Dioxin TCDD Finally Listed as ‘Known’ Human Carcinogen

BETHESDA, Md—An addendum to the National Toxicology Program’s Ninth Report on Carcinogens moves the dioxin TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) from the "reasonably anticipated" to cause human cancers category to the "known to be a human carcinogen" designation. A legal challenge to the change prevented the new designation from being published in the full report last May.

TCDD is present as a contaminant in some herbicides and pesticides, and it is formed as an inadvertent byproduct in the incineration of waste.