2,3,7,8-Tetrachlorodibenzo-p-dioxin/Polychlorinated Biphenyls

TCDDs are formed as unintentional byproducts during the manufacture of chemicals and pesticides, bleaching of pulp and paper, and incineration of industrial and municipal waste. PCBs were produced commercially and used extensively as coolants and lubricants in transformers and other industrial equipment until their production and use were banned. These chemicals are still found in the environment and accumulate in the food chain, and can thus cause a number of adverse health effects, including reproductive and developmental problems, cancer, and damage to the immune system. Most of these toxic effects are mediated by the aryl hydrocarbon receptor. The toxicity of TCDD exhibits considerable interspecies variability.