The hazard assessment of pulp and paper effluents in the aquatic environment: A review

The hazard assessment of pulp and paper effluents in the aquatic environment is a complex task. Hundreds of individual compounds in pulping effluents and site-specific differences in processes, effluent treatment, and receiving ecosystems hinder hazard assessment. As a result, it is difficult to relate environmental effects with specific contaminants. Conventional parameters such as organic and nutrient loadings, solids deposition, and color complicate efforts to define chemical toxicants by causing environmental impacts at community and population levels. Reproduction is the most sensitive, consistent, and relevant end point tested to date in the laboratory, in mesocosms and experimental streams, and in field situations near some pulping discharges. Despite the application of a wide range of within-organism measurements, only the induction of mixed-function oxidase activities has been associated with exposure to particular effluent compounds in field situations. No complete mechanism of toxic action has been demonstrated that connects contaminant exposure, within-organism responses, whole-organism effects, and effects at the population and the community levels. Hazard assessments of pulping effluents require multidisciplinary efforts that integrate chemical, toxicological, and biological data at several organizational levels. Tiered or stepwise assessments are recommended that first clarify what adverse effects have occurred and then attempt to identify the responsible contaminants.