In gavage studies, tetrabromobisphenol A caused an increase in the incidence of hepatoblastoma, hepatocellular carcinoma or hepatoblastoma (combined), haemangiosarcoma, and large intestine tumours in male mice, and induced uterine adenocarcinomas and rare malignant mixed Müllerian uterine tumours in female rats.12 Tetrabromobisphenol A interacts with human nuclear receptors, including thyroid-hormone receptor and PPAR-γ.13 It modulates enzymes relevant to the endocrine system, including aromatase, and is a potent inhibitor of oestrogen sulfotransferase.14,15 Tetrabromobisphenol A induces oxidative stress in human cells in vitro and in multiple species in vivo, and has immunosuppressive effects in human natural killer cells in vitro and in mice in vivo.16 A majority of Working Group members supported a group 2A classification based on "sufficient evidence of carcinogenicity in experimental animals", and strong mechanistic evidence. Pentachlorophenol and some related compounds Monograph Working Group Members C W Jameson (USA; Meeting Chair); I Linhart (Czech Republic); H U Käfferlein (Germany); G Ichihara (Japan); T Nomiyama (Japan); K Ogawa (Japan); H Kromhout (Netherlands); M van den Berg (Netherlands); M M Marques (Portugal); M A Abdallah (UK); R C Cattley (USA); A Ducatman (USA); J K Dunnick (USA); K W Hanley (USA); K Houck (USA); R Melnick (USA); F E Mirer (USA); S Nesnow (USA); A M Ruder (USA); J M Sanders (USA); K Steenland (USA); R T Zoeller (USA) Declaration of interests RM was involved in litigation on bladder cancer and exposure to p-cresidine and D-toluidine; KO is an employee of the Japanese Government; all other Working Group Members declare no competing interests Invited specialists D C Glass (Australia); T Sorahan (UK) Declaration of interests DCG has received funding from the Australian Institute of Petroleum; TS has received research awards from the rubber industry and the petroleum industry Representatives M Bisson (National Competence Centre for Industrial Safety and Environmental Protection; France) Declaration of interests All representatives declare no competing interests Observers S Borghoff (American Chemistry Council's North American Flame Retardant Alliance; USA); W Dekant (Bromine Science and Environmental Forum; Belgium); P Erkekoglu (Hacettepe University; Turkey); S Jacobi (Albemarle Europe SPRL; Belgium); O Manor (ICL-Industrial Products; Israel); V Thomas (University Paris Dauphine; France) Declaration of interests SB has provided research and consulting services for the North American Flame Retardant Alliance panel of the American Chemistry Council; WD has received financial support from the Bromine Science and Environmental Forum for a report on tetrabromobisphenol A and from the American Chemistry Council.