NIOS Class 12 Environmental Science Chapter 11
INTEXT QUESTIONS 11.1
1. Define health.
Ans: The Health of a person is the result of the interaction of a large number of influences upon the person.
2. What is the advantage of providing potable water (drinking water) to the community?
Ans: Providing potable water to the community prevents the spread of water-borne diseases.
3. What are slums?
Ans: Slums are unplanned aggregations of hutments arranged very closely without any space for roads, parks, drains, etc.
4. State any two reasons for health problems in villages?
Ans:
- One of the major problems of the villages is the lack of a safe drinking water supply.
- Improper disposal or lack of disposal of excreta adds to the sanitation problems.
- High infant mortality rate and low life expectancy.
- Rural households are not properly ventilated. As a result, they suffer from a lack of fresh air, and many rural households are single-room units which get filled with smoke from burning firewood and biomass and do not get adequate sunlight.
- The lack of proper drainage leads to contamination of groundwater and other sources of drinking water.
INTEXT QUESTIONS 11.2
1. State one example of a disease transmitted by a vector.
Ans: Mosquitoes spend a part of their life cycle in water. Vector for diseases such as malaria, yellow fever, encephalitis, filaria and dengue.
2. Diarrhea with or without blood or mucous in stools, fever and gripping pain in the abdomen are all symptoms of a wwater-borne aliment. Name it.
Ans: Bacterial dysentery
3. Name the bacteria which cause Leptospirosis.
Ans: Leptospira
INTEXT QUESTIONS 11.3
1. From which industries are foul-smelling gases released.
Ans: Sugar mills and tannery industries.
2. Which air pollutant is released from stone quarries and iron mines?
Ans: Suspended particulate matter.
3. In congested townships, movement of traffic on dusty roads, smoke from industries and diesel vehicles result, a pollutant gathering in the air. Which pollutant is it?
Ans: Oxides of sulphur, oxides of nitrogen, hydrocarbons, carbon monoxide, carbon dioxide.
4. List the major pollutants in agricultural areas.
Ans: Ammonia, pesticides, smoke and water vapour.
INTEXT QUESTIONS 11.4
1. Name three pesticides which are known to cause lymphatic cancer in rats and mice.
Ans: Toxaphene/hexachlor cyclohexane – HCH, BHC, dieldrin, DDT (any three)
2. What measures can be taken to minimize the incidence of skin cancer?
Ans: Avoiding exposure to direct midday sunlight (from 10 a.m. to 3 p.m.) is perhaps the best way of reducing the risk of skin cancer. Wearing a broad-brimmed hat, the use of UV-absorbing sunglasses and clothing to cover the body adequately also offers protection against UV.
3. What are the possible programmes which can be taken up to minimize damage from pesticides?
Ans: Organic farming and Integrated Pest Management (IPM).
4. What is the cause of the Blue Baby Disease?
Ans: When water containing nitrates is consumed, and it reaches the intestines, the intestinal bacteria convert nitrates into nitrites. The nitrite ions combine with hemoglobin to form methemoglobin, which inhibits the oxygen-carrying capacity of the blood, causing a kind of anemia known as methemoglobinemia. Methemoglobin is formed when iron in the hemoglobin molecule is oxidized from Fe2+ (ferrous) to Fe3+ (ferric) form. Due to reduced oxygen carrying capacity, the babies gradually acquire a blue tinge and hence the name – “Blue Baby disease”.
5. Give two major symptoms of Asthma.
Ans: Shortness of breath, wheezing, chest lightness, pain around the chest, persistent cough that can last several weeks (any two).
INTEXT QUESTIONS 11.5
1. What is heavy metal toxicity?
Ans: Toxic metals are dispersed in the environment through industrial effluents, burning of organic wastes, transport and power generation. It may endanger public health after being incorporated into the food chain.
2. State two symptoms of arsenic poisoning due to the consumption of groundwater containing arsenic.
Ans: Loss of appetite, loss of weight, diarrhea, gastrointestinal disturbance, and skin cancer. (any two)
3. Mention the form in which mercury acts as a poison.
Ans: Methyl mercury.
4. Which metal does battery scrap leave in the environment?
Ans: Lead (Tetraethyl lead TEL)
INTEXT QUESTIONS 11.6
1. Which workers are involved with heavy physical work?
Ans: Miners, lumberjacks, construction workers, farmers, fishermen, storage workers and health care personnel.
2. What kind of problem does a sound level of 120 dB for a few hours lead to?
Ans: Annoyance, disturbed sleep, lack of concentration, reduced efficiency, temporary hearing loss, and disturbed sleep.
3. State any two symptoms of long exposure to noise pollution?
Ans: Auditory fatigue, deadness or impaired hearing, blood pressure, breathing and sweating, giddiness. (any two)
TERMINAL EXERCISE
1. What are some of the sanitary problems in villages?
Ans:
- Lack of proper toilets and improper disposal of human waste lead to improper sanitary conditions and health hazards.
- Poor drainage or improper drainage results in the accumulation of wastewater in public places.
- Animal excreta and movement of cattle in and out of water pools and puddles spread this filth over larger areas, further causing sanitary problems.
2. Describe the transmission of the following diseases: Typhoid, Filaria (Elephantiasis), and Amoebic dysentery. What is the causative organism for each of these diseases?
