List two major harmful effects of each of the following:

(i) Rivers contaminated with sewage.

(ii) Too much gaseous exhausts containing CO₂ and SO₂.

(iii) Pesticides such as DDT used in agriculture.

(iv) Prolonged noise such as the one produced by crackers throughout the night.

(i) Rivers contaminated with sewage.

1. A polluted river gives rise to several water-borne diseases that affect both humans as well as animals.

2. The aquatic life - flora and fauna - is adversely affected.

(ii) Too much gaseous exhausts containing CO₂ and SO₂.

1. SO₂ is responsible for acid rain.

2. The high concentration of carbon dioxide in the atmosphere contributes to greenhouse effect which in turn leads to global warming.

(iii) Pesticides such as DDT used in agriculture.

1. Pesticides also kill essential soil microbes. Their microbes are required for recycling the soil nutrients.

2. Pesticides can enter the food chain. This will lead to health complications in humans.

(iv) Prolonged noise such as the one produced by crackers throughout the night.

1. The consistent exposure to high decibels can severely damage the eardrums. This will lead to hearing impairments.

2. Noise pollution, in general, gives rise to headaches and lack of concentration.