This page on the epa.gov website provides some background about POPs (Persistent Organic Pollutants), the risks they present, and the global response to this group of toxic pollutants.

“Persistent organic pollutants (POPs) are toxic chemicals that adversely affect human health and the environment around the world. Because they can be transported by wind and water, most POPs generated in one country can and do affect people and wildlife far from where they are used and released. They persist for long periods of time in the environment and can accumulate and pass from one species to the next through the food chain.”