Effects of Pollution
ICSE Class 9 · Geography · Chapter 18
What this chapter covers
- How pollution causes harm
- Effects of air pollution on the environment
- Effects of water pollution on the environment
- Effects of soil pollution on the environment
- Effects of radiation and noise pollution on the environment
- Effects of pollution on human health
- Health effects of air pollution
- Health effects of water and soil pollution
- Health effects of radiation and noise pollution
- Comparing the effects of pollution
Key points
- An effect of pollution is any harmful change in the environment or in human health that a pollutant causes; the two groups of effects are closely linked.
- Acute effects appear quickly after a large exposure; chronic effects build up slowly over months or years and are often more serious.
- The harm a pollutant does depends on its concentration, the length of exposure and the sensitivity of the person, plant or animal exposed.
- Air pollution reduces visibility, damages plants and crops, makes rain acidic, stains and corrodes monuments such as the Taj Mahal, harms animals and is linked to rising temperatures.
- In fresh water, sewage uses up dissolved oxygen and kills fish, nutrients make weeds choke lakes, and industrial waste adds heavy metals that poison water and fields.
- In the sea, oil spills kill birds and fish, plastic is swallowed by turtles and seabirds, and coral reefs, fishing and tourism suffer.
- Soil pollution lowers fertility, kills earthworms and soil bacteria, passes poisons along the food chain and spreads into water.
- Radioactive fallout contaminates land, water and food for many years and causes mutations that affect later generations.
- Noise disturbs birds and animals, drives wildlife away and its vibrations can crack old buildings.
- Polluted air causes asthma, bronchitis, lung cancer, heart disease, carbon monoxide poisoning and eye irritation; PM2.5 is the most harmful part.
- Polluted water causes cholera, typhoid, diarrhoea and jaundice, and chemical poisoning by mercury, lead and arsenic.
- Polluted soil and food cause illness through pesticide residues, and bio-medical waste spreads infections such as hepatitis B.
- Radiation causes radiation sickness, cancer, especially leukaemia and thyroid cancer, and birth defects; X-rays are safe when the dose is controlled.
- Noise above about 85 dB for long periods causes permanent hearing loss, and noise also raises stress, blood pressure and loss of sleep.
Questions answered
Define an effect of pollution and state the two broad groups into which the effects of pollution are divided.
An effect of pollution is any harmful change in the air, water, soil, plants, animals, buildings or human health caused by a pollutant. Effects are divided into effects on the environment and effects on human health.
Distinguish between acute and chronic effects of pollution, giving one example of each.
Acute effects appear quickly after a large exposure, for example fish dying the morning after a factory discharge. Chronic effects develop slowly over months or years of smaller exposure, for example lung disease in a person living beside a busy highway for many years.
How does dust from a factory affect the plants growing near it?
The dust settles on the leaves and blocks the stomata, and it also cuts off sunlight. The plant makes less food, grows slowly and gives a lower yield.
Why has the marble of the Taj Mahal turned yellowish in places, and what step has been taken to protect it?
Carbon particles and dust from vehicles, industries and the burning of fuel and waste settle on the marble and stain it, and acidic gases slowly corrode it. The Taj Trapezium Zone has been created around the monument, in which polluting industries and fuels are strictly controlled.
Explain why the discharge of sewage into a river causes the death of fish.
Bacteria in the river break down the sewage and use up the dissolved oxygen as they do so. When the oxygen level falls below about 4 mg per litre, fish cannot breathe and they die or move away.
State two effects of an oil spill on marine life.
Oil coats the feathers of seabirds so that they cannot fly or keep warm, and it blocks sunlight from plankton and smothers mangrove roots and coral, killing fish and other sea animals.
Give two effects of the excessive use of chemical fertilisers on soil.
The soil loses its humus and becomes hard and compact, and its natural fertility falls, so more fertiliser is needed each year for the same crop. Fertiliser washed from fields also pollutes nearby ponds and lakes.
Why are the effects of radioactive fallout said to last for generations?
Some radioactive substances remain dangerous for many years, so land, water and food stay contaminated. Radiation also causes mutations in reproductive cells, which are passed on to the next generations as birth defects.
Past board exam questions
ICSE 2019 sample paper · 2 marks
(i) What is the cause of ozone depletion? (ii) State the impact of ozone depletion on human life.
Show answer
(i) Ozone depletion is caused mainly by chlorofluorocarbons (CFCs) released from refrigerators, air conditioners, aerosol sprays and foam, and by halons and nitrogen oxides; chlorine from them breaks down ozone molecules in the stratosphere.
(ii) More ultraviolet rays reach the Earth, causing skin cancer, cataract (eye damage) and weakening of the immune system in human beings.
ICSE 2019 sample paper · 2 marks
Which health hazards are associated with radioactive waste?
Show answer
Radiation from radioactive waste can cause cancer (e.g. leukaemia, skin cancer), genetic mutations and birth defects in children, damage to body tissues and organs, burns, sterility, and even death on heavy exposure.