Dioxins have never been produced intentionally. They may be formed as unwanted by-products in a variety of industrial and combustion processes, including household
fires. Most industrial releases of dioxins are strictly controlled under pollution prevention and control regulations.
Dioxins and PCBs from these sources may be released in small quantities into the air, water or land. Animals and fish then take
them up from their food and any soil and sediment they take in while they are feeding. The chemicals are absorbed into their body fat, where they accumulate.