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As part of a continuing survey, effluents from five mills in Canada were tested in the laboratory for their potential to affect fish reproduction. The study included effluents from two thermomechanical pulp (TMP) mills, two kraft pulp mills, and one mill that used both chemical and mechanical pulping. The laboratory test used adult fathead minnows and involved a 21-day exposure to each effluent. All the effluents were tested at 2 and 20% concentration. The effluent from 1 of the kraft mills was also tested at 40% concentration. The endpoints of the test included, egg production, gonad size, sex steroids, secondary sexual characteristics, and vitellogenin concentration in males, considered to be an indicator of estrogenicity. The results of this study were similar to the results of our previous survey. None of the effluents produced noteworthy changes at 2% concentration. At 20% concentration, only the effluent from the multiprocess mill produced a significant reduction in eggs, which was considered to be the most important indicator of reproductive performance. Some effluents did produce an increase and/or a decrease in a variety of endpoints other than egg production, but the most consistent response was an induction of vitellogenin in males exposed to three of the five effluents tested. In summary, these results indicate that most mill effluents up to 20 or 40% concentration do not affect the overall reproductive capacity of minnows in the laboratory. However, the mill effluents do seem to contain substances that cause vitellogenin induction. [ABSTRACT FROM AUTHOR]

In Canada, effluents from pulp and paper mills are regulated for toxicity. The regulation requires ≤50% survival of rainbow trout (Oncorhynchus mykiss) exposed to full-strength (i.e., 100%) effluent for 96 h in tests that must be conducted monthly. The regulation also calls for ≥50% survival of Daphnia magna exposed to 100% effluent for 48 h in weekly monitoring tests. Every year, about 10 to 25% of the mills exceed the regulatory limit at least once in tests with either rainbow trout or Daphnia magna. Between 1996 and 2003, we investigated 84 such cases from 32 mills. Of the 84 investigations, 49 involved only trout, 29 involved only Daphnia, and six involved both species. We identified the actual cause of toxicity in 70% of the cases and partially or tentatively identified the toxicant(s) in 17% more. In the cases involving only trout, the most frequent causes of toxicity were related to biotreatment performance (e.g., ammonia). In the cases involving only Daphnia, the most frequent cause of toxicity seemed to be related to polymeric formulations. For those cases involving both trout and Daphnia, the cause of toxicity was traced to more than one compound or to excess concentrations of a specific compound resulting from a spill or biotreatment-related problems. [ABSTRACT FROM AUTHOR]