Environmental chemicals in drinking water can impact human health through nuclear receptors.Additionally,estrogen-related receptors(ERRs)are vulnerable to endocrine-disrupting effects.To date,however,ERR disruption of drinking water potency has not been reported.We used ERRγ two-hybrid yeast assay to screen ERRy disrupting activities in a drinking water treatment plant(DWTP)located in north China and in source water from a reservoir,focusing on agonistic,antagonistic,and inverse agonistic activity to 4-hydroxytamoxifen(4-OHT).Water treatment processes in the DWTP consisted of pre-chlorination,coagulation,coal and sand filtration,activated carbon filtration,and secondary chlorination processes.Samples were extracted by solid phase extraction.Results showed that ERRγ antagonistic activities were found in all sample extracts,but agonistic and inverse agonistic activity to 4-OHT was not found.When calibrated with the toxic equivalent of 4-OHT,antagonistic effluent effects ranged from 3.4 to 33.1 μg/L.In the treatment processes,secondary chlorination was effective in removing ERRy antagonists,but the coagulation process led to significantly increased ERRγ antagonistic activity.The drinking water treatment processes removed 73.5% of ERRγ antagonists.To our knowledge,the occurrence of ERRγ disruption activities on source and drinking water in vitro had not been reported previously.It is vital,therefore,to increase our understanding of ERRy disrupting activities in drinking water.