"Manufacturers have been adding the germ fighter triclosan to soaps, hand washes, and a range of other products for years. But here’s a dirty little secret: Once it washes down the drain, that triclosan can spawn dioxins.
Dioxins come in 75 different flavors, distinguished by how many chlorine atoms dangle from each and where those atoms have attached (their locations indicated by the numbers in the front part of a dioxin’s name). The most toxic is 2,3,7,8-tetrachlorodibenzo-p-dioxin, or TCDD. Some related kin bearing four to eight chlorines are also toxic, just less so.
Triclosan’s dioxin progeny belong to this infamous family, but aren’t the ones that have typically tainted the environment. And, before you ask: No one knows how toxic triclosan’s dioxins are. Few investigations have been conducted because chemists considered them arcane and too rare to pose a threat."