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 kraft pulp mill (BKPM) operations has increased in recent years to maximize resource use and to minimize residual environmental effects of discharged effluents. 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 estuarine killifish, Fundulus heteroclitus (mummichog). Comparison of data collected before (1997) and after (1998), the years of the process change, showed that the potential of the combined mill effluent to depress plasma testosterone levels after 30 and 57 d of exposure to an environmentally relevant effluent concentration (1%) was reduced after RO treatment of condensates. However, in vitro production of some sex steroids was depressed with a 1% effluent exposure after the process change. in addition, in 1998, depression of plasma testosterone levels in effluent-exposed fish was present at higher effluent concentrations (5%). These results are significant because they suggest that condensates may be a source of endocrine-disrupting compounds in BKPM effluents and RO may reduce their discharge.