Abstract:A screening level risk assessment model (the risk assessment identification and ranking) was introduced and used to evaluate the potential ecological risk of 2,3,7,8-TCDD and OCDD in Beijing area. These chemicals were binned into categories of similar probable risk accordingly. The simulation results showed that if dioxins emitted into the atmosphere, water and soil proportionally as they were and the objective endpoints were applied, the risk assessment factor (RAF) were 235 and 0.246 for 2,3,7,8-TCDD and OCDD, respectively. These two chemicals were binned into A and C category based on the RAF values. Moreover, if the effect endpoints were applied, the RAFs were 6.70×10-3 and 1.11×10-3, respectively. 2,3,7,8-TCDD and OCDD were classified into D category. The potential ecological risk of other dioxin congeners were expected to fall between 2,3,7,8-TCDD and OCDD, accordingly.