Persistent organic pollutants (POPs) are organic compounds of natural or anthropogenic origin that resist photolytic, chemical and biological degradation. They are characterized by low water solubility and high lipid solubility, resulting in bioaccumulation in fatty tissues of living organisms. POPs are transported in the environment in low concentrations by movement of fresh and marine waters and they are semi-volatile, enabling them to move long distances in the atmosphere, resulting in wide-spread distribution across the earth, including regions where they have never been used. Thus, both humans and environmental organisms are exposed to POPs around the world, in many cases for extended period of time.
United Nations Environment Programme