Chloracne  (industrial acne) is an acneiform eruption due to poisoning by halogenated aromatic compounds with a specific  molecular shape.71  It is a syndrome characterized by the presence of facial comedones of various sizes not usually associated with inflammatory phenomena.72 Chloracnegens are listed in Table 3.4. Table 3.4   Known chloracnegens. Chloronaphthalenes (CNs) Polychlorinated biphenyls (PCBs) Polychlorinated dibenzofurans (PCDFs), especially tri-, tetra-, penta- and hexachlorodibenzofuran Contaminants of chlorophenols 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD)  Hexachlorodibenzo-p-dioxin  Tetrachlorodibenzofuran Chlorobenzenes  Crude trichlorobenzene  Crude benzene hexachloride The polychlorodibenzofurans and hexachloronaphthalenes may occur as contaminants and actually be the chloracnegens in some PCBs.

Tetrachlorozoxybenzene

  The degree  of halogenation does  not necessarily determine toxicity; the position of the halogen atoms on the outside of the molecule is however vital. Therefore, complete details of the nature and quantity of the various isomers in any single chloracnegen is essential before any prediction of its possible  toxicity  can be made. Chloracne has also been caused, uncommonly, by brominated biphenyls.