Morphological changes in monkeys consuming a diet containing low levels of 2,3,7,8-tetrachlorodibenzo-p-dioxin

Abstract Female rhesus monkeys given a diet containing 500 ppt (t = 10 12 ) 2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD) for 9 months became anaemic within 6 months and pancytopenic after 9 months of exposure. The marked thrombocytopenia was associated with widespread haemorrhage. Death occurred in five of the eight animals between months 7 and 12 of the experiment at total exposure levels of 2–3 μg TCDD/kg body weight. At autopsy, in addition to the extensive haemorrhage, there was a distinct hypocellularity of the bone marrow and lymph nodes. Hypertrophy, hyperplasia and metaplasia of the epithelium in the bronchial tree, bile ducts, pancreatic ducts, salivary-gland ducts and palpebral conjunctivae were observed. Squamous metaplasia and keratinization of the sebaceous glands and hair follicles were present in the skin. Death was attributed to complications from the severe pancytopenia.