Copyright © 2007 Dorling Kindersley
Pollution is waste that we put into the environment. It can harm plants and animals, including humans. Pollution comes from factories, and also from homes, farming, cars, ships, trucks, and aircraft. It includes smoke from fires, exhaust gases from engines, poisonous chemicals from industrial processes, rubbish such as plastic packaging, and sewage. These things pollute the landscape, rivers, lakes, seas, and the air. Noise and light can also be forms of pollution.
The city of Bangkok in Thailand is affected by smog – a mix of smoke and fog. It causes difficulties for people with breathing problems, such as asthma and bronchitis. Smoke from car engines, power stations, and factories is made up of waste gases, dust, and tiny particles of unburned fuel. These harmful waste gases include sulphur dioxide, nitrogen oxides, carbon dioxide, and carbon monoxide.
Some of the gases in the Earth’s atmosphere trap heat from the Sun. This is called the greenhouse effect, because the atmosphere works like the glass in a greenhouse. The greenhouse effect is natural, but pollution causes an increase in the gases that produce it, including carbon dioxide, water vapour, and methane.
Many trees are killed by acidic rain formed from pollutants in the air, especially sulphur dioxide and nitrogen oxides. These gases mix with water in the atmosphere to form rain that is acidic. Acid rain also kills aquatic life when it runs into ponds and lakes.
Leaks from oil tankers into the sea create oil slicks on the water surface. Where the oil reaches the shore, it covers beaches and kills seabirds.