A BLEACHED-KRAFT MILL EFFLUENT FRACTION CAUSING INDUCTION OF A FISH MIXED-FUNCTION OXYGENASE ENZYME

Pulp mill effluents contain a myriad of chemicals that have the potent ial to cause deleterious effects on aquatic biota in receiving waters. Some of these chemicals evoke an acute lethal response of exposed bio ta while others evoke sublethal responses. One such sublethal response is the induction of mixed-function oxygenases (MFO) in fish, specific ally the CYPlA1 enzyme ethoxy-resorufin-o-deethylase (EROD). We follow ed the partitioning of the inducing chemicals in pulp mill effluent fr actions by Toxicity Identification Evaluation (TIE), or bioassay-drive n chemical analysis. This procedure was eventually modified to a more direct technique involving centrifugation, filtration, cleanup procedu res, and C-18 solid-phase adsorption. The extracts from the fractionat ion of two pulp mill effluents after secondary treatment were tested f or EROD-inducing activity in a 4-d rainbow trout bioassay. The methano l extracts of particulates/colloids showed significant inducing capaci ty in Mill A effluent but not in Mill B effluent. The C-18 methanol ex tracts induced activity from both effluents, with extracts from Mill A causing the greatest response. The particulate/colloidal extract (Mil l A) was used as the source material for chemicals which caused EROD i nduction. The fraction was purified by solid-phase extraction techniqu es and reverse-phase high-performance liquid chromatography. The major ity of the EROD activity was found in the moderately nonpolar region o f the chromatogram (K-ow = 4.6 to 5.1).