Abstract:As an endocrine disruptor, dibutyl phthalate (DBP) has adverse effects on environment and human health. Using a polyclonal antibody of DBP, a sensitive indirectly competitive timeresolved fluorescence immunoassay(TRFIA) was proposed, and several parameters were investigated. DBP concentration in the rivers of Zhenjiang was determined, and the ecological risk was assessed by risk quotients. The results show that under the optimized conditions, the 50% inhibition concentration (IC50) value of TRFIA is 35.8 ng·mL-1 with limit detection value of 2.4 ng·mL-1 in the detection range from 4.7 to 272.6 ng·mL-1. The developed method shows high selectivity with crossreactivities less than 4.65% to seven structurally related phthalate esters. The recoveries are from 79.85% to 119.20%, and the reproducibilities of intraassay CV are from 5.54% to 9.93% with reproducibilities of interassay CV from 7.27% to 14.01%. The detection rate of DBP in the rivers of Zhenjiang city is 100%, and the concentration ranges from 5.89 to 94.57 ng·mL-1. There exists high ecological risk for DBP distribution in rivers.