TCDD, or 2,3,7,8-tetrachlorodibenzo-p-dioxin, is a toxic chemical compound that belongs to a group of substances known as dioxins. It is primarily a byproduct of industrial processes, such as the production of herbicides and the burning of waste. TCDD is known for its persistence in the environment and can accumulate in the food chain, particularly in fatty tissues of animals. Exposure to TCDD can have serious health effects, including immune system suppression, reproductive issues, and an increased risk of certain cancers. Due to its toxicity, TCDD is classified as a persistent organic pollutant (POP) and is subject to international regulations aimed at reducing its release into the environment.