In 1990, WHO recommended the TDI (Tolerable Daily Intake) of 10 pg/kg bw/day for dioxin. Since then, industrialized countries have set TDIs or exposure limits based on their own evaluation of the exposure levels and the toxicity of dioxin. In Japan, the MHW announced 10 pg TCDD/kg bw/day as the temporary TDI in 1996. WHO reevaluated the TDI in May 1998 and announced the TDI in the range of 1-4 pg TEQ/kg bw/day including coplanar PCBs, which will definitely have a big impact all over the world. Moreover, dioxins, as endocrine disrupting chemicals, are reviewed on their hazards on health and the mechanism of actions.