What are the three main causes of water pollution ?

The three main causes of water pollution are :

1. Domestic sewage — Water discharged from our homes contains dirt from excreta of the toilet, washing of clothes, utensils and food and vegetable waste. It is called sewage. It is drained off into the lakes, rivers and seas. It contains microorganisms which spread jaundice, cholera, typhoid, etc.
2. Agricultural waste — Pesticides, insecticides and fungicides used in the fields are washed away by rain water into rivers. These chemicals harm aquatic life and spoil the human food.
3. Industrial waste — The waste chemicals from industry, called effluents, get dissolved in water bodies and are toxic to aquatic plant and animal life. They make water unfit for human consumption as well.