Persistent organic pollutants stay in the environment for long periods of time. They also are easily spread, by water and wind. And they can pass from one life form to another, all up and down the food chain. So their effects are not only long-lasting, but also widespread. For they can end up way far away from where they were originally used. The most common, and most lethal, are known as the dirty dozen. The dirty dozen have had great appeal, at different times. For they have tended to be part of products that get the job done [such as insecticidces] or key players in industry. So aldrin, chlordane, DDT, dieldrin, endrin, heptachlor, mirex, and toxaphene have been spread by the rampant use of insecticides. Hexachlorobenzene has been spread through fungicide treatments of seeds. Like PCBs, it has also been spread industrially. It's necessary to the making of ammunition, fireworks, and synthetic rubber. PCBs are integral to electrical capacitors and transformers. Like dioxins and furans, hexachlorobenzene and PCBs also are produced anytime there is a burn.