Comparing biological responses to mill process changes: A study of steroid concentrations in goldfish exposed to effluent and waste streams from a Canadian bleached sulphite mill

Abstract

During the cycle 1 environmental effects monitoring (EEM) studies, wild fish collected downstream of several Nexfor Canadian pulp mills indicated reduced gonad size or fecundity. A two-year collaborative study between Nexfor Inc. and the National Water Research Institute of Environment Canada was begun to investigate the reproductive responses. The purpose of the study was to assess final effluents from Nexfor Canadian mills for their ability to affect goldfish circulating sex steroids (testosterone, 11-ketotestosterone) or production of steroids in vitro by testes from exposed fish. Along with final effluent, individual waste streams from the mill processes were tested to investigate the potential source(s) of steroid-disrupting compounds from within the mill. The study also provided a chance to study effluent potencies over time as mill processes were changed and upgraded. Goldfish exposed for 16-21 days to final effluent (100%) from a bleached sulphite mill (BSM) showed reduced testosterone and 11-ketotestosterone production by testes. Testes of goldfish exposed to undiluted final effluent had steroid production one-tenth that of controls. Fish exposed to individual waste streams (2-40%) had steroid production similar to control fish. It was difficult to assess the waste streams, as fish-exposure concentrations were inconsistent among waste streams due to differences in the acute toxicity of streams. Final effluent from the same mill collected one year later, after numerous mill upgrades (such as changes in chip handling, digester operation and better control of spills), showed an improvement: Goldfish exposed to 100% effluent had normal steroid levels. The study demonstrates the use of the goldfish steroid bioassay for detecting changes in effluent quality. Changes in processes at the mill in the year following the fish tests resulted in final effluent that had no deleterious effects on fish testes production of steroids. The environmental consequences resulting from the improvement in BSM final effluent quality will be tested during the cycle 2 EEM.