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October 2, 2023
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Introductory Predicting the Toxicity of Metals to Aquatic Organisms: An Introduction to the Biotic Ligand Model
Hosted by U.S. EPA - Region 10


Water quality criteria (WQC) for metals have been developed to protect the integrity of aquatic systems. However, tests used to develop WQC were performed in laboratory waters that often are not representative of natural waters. Water effect ratio (WER) tests account for the effects of substances that alter the toxicity of metals in natural waters but can be costly and time consuming.

The biotic ligand model (BLM), a computationally efficient alternative to conducting WER tests, has been developed. The BLM may assist in developing technically defensible site-specific criteria, waste load allocations, and ecological risk assessments. It is intended to promote more focused and efficient uses of resources in the regulation and control of metals and the protection of the environment. The BLM is under review by regulatory agencies and is being considered for use in refining water quality criteria in the United States and elsewhere.

This course provides an introduction, background and rationale for the BLM, a description of its applications and case examples. The course will cover special considerations, data needs and data quality objectives, and model demonstrations. Demonstrations will be brief scenarios using hypothetical data sets and will cover model navigation, data input, and model outputs.

Course Objectives:

The attendee will learn about metal toxicity, factors that alter metal acute toxicity, metal water quality criteria development, sites and modes of action of metals, metal speciation, ligands, toxicity modeling and applications of the biotic ligand model.

For general information contact Diane Ruthruff by telephone at 206-553-5139 or via e-mail at

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Bullet  Seattle, WA
  February 25, 2009 - February 25, 2009
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