Endocrine responses of Fundulus heteroclitus to effluent from a bleached-kraft pulp mill before and after installation of reverse osmosis treatment of a waste stream

Implementation of process changes on the nonbleaching side of bleached kraf t pulp mill (BKPM) operations has increased in recent years to maximize res ource use and to minimize residual environmental effects of discharged effl uents. The objective of this study was to determine if reverse osmosis (RO) treatment of evaporator and digester clean condensates reduced or removed the effects of a BKPM effluent on reproductive endocrine function of the es tuarine killifish, Fundulus heteroclitus (mummichog). Comparison of data co llected before (1997) and after (1998), the years of the process change, sh owed that the potential of the combined mill effluent to depress plasma tes tosterone levels after 30 and 57 d of exposure to an environmentally releva nt effluent concentration (1%) was reduced after RO treatment of condensate s. However, in vitro production of some sex steroids was depressed with a 1 % effluent exposure after the process change. in addition, in 1998, depress ion of plasma testosterone levels in effluent-exposed fish was present at h igher effluent concentrations (5%). These results are significant because t hey suggest that condensates may be a source of endocrine-disrupting compou nds in BKPM effluents and RO may reduce their discharge.