National Assessment of Pulp and Paper Environmental Effects Monitoring Data: Findings from Cycles 1 through 3

Under the Fisheries Act, the Regulations Amending the Pulp and Paper Effluent Regulations require Canadian pulp and paper mills to conduct Environmental Effects Monitoring (EEM) to assess effects potentially caused by their effluent. These studies generally include some or all of the following key components: a fish population field survey to assess effects on fish, a benthic invertebrate community field survey to assess effects on fish habitat, and studies to assess effects on the usability of fisheries resources, including a study of dioxins and furans in fish tissue and a tainting study. In addition, sublethal toxicity testing is conducted to aid in assessing effluent quality.

The EEM program is structured into “cycles,” whereby a mill conducts an EEM study every three to six years. The purpose of this report is to present and discuss the results of the national assessment of EEM data collected from the receiving environments of pulp and paper mills across Canada for Cycle 3, which was conducted from April 1, 2000 to April 1, 2004. In addition, these findings are compared to those from earlier cycles.

Two complementary quantitative approaches were used to provide an assessment of the overall effects of pulp and paper mill effluents on aquatic biota: 1) tabulation of the results of individual mill comparisons and 2) meta-analyses to investigate national patterns of effects. The response patterns observed for effluent-exposed fish and benthic invertebrates during Cycle 3 were, for the most part, quite similar to those observed during Cycle 2.

The national average response pattern measured for fish in both Cycles 2 and 3 was one typically associated with nutrient enrichment overlaid by metabolic disruption. That is, exposed fish have consistently shown evidence of increased food availability or increased food absorption (fatter, faster growing, with larger livers) together with disruption of allocation of resources to reproduction (smaller gonads), in comparison to reference area fish. Further, at a national level, the reduction in fish gonad size has remained virtually unchanged over two cycles of data collection. This metabolic disruption may include some aspect of endocrine disruption associated with problems in producing sufficient sex steroid hormones. Other observed response patterns for fish have included nutrient enrichment without measurable metabolic disruption, nutrient limitation, and chemical toxicity. Tainting was confirmed at one mill and dioxins and furans exceeded fish tissue guideline levels at three mills.

The national average response for benthic invertebrate communities in both Cycles 2 and 3 was indicative of eutrophication, ranging from mild to more pronounced, partly depending on habitat type. More specifically, benthic invertebrate communities exposed to pulp mill effluent have commonly exhibited increases in abundance, together with some combination of increases, decreases or no change in taxon richness, depending on the degree of eutrophication. Other observed benthic invertebrate response patterns have included toxicity or smothering effects.

The sublethal toxicity data showed clear improvements in effluent quality from Cycle 1 to Cycle 2, with, for the most part, no further changes in effluent quality in Cycle 3. It should be noted, however, that the sublethal toxicity reporting methodology and selection of tests do not track all aspects of effluent quality (and some tests showed low sensitivity to effluent exposure). In particular, they do not currently measure nutrient enrichment effects of the effluent, which was the most commonly observed kind of effect measured in the fish and benthic invertebrate field surveys, although the tests could be modified to provide some information on nutrient enrichment effects. Also of note, and consistent with the reductions in gonad size measured in the fish field survey, the most sensitive sublethal toxicity tests were those that measured a reproductive endpoint (although these did not include fish tests).

Although the fish and benthic invertebrate responses measured in the field surveys were highly consistent between Cycles 2 and 3 at a national level, some possible shifts in patterns of effects were also observed. The Cycle 3 fish data showed an overall lessening of the increased growth and condition observed in Cycle 2. On a habitat-specific basis, the benthic invertebrate data showed evidence of a possible lessening of toxicity/smothering effects in marine habitats, as well as more pronounced eutrophication in freshwater depositional habitats. The causes of these possible shifts are unknown at present, and it is possible that they are related to other factors such as background temporal variability in the receiving environment or changes in study designs between cycles. The results obtained in Cycle 4 and beyond, together with more focused studies at some mills, will help to answer these questions.

Because not all statistically significant effects are necessarily considered serious, Environment Canada has developed critical effect sizes (CES) for the fish and benthic invertebrate endpoints. These CES are used to help identify those differences that could be important and where more information (e.g., extent and magnitude of effects) is desirable in order to better understand the ecological significance of these differences. The use of these CES, together with the magnitudes and statistical significance of effects measured during Cycles 2 and 3, has identified a subset of mills where monitoring efforts can be reduced or where more extensive monitoring should be conducted. Finer-resolution evaluations will be made at the regional level, but initial estimates are that approximately 20% of the monitored mills are expected to conduct only sublethal toxicity testing in Cycle 4, while roughly another 20% are expected to progress to determinations of the extent and magnitude of effects or, for some mills, investigations of the causes of the effects.

Previous to the EEM program, a broad view of pulp and paper mill effluent effects on aquatic biota was not available at a national level in Canada (or, at this geographic scale, in other jurisdictions). The extensive database generated by the EEM program, and the subsequent analyses, have provided a fairly robust picture of the effects of these effluents on receiving waters across the country.