Pollutant

A pollutant is substance or energy introduced into the environment that has undesired effects, or adversely affects the usefulness of a resource. A pollutant 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. Pollutants may be classified by various criteria: (1) By the origin: whether they are natural or man-made (synthetic). (2) By the effect, regardless of origin: on an organ, specie, or ecosystem. (3) By the properties: mobility, concentration, persistence, toxicity. (4) By the controllability: ease or difficulty of removal. Some pollutants are biodegradable and therefore will not persist in the environment in the long term. However the degradation products of some pollutants are themselves polluting such as the products DDE and DDD produced from degradation of DDT.