Exposure to
dioxin and
dioxin-like compounds (DLCs) has been connected to the induction of
chloracne in humans and animals. 3,3',4,4'-Tetrachloroazobenzene (
TCAB) is an environmental contaminant that induces
chloracne in humans.
TCAB has been studied only to a limited extent in laboratory animals. While performing a 2-year gavage study in B6C3F1 mice to evaluate the toxic and carcinogenic effects of
TCAB, we also explored potential chloracnegenic properties. Groups of 50 male and 50 female B6C3F1 mice were exposed by gavage to
TCAB at dose levels of 0, 3, 10 and 30 mg/kg for 5 days a week for 2 years. The animals developed treatment-related gross inflammatory skin lesions, which were characterized histologically by
inflammation,
fibrosis,
hyperplasia, and
ulcers. Additionally, many of the animals developed follicular dilatation and sebaceous gland
atrophy, consistent with
chloracne-like lesions. This current 2-year study supports recently published papers showing susceptibility to
chloracne in mouse strains other than hairless mice. The
chloracne-like lesions were not clinically evident; therefore, our study highlights the need for careful examination of the skin in order to identify subtle lesions consistent with
chloracne-like changes in rodents exposed to
dioxin and DLCs. Since previous short-term studies did not demonstrate any skin lesions, we suggest that reliable assessment of all safety issues involving
dioxin and DLCs requires evaluation following chronic exposure. Such studies in animal models will help to elucidate the mechanisms of
dioxin-related health hazards.