A decade of research on the environmental impacts of pulp and paper mill effluents in Canada: field studies and mechanistic research.

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.