Surface runoff, also called nonpoint source pollution, from a farm field in Iowa, the United States during a rainstorm. Topsoil, as well as farm fertilizers and other potential<unk> s, runoff unprotected farm fields when heavy rains occur.|400x400px A<unk>  is a substance or energy introduced into the environment that has undesired effects, or adversely affects the usefulness of a resource. A<unk>  may cause long- or short-term damage by changing the growth rate of plant or animal species, or by interfering with human amenities, comfort, health, or property values. Some<unk> s are biodegradable and therefore will not persist in the environment in the long term. However, the degradation products of some<unk> s are themselves polluting such as the products DDE and DDD produced from the degradation of DDT.
Pollutant
Pathogen
Pesticide
Designer drug
Biological agent
Toxic waste
Toxicant
Inhalant