Pollution.

Pollution is when something is added to the environment that is harmful or poisonous to living things. Smoke in the air from factories is a type of pollution, sewage in drinking water is another type of pollution.

Air pollution is caused by harmful gases such as carbon dioxide, sulfur dioxide, nitrogen dioxide carbon monoxide and very small particles of carbon. Most of the pollution is caused by factories, vehicles and livestock. Today air pollution has become dangerous to humans. Heavy air pollution may cause breathing problems such as asthma or other health problems.

Water pollution is the presence of harmful materials in water, such as sewage, dissolved metals, waste from farms and factories. Pollution causes harm to organisms living in water and can also harm people's health. In extreme cases it may cause problems such as cancer.

Soil pollution is when man-made chemicals, such as hydrocarbons, heavy metals, solvents, get into the soil. These chemicals come from industrial activities and from bad waste disposal. Soil pollution may cause health risks. The chemicals can produce harmful vapors, or they can contaminate water supplies underneath the polluted soil.

Sound pollution can cause ear problems or even permanent deafness, especially to older people. Noise pollution can also be defined as the unwanted and unpleasant sound present in the atmosphere.

The harmful noises in the environment, such as the sound of vehicles, loud speakers, etc. in a city is called noise pollution.