Persistent organic pollutants (POPs) are a class of chemicals that persist in the environment, are capable of long-range transport, bioaccumulate in human and animal tissue, and have significant impacts on human health and the environment. They include such substances as dioxin, PCBs, DDT, brominated flame-retardants or tributyltin (TBT). POPs released to the environment can travel through air and water to regions far distant from their original source.