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Studies conducted in Sweden in the early 1980s provided some of the first evidence that effluents from some pulp mills were capable of inducing toxic responses in fish at very low concentrations in the receiving environment. In response to these findings, studies were initated in Canada and impacts of primary treated bleached kraft mill effluent on reproductive function in fish were found. Reproductive impacts in fish were not limited to mills that used chlorine in the bleaching process and were also evident at some mills that employed secondary effluent treatment. In 1992, new federal regulations were passed under the Canadian Environmental Protection Act to control releases of dioxins and furans, and a new Pulp and Paper Effluent Regulation under the Fisheries Act set stricter limits for biological oxygen demand and total suspended solids. Very importantly, the new regulations included requirements for environmental effects monitoring (EEM) at all mill sites. This allowed the effectiveness of the control limits in protecting fish, fish habitat, and human use of fisheries resources to be assessed. At the same time, the Minister of the Environment launched an intensive government, industry, and university research program. Results from this research program along with feedback from the EEM program would then be used to define what additional control actions might be necessary. This article reviews the field studies and mechanistic research conducted in Canada following the implementation of the new federal regulations. Great progress has been made in this area, first demonstrating reproductive effects at various locations, then determining the mechanisms responsible for the reproductive effects at specific sites, followed by the demonstration of partial recovery in reproductive function following process and treatment changes in response to the new regulations. However, it is clear from the results of the first two cycles of the EEM program that mill effluents still affect the local receiving environments at a number of locations across Canada, and that continued research combining field studies, bioassay application, and chemical identification is required.

Laboratory tests have been used to assess the regulatory and research questions related to the effects of pulp mill effluents on aquatic biota. Acute, short-term laboratory tests have clearly shown the improvement in final effluent quality following installation of secondary treatment at Canadian pulp mills. In an effort to predict and investigate impacts on wild fish, laboratory bioassays were developed to examine sublethal endpoints: induction of hepatic mixed function oxygenase activity and reduction of sex steroid concentrations. These laboratory assays have been used to assess whole effluents, specific chemicals, and components of pulp mill processes, and to discriminate between historical and present-day effluent discharges. These tests have shown that induction of mixed-function oxygenase activity and reduction of sex steroid concentrations are produced by effluents from a variety of mill types, with and without chlorine bleaching, in hardwood and softwood pulping facilities, and before and after effluent treatment. These short-term bioassays have enabled reductions in sex steroid concentrations to be linked to mill process streams, and have provided information on effective waste stream treatment. Longer term, life-cycle fish bioassays have shown that chronic exposure to pulp mill effluents commonly results in growth enhancement, liver enlargement, and decreases in gonad size, secondary sex characteristics, and fecundity. These long-term laboratory exposures are able to mimic the most commonly observed alterations of wild fish exposed to pulp mill effluents: increases in condition factors, increases in liver-somatic indices, and decreases in gonadosomatic indices. This pattern of response is a combination of nutrient enrichment with metabolic disruption. The most sensitive and biologically meaningful endpoint is decreased reproduction in fish life-cycle exposures. As the laboratory tests move forward into the next decade, attention will focus on the reproductive endpoints and on the possibility of shortening the fish bioassays while still maintaining sensitivity and biological relevance.

This article is a review of research efforts over the last decade on the sources and characteristics of substances in Canadian pulp mill effluents associated with two responses in fish: (1) induction of detoxification enzymes and (2) reproductive effects. The initial uncertainty regarding the role of chlorine bleaching and dioxins in these responses was resolved by the mid 1990s, when it was determined that effects were not correlated with effluent adsorbable organic halogen (AOX) levels and that releases of dioxins had decreased substantially. In the mid 1990s researchers were able to partially attribute enzyme activity induction in fish to wood components, while other studies showed individual wood extractives had the potential to affect fish reproduction. A lack of correlation between threshold reproductive responses and effluent concentrations indicated additional unidentified compounds and mechanisms were involved. In the late 1990s, source identification approaches in concert with the development of mechanistically linked in vitro and in vivo bioassays showed multiple compounds are affecting production and signaling of sex steroids in fish. These substances are bioavailable and accumulated rapidly, consistent with the body of evidence that has shown a sustained exposure is required to produce both elevated enzyme activity and depressions in sex steroid levels. The patterns of these substances in effluents and fish tissues are not correlated with production type or effluent treatment. Collectively, these findings show that bioactive substances originate from wood and are derived from lignin and/or terpenoids, they are liberated during pulp digestion, and in kraft mills they are present in black liquor and chemical recovery condensates. Additional bioactive substances are also present in bleachery effluents containing residual lignin. The lack of a definitive identification of the responsible compounds has prevented an evaluation of the effectiveness of industry-wide process changes. Continued research into the identities, origins, and environmental fate of these substances and the efficacy of effluent treatment is required to determine their significance and relationship to the existing impacts of effluents from pulp and paper mills in Canadian aquatic ecosystems.

In Canada, Environmental Effects Monitoring (EEM) programs exist within two regulations: the Pulp and Paper Effluent Regulations and the new Metal Mining Effluent Regulations under the Canadian Fisheries Act. EEM provides a biological, effects-based feedback loop to assess the effectiveness of technology-based regulations in protecting receiving environments. The promulgation of the Pulp and Paper Effluent Regulations, in 1992, represented a significant step forward in the Canadian regulatory approach by incorporating directly into a regulation a requirement to assess the effects of effluent discharges on receiving environments using proven scientific monitoring methodologies. Similarly, an assessment of the aquatic impacts of mines resulted in recommendations to amend the Metal Mining Effluent Regulations, recently promulgated in 2002, and includes an EEM program as a science-based feedback loop. As such, these regulations recognize the possibility that national, technology-based standards may not necessarily protect all receiving environments because of the diversity and variability of both discharges and receiving sites across the country. Since that time, EEM has improved its flexibility by considering both advances in science and the uniqueness of monitoring sites across Canada to allow the most appropriate and cost-effective monitoring approaches at each site while maintaining national consistency. This paper discusses the use of monitoring under two Canadian regulations to assess effects on aquatic ecosystems. As well, the National EEM approach to maintaining up-to-date scientific practices in a national regulatory program is discussed using examples.

In 1997, we collected nine river sediment samples, including one duplicate, from above and below three pulp and paper mills on the Wisconsin River in Wisconsin, USA, and one mill on Beaver Dam Creek in Ontario, Canada. We also obtained twenty split sediment samples from the Wisconsin River that were collected by the US EPA in collaboration with Indiana University. Finally, we collected influent and effluent samples from eight pulp and paper related industries in the US and Canada. We analyzed all sediment and water samples for hexa- through decachlorobornanes. We did not detect any chlorobornanes in most of the sediments. When chlorobornanes were detected, the concentration in sediments below pulp mills were similar to or less than in those from above the same mills. Chlorobornanes could not be detected in any of the influent or effluent samples. Thus, pulp and paper mills and relate facilities are not a source of chlorobornanes.

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.

An XAD-2 resin concentrate of chlorination-stage pulp mill effluent was found to induce mutations in Salmonella typhimurium strains TA1535, TA100 and TA98 but not in strains TA1537 or TA1538. The presence of either S9 mix, S9 mix without cofactors, or heat-inactivated S9 mix, reduced the mutagenic effects. Dose-related increases in gene conversion, mitotic recombination and aberrant colony formation in Saccharomyces cerevisiae strain D7 also were found.