The approach taken and conclusions reached by the Joint FAO-WHO Expert Committee on Food Additives.

The synthetic anabolic steroid trenbolone acetate (TBA) was evaluated by the Joint FAO-WHO Expert Committee on Food Additives (JECFA) in 1981, 1982, 1987 and 1989. Effects on reproductive function in rats were observed, with no-effect level of 0.5 mg TBA/kg diet. No evidence was found for a teratogenic potential of TBA in rats. From the results of in vitro as well as in vivo mutagenicity assays it was concluded that TBA was probably not genotoxic and that the increased tumour incidence observed in long-term studies in mice and rats arose as a consequence of the hormonal activity of TBA. The concentration of sex hormones in the circulation was significantly reduced and histopathological abnormalities (particularly in testes, ovaries and uteri) were observed in male and female pigs fed with high doses of TBA. The marginal no-effect level for these effects was 0.1 mg/kg diet, equal to approximately 2 micrograms/kg bw. The 34th JECFA meeting established an acceptable daily intake of 0-0.02 micrograms/kg bw of TBA.