Ans:
- Typhoid: Caused by Helminthes (parasitic worms) through the domestic water supply.
- Filaria (Elephantiasis): Caused by Wuchereria through mosquitoes.
- Amoebic dysentery: Caused by Entamoeba histolytica via the ingestion of cysts in food or water.
3. Describe a disease often prevalent in coal miners working for many years. State the measures required to control it.
Ans: Black lung disease, called pneumoconiosis (CWP). The deposits of coal dust make miners’ lungs look black instead of a healthy pink, and hence the name black lung disease. The particles of fine coal dust accumulate in the lungs as they cannot be destroyed within the lungs or removed from them. Eventually, this build-up causes thickening and scarring, making the lungs less efficient in supplying oxygen to the blood.
The only way to prevent black lung disease is to avoid long-term exposure to coal dust. Coal mines may help prevent this condition by lowering the coal dust level and providing protective clothing to coal miners.
4. What are some of the major pollutants from a thermal power plant? What can be done to minimize these?
Ans: Nitrogen oxide and sulphur dioxide are the major pollutants from thermal plants. They can be controlled by using low-sulphur fuels to generate heat and also by installing electrostatic precipitators.
5. Describe the symptoms of arsenic poisoning from drinking polluted groundwater. In which parts of the body can arsenic accumulation be detected?
Ans: If a person drinks water contaminated with arsenic for about 10 years, dark spots develop on the upper chest, back, and arms, known as melanosis. The next stage is keratosis, in which palms become hard, and the patient may suffer from diarrhea, stomach pain, breathing problems, etc. Later, along with dark spots, white spots develop, legs become swollen, and walking becomes difficult and painful; some wounds start bleeding, and the liver and kidneys suffer damage. Arsenic accumulation can be detected in hair and nails.
6. Discuss the problems caused in infants by high nitrate concentration in drinking water.
Ans: When water containing nitrates is consumed, and it reaches the intestines, the intestinal bacteria convert nitrates into nitrites. The nitrite ions combine with hemoglobin to form methemoglobin, which inhibits the oxygen-carrying capacity of the blood, causing a kind of anemia known as methemoglobinemia. Methemoglobin is formed when iron in the hemoglobin molecule is oxidized from Fe2+ (ferrous) to Fe3+ (ferric) form. Due to reduced carrying oxygen capacity, the babies gradually acquire a blue tinge and hence the name – “Blue Baby disease”.
7. List auditory and non-auditory problems caused by too much noise.
Ans: Auditory effects
- (i) Auditory fatigue – Occurs when the noise level is in the range of 85 to 90 dB, e.g. noise of a food blender.
- (ii) Temporary or permanent deafness or impaired hearing. Temporary hearing loss occurs from continuous noise exposure, which disappears within 24 hours after a period of rest. Repeated or continuous exposure to noise more than 90 dB may result in permanent loss of hearing.
Non-auditory effects
- (i) High level of noise interference with speech and communication. Here, one needs to strain his voice by increasing loudness to make speech intelligible. Street hawkers or salesmen of small stalls in busy markets need to yell continuously at the top of their voice so that they are heard. Due to this, they suffer from voice disorders or even cancer of the voice box later in life.
- (ii) Annoyance: Most people are annoyed by noise, and some may become neurotic. Neurotic people lose their temper quickly and become irritable.
- (iii) A high level of noise in the workplace reduces working efficiency. A quiet environment helps in increasing efficiency.
- (iv) Exposure to noise increases blood pressure, pulse rate, breathing and sweating or headache. Giddiness, nausea, fatigue, disturbed sleep, distorted colour perception and reduced night vision are general symptoms observed in victims of noise. People working night shifts or those suffering from hypertension are affected by noise earlier than others.
8. Discuss the significance of addition of tetraethyl lead to petrol. Why has the use of leaded petrol been discontinued?
Ans: Tetraethyl lead (TEL) was added to petrol as an anti-knock agent for the smooth running of automobile engines. It causes lead to enter the atmosphere from automobile exhaust. Lead in petrol is being phased out by the introduction of lead-free petrol. TEL has now been replaced by other anti-knock compounds to prevent the emission of lead by automobiles.
9. How does a cancerous tumour differ from a non-carcinogenic tumour?
Ans: The tumours can be either benign or malignant.
- The benign tumours are not harmful and can be removed surgically, and do not reappear. Further, cells from these tumours do not move to other parts of the body and rarely endanger life.
- Malignant tumours are cancerous. Cells of these tumours are abnormal, and they divide and re-divide without any control. They can invade and damage nearby tissues and organs. Cells from these tumours can break away and enter the bloodstream or lymphatic system and spread from the original site to form new tumours in other organs.
10. What are some of the major effects of smoking and chewing tobacco?
Ans:
- Smoking may increase the chances of getting cancers of the stomach, liver, prostate, colon and rectum.
- Use of smokeless tobacco, chewing tobacco and snuff causes cancer of the mouth and throat.
- Exposure to environmental tobacco smoke, termed passive smoking, also increases the risk of lung cancer for non-smokers.
- The risk of cancer begins to decrease soon after quitting smoking and chewing tobacco. This risk continues to decline gradually after quitting.
Additional Study Materials
- Chapter 6 Natural Ecosystem
- Chapter 7 Human Modified Ecosystems
- Chapter 8 Human Societies
- Chapter 10 Environmental Pollution
