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Building on breakthroughs recently made at kraft mills, a survey of mechanical pulp and paper mill effluents was undertaken to gain insights concerning potential effects on fish reproduction. Effluents from seven Canadian mills were characterized chemically for conventional parameters such as biochemical oxygen demand (BOD) and total suspended solids (TSS). Each sample was further subjected to solvent extraction followed by gas chromatographic separation for the determination of resin/fatty acids and for the estimation of a gas chromatography (GC) profile index. Each mill effluent was assessed for the potential to affect fish reproduction in the laboratory using a five day adult fathead minnow (Pimephales promelas) egg production bioassay with exposures to 100% effluent. The seven effluents were found to have substantial variation both in terms of chemical characterization and effects on fish reproduction. Temporal variations were also noted in effluent quality at mills sampled on different occasions. Similar to what has been observed for kraft mills, a general trend of greater reductions in egg production caused by effluents with greater BOD concentrations and GC profile indices was noted. Effluents with BOD > 25 mg/L and GC Profile indices >5.0 caused a complete cessation of egg production. At the same time, about half of the total effluents sampled had BOD < 25 mg/L and GC profile indices <5.0 and caused no significant effects on egg production, suggesting these values may be useful as effluent quality targets for mechanical pulp and paper mills. However, 3 out of 14 effluents sampled had BOD < 25 mg/L and GC profile indices <5.0 and caused significant reductions in egg production. The reason(s) for reproductive effects caused by such effluents is presently unclear. The effluent quality parameters considered in this study may require further refinement to address their utility in predicting the adverse reproductive effects induced by effluents from mechanical pulp and paper mills.

This study investigates factors affecting reproduction in fish exposed to pulp and paper mill effluents by comparing effluents from countries with varying levels of documented effects. To explore the hypothesis of wood as a common source of endocrine disrupting compounds, feedstocks from each country were analyzed. Analyses included in vitro assays for androgenic activity (binding to goldfish testis androgen receptors), estrogenic activity (yeast estrogen screen), and neurotransmitter enzyme inhibition (monoamine oxidase and glutamic acid decarboxylase). Chemical analyses included conventional extractives, known androgens, and gas chromatograph index (GCI) profiles. All effluents and wood contained androgenic activity, particularly in nonpolar fractions, although known androgens were undetected. Effluents with low suspended solids, having undergone conventional biotreatment had lower androgenic activities. Estrogenic activity was only associated with Brazilian effluents and undetected in wood. All effluents and wood inhibited neurotransmitter enzymes, predominantly in polar fractions. Kraft elemental chlorine free mills were associated with the greatest neurotransmitter inhibition. Effluent and wood GCI profiles were correlated with androgenic activity and neurotransmitter enzyme inhibition. Differences in feedstock bioactivities were not reflected in effluents, implying mill factors mitigate bioactive wood components. No differences in bioactivities could be discerned on the basis of country of origin, thus we predict effluents in regions lacking monitoring would affect fish reproduction and therefore recommend implementing such programs.

A long-term monitoring study was conducted on effluents from a bleached kraft pulp and paper mill located in Eastern Canada. The study was designed to gain insights into temporal effluent variability with respect to fish reproduction as it related to production upsets, mill restarts and conditions affecting biological treatment performance. Final effluent quality was monitored between February 2007 and May 2009 using biochemical and chemical oxygen demand, total suspended solids, resin and fatty acids, a gas chromatographic profiling index, and the presence of methyl substituted 2-cyclopentenones. Selected effluent samples were evaluated for effects on fish reproduction (egg production) using a shortened version of the adult fathead minnow reproductive test. The events relating to negative effects on fish reproduction were upsets of the pulping liquor recovery system resulting in black liquor losses, operational upsets of the hardwood line resulting in the loss of oxygen delignification filtrates, and conditions that reduced the performance of biological treatment (e.g., mill shutdown and low ambient temperatures). The reductions in egg production observed in fathead minnow were associated with biochemical oxygen demand values > 20 mg/L, GC profiling indices > 1.2 and the presence of methyl-substituted 2-cyclopentenones at concentrations > 100 μg/L. This study demonstrated the importance of both in-plant measures for controlling the loss of organics as well as the optimum operation of biological effluent treatment for eliminating effluent-related effects on fish reproduction (egg production) in the laboratory.

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.

The results and interpretations of published Canadian field studies on the reproductive status of fish in waters receiving pulp and paper mill effluent discharges were reviewed. Most of the information was obtained from indicator measurements such as gonad size, fecundity, and serum steroid levels in wild fish sampled at reference and effluent-exposed sites. Difficulties in selecting appropriate sampling sites, natural variability, and the ecological relevance of the indicator measurements were identified as major complicating factors for the interpretation of the field data. Consequently, it was not possible to conclude to what extent, if any, widespread effects on fish reproduction are being caused by pulp and paper mill effluents or that specific manufacturing processes are causing such effects. Further research on the normal variability and predictive capability of reproductive indicators, for example, using an integrated approach (i.e., laboratory testing, mesocosm studies, and field work), is recommended.