A Unified Saltwater-Freshwater Biotic Ligand Model of Cu-Induced Olfactory Impairment to Salmonid Fishes

The effects of copper (Cu) on olfactory function in salmonid fishes has been receiving increased regulatory interest. In order to evaluate whether Cu criteria for fresh and salt water are protective against olfactory impairment, a biotic ligand model (BLM) is proposed for prediction of olfactory impairment caused by Cu to salmonid fishes in fresh and salt water. This model will be useful because only a limited number of Cu-olfactory studies have been conducted in fresh water and none have been conducted in salt water. The olfactory-parameterized BLM developed in the present study includes binding constants that are more appropriate for predicting olfactory responses than those used in the traditional branchial, acute-toxicity BLM and in a previously proposed olfactory-parameterized BLM. Based on Cu olfactory impairment thresholds using this modified BLM, the U.S. Environmental Protection Agency’s current BLM-based Cu criteria would protect against olfactory impairment in a variety of laboratory waters in which olfactory-impairment experiments have been conducted, in all but 1 of 133 stream sites in the western US, and in sea water.