Persistent Organic Pollutants are a group of toxic chemicals that remain in the environment for long periods because they resist degradation. Their main features are:
Persistence: They do not break down easily under natural conditions.
Bioaccumulation: They concentrate in fatty tissues of living organisms.
Biomagnification: Their levels increase higher up the food chain.
Long-range transport: POPs can travel across borders through air and water, contaminating regions far from where they were released (including the Arctic).
Examples include dioxins, furans, polychlorinated biphenyls (PCBs), and banned pesticides such as DDT, aldrin, dieldrin, and heptachlor.
Because of their persistence and ability to move across borders, POPs are considered a global pollution problem, requiring international cooperation to manage. The first global agreement to control them was the Stockholm Convention on Persistent Organic Pollutants (2001). It initially targeted 12 chemicals, often called the “dirty dozen,” which include:
Nine pesticides (e.g., aldrin, chlordane, DDT, dieldrin, endrin, heptachlor, mirex, toxaphene, and hexachlorobenzene)
Two industrial chemicals (PCBs, hexachlorobenzene, counted also as pesticide)
Two groups of unintentional byproducts (dioxins and furans)
Since then, the list of POPs under regulation has expanded to include many more chemicals.