buying packaged items which produce garbage.
• Buy biodegradable products.
• Create dumping ground away from residential areas.
• Do not litter on the ground and dispose the garbage properly.
• Use organic food that will be grown without the use of pesticides,
• Make people aware about the concept of 'Reduce, Recycle and Reuse’.
• Reduce the use of pesticides and fertilizers in agricultural activities.
21. What is noise? Write the major sources of noise pollution.
Undesirable sound is called noise. Sound above 100 decibels is called noise.
The sources of noise pollution
1. Vehicular traffic
2. Use of microphones and loudspeakers.
3. The gadgets used at home, like mixer and grinder.
4. Commercial and industrial activities.
5. Social and public events.

22. Same the chemicals that are harming the ozone layer that surrounds the earth.
The chief group of chemicals that is depleting the ozone layer is called chlorofluorocarbons (CFCs). The others include halons, methyl bromide, and methyl chloroform. In general, any chemical that releases either chlorine or bromine to the earth's atmosphere will harm the ozone layer.
23. What are chlorofluorocarbons? Name some of the uses of this group of chemicals.
Chlorofluorocarbons are a group of chemicals which contain atoms of carbon, fluorine and chlorine. Chlorofluorocarbons are used in many industries and products which include refrigeration industry, air conditioners, solvents, foam industry, inhalers and aerosols.
24. What is greenhouse effect?
The process of trapping of heat of the earth’s atmosphere due to excessive accumulation of certain gases like carbon dioxide, ozone and methane is called greenhouse effect.
25. What are greenhouse gases? Give examples.
Those gases which when present in the atmosphere of the earth in large excess will trap the sun’s heat and hence increase the temperature of the earth are known as greenhouse gases.
E.g. Carbon dioxide, ozone, methane, water vapour, oxides of nitrogen.
26. What is global warming?
Increase in the average temperature of the earth's atmosphere and oceans over a period of time due to excessive accumulation of certain gases like carbon dioxide and methane is known as global warming
27. Which one among the two given below is less toxic and why? (a) sulphurdioxide (b)lead vapour
Between sulphur di oxide and lead vapour the most toxic substance is lead vapour. This is because lead vapour is non-biodegradable and has a tendency to get accumulated in the human body causing harm. Sulphur di oxide is biodegradable and hence less harmful.
28. How is acid rain formed? What are its effects?
Oxides of sulphur and nitrogen in the atmosphere combine with water vapour and form sulphuric acid and nitric acid respectively. These precipitate as rain and come down as acid rain.
Effects of acid rain:
1. It affects all forms of life
2. It affects egg production in aquatic animals
3. It affects vegetation
4. Soil becomes acidic
5. It causes skin allergies and respiratory problem in humans
6. It affects old buildings and monuments.
29. Which is the main source of gases that cause acid rain?
Oxides of nitrogen and sulphur are known to cause acid rain. The main sources of these oxides are combustion of fossil fuels in automobiles and industries.
30. What is radiation?
The emission of energy as electromagnetic waves or as moving subatomic particles, especially high- energy particles which cause ionization is called radiation.
31. What is radiation pollution?
The contamination and degradation of the environment by the emission of high-energy electromagnetic waves or moving subatomic particles which cause ionization is called radiation pollution.
32. Which are the two types of radiation that can harm our environment?
The two types of radiation that can harm our environment are (i) ionizing radiation and (ii) non­ionizing radiation.
33. What is ionizing radiation? Give an example.
Radiation that has enough energy to remove one or more electrons from the orbit of an atom and thus make the atom become electrically charged or ionized is called ionizing radiation.
Ionizing radiation could be in the form of either waves or particles. Ionizing radiation in the form of waves includes X-rays and γ-rays. Those in the form of particles include α-particles and β-particles.
34. What is non-ionising radiation? Give examples.
Radiation that does not possess enough energy to remove electrons from the orbit of an atom and hence cannot cause ionization is known as non-ionizing radiation.
E.g. Light, heat etc.
