Pollution refers to both the process of introducing contaminants into the environment and the contaminating matter or toxin. In terms of the environment, the main types of pollution are air, water and soil pollution.
Light and noise pollution are other examples, but these issues primarily impact human society rather than the natural world. Pollution is usually the result of human activity and has the effect of making the environment unsafe or undesirable for living things. Pollution is a primary topic of study for students of environmental science and ecology. This topic is also the source of health concerns, activist interest, and legal and political debate.