Assessing the hazard and risk of metals to aquatic organisms poses many challenges. Previous studies have found that both total and dissolved concentrations of metals are not reliable indicators of their effects on ecosystems. The toxicity of metals can be modified by various physico-chemical water characteristics, such as dissolved organic carbon, pH, and hardness, by several orders of magnitude.

The use of bioavailability techniques, such as Lead Chronic BLM (Biotic Ligand Model), can help to overcome these difficulties. The BLM approach is currently recognized as the leading method for predicting metal bioavailability because it integrates existing knowledge about metal speciation in the solution surrounding the organism and the interactions between metal ions and competing ions at the binding sites on the organism-water interface, such as epithelial cells in fish gill tissue.

Lead Chronic BLM (Biotic Ligand Model)

The Lead Chronic Biotic BLM (Biotic Ligand Model) is a program designed for those interested in bioavailability-based evaluations of the chronic effects of lead in freshwater aquatic environments. It combines bioavailability models with detailed species sensitivity distribution (SSD) analyses to calculate the hazard concentration of lead for a specific water body.

The tool is a free online resource that was developed by ARCHE Consulting under contract for ILA, using biotic ligand models for lead toxicity developed by GhEnToxLab at Ghent University and chemical speciation codes from Visual Minteq at (KTH, Sweden). A comprehensive technical user guide provides information on the lead biotic ligand model and instructions for installing the tool.

Download it here!


User-friendly acute and chronic BLM tools

The Lead Chronic BLM tool requires input of several physico-chemical water characteristics that may not always be available. It is therefore considered more applicable to academic research. However, a user-friendly chronic BLM tool has recently been developed based and validated using the full academic version of the model. This tool, called Bio-met, is available to download here. An alternative tool that functions in a similar manner called PNEC-pro is also available and can be downloaded here. Other tools are also available that allow users to account for effect of water chemistry on the bioavailability (and toxicity) of lead. The lead environmental quality standard screening tool is a calculator that can be used to assess compliance with the European Environmental Quality Standard (EQS) for lead described in the EU Water Framework Directive. This tool, that can be downloaded here, only requires knowledge of water DOC levels. For those are interested in the acute BLM for lead, please download the tool from

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