Many pulp and paper mills use chlorine-based chemicals to bleach pulp white. These chemicals react with organic molecules in the wood and other fibers to create many toxic by-products, including dioxin. Dioxin is found throughout the pulp and paper manufacturing process, its wastes and even in the paper products themselves.
Pulp mills use large quantities of water to wash process chemicals off the paper fibers.
This water contains many pollutants, including dioxin in mills using chlorine-based bleaching. Also, since dioxin doesn't easily break down in the environment, the dioxin released builds up in the river, lake or ocean sediments near the pulp mills, and concentrates in the food chain. Because dioxin persists and magnifies in the foodchain, it can be hundreds of times more concentrated in fish than in the water they live in. An EPA study, the National Study of Chemical Residues in Fish, found that fish near chlorine-bleaching pulp and paper mills have significantly higher dioxin concentrations than anywhere else that's been tested. Although we can expect lower dioxin levels in waters and fish after these changes, some will still be there.