35. Which are the sources of radioactive pollution?
Some of the principal sources of radioactive pollution are nuclear power plants, nuclear weapons, nuclear wastes, radioactive materials, radio-isotopes, and mining of radioactive materials
36. What are aerosols?
Aerosols are the Chlorofluorocarbons released during industrial processes involved in the manufacturing of insulating foams solvents etc.
37. Write a note on land pollution.
We are now using various kinds of materials in our day to day life. We follow a use and throw culture in our society. According to an estimate, every human generates about six kg of trash every day. In recent times, every billions of tons of cans, bottles and plastic items are being discarded. Only a small fraction of this is reused. The remaining is either burnt or dumped into open lands. Such places are now turning as breeding grounds for insects, rodents and other pests, apart from polluting the land.
In addition to this source, land pollution is also being caused by the agricultural runoff, containing residues of fertilizers and pesticides. Acid rain caused by air pollution, is also contributing to land pollution by altering the acidity and fertility of the soil.
38. Write a note on ozone depletion.
Ozone depletion is the reduction of the ozone in the stratosphere, about 15 to 60km. form the surface of Earth.
Depletion of ozone layer is due to the release of substances called chlorofluorocarbons (CFCs). It is a product of industrial processes involved in the manufacturing of insulating foams, solvents, cooling equipment’s like refrigerators and air conditioners. It is also found in various kinds of sprays that we use in our daily life, collectively known as aerosols. The ultra-violet rays in stratosphere break the CFCs into chlorine atoms. Chlorine reacts with ozone, breaks it into oxygen.
39. What is the effect of ozone depletion?
Thinning of the ozone layer allows high levels of UV radiation to reach the earth. This causes sudden changes called mutations in organisms.
· In human beings, the incidence of skin cancer and cataract increases.
· In plants and animals, it can affect growth and physiological functions.
· It affects the population ratio of phytoplankton causing serious imbalance in the ecosystem.
· In the atmosphere, it affects the natural balance of gases, particularly affecting the carbon cycle.
40. Write a note on global warming
Global Warming is an increase in the earth's atmospheric temperatures widely due to an increase in the greenhouse effect resulting especially from pollution.
Global warming is melting of ice from poles because of the increase in the extent of carbon dioxide. If due to global warming all the ice from our poles melt into water, the water level on earth increases and submerge the land.
Another major cause of global warming is deforestation.
Sea levels are expected to rise between 7 and 23 inches (18 and 59 centimetres) by the end of the century, and continued melting at the poles could add between 4 and 8 inches (10 to 20 centimetres). Less fresh water will be available. Species that depend on one another may become out of sync. For example, plants could bloom earlier than their pollinating insects become active. Natural calamities and disaster would occur at lesser frequencies and with more destructive power. Hurricanes and other storms are likely to become stronger. Severe heat waves would lead to death of millions of people all around the world. While the idea of swimming in a warmer ocean is pleasant to most human beings,increasing ocean temperatures could cause serious ecological damage.
41. Write the Sources of radioactive pollution.
· Nuclear power plants.
· Nuclear weapons.
· Disposal of nuclear wastes.
· Use of Radioactive isotopes.
· Mining and refining of radioactive substances like uranium and thorium.
42. Explain the natural greenhouse effect.
Greenhouse effect is a process by which thermal radiations is absorbed by atmospheric gasses and is reradiated in all directions. Part of this reradiated back towards the lower atmosphere. It results in an elevation of air surface temperature.
43. Pollution is caused in air, water and land.
44. Ozone depletion is due to the release of Chlorofluorocarbons.
45. One chlorine atom can destroy more than 1 lakh molecules of ozone.
46. Noise is measured in units called Decibels.
47. Oil seepage from tankers causes marine pollution.
48. Thermal pollution destroys aquatic life due to thermal shock.
49. Global warming is a process where the average temperature of earth’s atmosphere rises.
50. Green house is a process in which thermal radiations is absorbed by atmosphere and is reradiated in all directions.
51. Emission of Alpha particles, Beta particles and Gama rays causes pollution which is called radiation pollution.