Rationale and Procedures for Using the Tissue-Residue Approach for Toxicity Assessment and Determination of Tissue, Water, and Sediment Quality Guidelines for Aquatic Organisms

This article describes a set of procedures for developing tissue, water, and sediment quality guidelines for the protection of aquatic life by using the tissue-residue approach (TRA) for toxicity assessment. The TRA, which includes aspects of the Critical Body Residue (CBR) approach, associates tissue concentrations of chemicals with adverse biological effects in a dose-response fashion that can be used to determine CBRs. These CBRs can then be used to develop tissue quality guidelines (TQGs), which may be translated into water or sediment guidelines with bioaccumulation factors. Not all toxicants are amenable to this type of analysis; however, some appear to exhibit relatively consistent results that can likely be applied in a regulatory framework. By examining tissue residues, variations in toxicokinetics (temporal aspects of accumulation, biotransformation, and internal distribution) are greatly reduced allowing a greater focus on toxicodynamics (action and potency) of the toxicants. The strongest feature of this approach is causality; hence, guidelines based on tissue concentrations are based on data demonstrating a causal relationship between the acquired dose and the biological effect. Because the TRA has utility for assessing the toxicity of contaminant mixtures, an approach is presented here using toxic unit values that can be used to assess the likelihood of observing toxic effects based on tissue residues.