2,3,7,8-Tetrachlorodibenzo-p-dioxin which is often referred to simply as dioxin and is the reference for a number of compounds which are similar structurally and have dioxin-like toxicity. A substance extremely toxic to mammals, with a wide variation in sensitivity among species. Longer-term exposure of test mammals to lesser amounts can affect reproduction, cause birth defects, damage the liver and suppress the immune system. Several studies suggest that exposure to TCDD increases the risk of several types of cancer in people. Animal studies have also shown an increased risk of cancer from exposure to TCDD. The WHO and the USA DHHS have determined that TCDD is a human carcinogen. TCDD is a persistent environmental contaminant inadvertently produced as a by-product of herbicide and pesticide manufacturing. TCDD is also released during the bleaching process at tree pulp and paper mills, and during burning of municipal solid waste. Dioxins, like TCDD, have a long environmental half-life, bioaccumulate in the food chain, and can be found in human fat tissue, blood serum, breast milk and ovarian follicular fluid. TCDD is an aryl hydrocarbon receptor (AhR) agonist