Question

Which one of these does NOT cause water pollution?
1. The construction of dams across rivers
2. Floating of dead bodies of cattle down the river
3. The removal of desirable substances from water-bodies
4. The addition of undesirable substances to water-bodies

Answer 1

Correct Answer - Option 1 : The construction of dams across rivers

The correct answer is The construction of dams across rivers.

• The contamination of water with unwanted and harmful substances in water adversely affects the living organism is called water pollution.
• Water pollution covers the following causes:
  • The addition of undesirable substances to water bodies. 
    •  These substances could be the fertilizers and pesticides used in farming or they could be poisonous substances, like mercury salts which are used by paper industries.
    • These could also be disease-causing organisms, like the bacteria which cause cholera.
    • Floating of dead bodies of cattle down the river leads to disease-causing organisms.
  • The removal of desirable substances from water bodies. 
    • Dissolved oxygen is used by the animals and plants that live in water.
    • Any change that reduces the amount of this dissolved oxygen would adversely affect these aquatic organisms.
    • Other nutrients could also be depleted from the water bodies.
  • A change in temperature.
    •  Aquatic organisms are used to a certain range of temperature in the waterbody where they live, and a sudden marked change in this temperature would be dangerous for them or affect their breeding.
    • The eggs and larvae of various animals are particularly susceptible to temperature changes.
• The best way to prevent large-scale water pollution is to try and reduce its harmful effects.
• There are various small changes we can make to protect ourselves from a scary future where water is scarce.
  • Save Water
  • Better treatment of sewage
  • Use environmentally friendly products

• Effects of Water Pollution on Human Health:
  • Domestic and hospital sewage contain many undesirable pathogenic microorganisms, and its disposal into the water without proper treatment may cause an outbreak of serious diseases, such as typhoid, cholera, etc.
  • Metals like lead, zinc, arsenic, copper, mercury, and cadmium in industrial wastewaters adversely affect humans and other animals.
  • Consumption of such arsenic polluted water leads to accumulation of arsenic in the body parts like blood, nails, and hairs causing skin lesions, rough skin, dry and thickening of the skin, and ultimately skin cancer.
  • Mercury compounds in wastewater are converted by bacterial action into extremely toxic methyl mercury, which can cause numbness of limbs, lips, and tongue, deafness, blurring of vision, and mental derangement.
  • Pollution of water bodies by mercury causes Minamata (neurological syndrome) disease in humans.
  • Lead causes lead poisoning (Lead interferes with a variety of body processes and is toxic to many organs and tissues).
  • The compounds of lead cause anemia, headache, loss of muscle power, and bluish line around the gum.
  • Water contaminated with cadmium can cause itai-itai disease also called ouch-ouch disease (a painful disease of bones and joints) and cancer of the lungs and liver.