Waste by-products are chemicals produced and released unintentionally into the environment by combustion or some chemical processes. Dioxins, a class of POPs, are by-products of waste incineration, chemical and pesticide manufacturing, and pulp and paper bleaching. The most potent dioxin, 2,3,7,8-TCDD, is a known human carcinogen.
Some persistent organic pollutants (POPs) are by-products that were produced unintentionally and released to the environment during combustion or during some chemical processes. For example, dioxins, furans, alpha-HCH, and beta-HCH are never intentionally produced (except for laboratory purposes). Dioxin, for example, one of the original "Dirty Dozen" of the Stockholm Convention, is typically produced during incineration. Two others, PCBs and HCB, are produced both intentionally and unintentionally.