Technical pentachlorophenol: origin and analysis of base-insoluble contaminants.

A long history of toxicological problems has been associated with chlorinated aromatic compounds. Schulz (1) has given the clinical picture and an account of many episodes recorded since the initial description of chloroacne by Herxheimer in 1899. In addition to the history of human hazards, agriculture has been concerned with several episodes in which animal feeds were contaminated. Considerable losses of livestock in the 1950's were ascribed to the contamination of feed by chlorinated hydrocarbons. The nature of chick edema disease, responsible for the deaths of millions of broiler chicks in the late 1950's, has been the subject of a long series of chemical and toxicological studies. Chick edema disease is characterized by fluid accumulation in the hydropericardium among other symptoms. It had been suggested that the cause of the disease was a toxic factor present in fats added to the feed; however, its chemical nature was not elucidated until 1966, when 1,2,3,7,8,9hexachlorodibenzo-p-dioxin was identified by x-ray crystallography as a component of the factor isolated from toxic fats (2, 3). Toxic fats were originally recognized by a bioassay technique (4), since it was required