Editorial note: The content of this article was previously provided as a press release of a journal article recently published in Environmental Toxicology and Chemistry. Throughout this year, SETAC Globe will provide various press releases to further highlight the interesting research that our SETAC journals are publishing.

In a newly published series appearing in Environmental Toxicology and Chemistry, researchers describe the current state of the science, the challenges and science-based best practices for modeling the influence of water chemistry on the toxicity of metals, which is a critical step in calculating protective metal concentrations in water for the protection of aquatic life.

Metals are abundant in the environment. In aquatic systems, they are managed by regulatory agencies by establishing numeric threshold concentrations considered acceptable to aquatic life, which can be referred to generically as protective values for aquatic life (PVALs). As early as the 1930s, researchers observed that the toxicity of metals to aquatic organisms varies with water chemistry. Since then, there have been a number of models designed to explain the toxicity of metals to aquatic organisms by describing and predicting the conditions that influence metals toxicity, and ultimately calculate PVALs. While the initial emphasis was placed on the influence of water hardness, subsequent findings contributed to a broader understanding of modifying factors that need to be considered in order to predict metal toxicity at a given location. Currently, bioavailability-based aquatic toxicity models that determine the influence of water chemistry on metal speciation and relate metal speciation to metal toxicity in mechanistically based approaches are available for several metals. The most robust of these mechanistic models are called Biotic Ligand Models. Simpler, empirical-based multiple linear regressions models have also been developed more recently.

SETAC TIP Metals in Freshwater cover

Read the latest SETAC Technical Issue Paper “Environmental Toxicity of Metals in Freshwater.”

Metals bioavailability-based aquatic toxicity models can be applied in two distinct areas in a regulatory context:

  1. To manage metals in the environments for the derivation of recommended PVALs
  2. To identify risk-based goals, which can be used to set discharge levels or cleanup goals

Chris Schlekat, guest editor on the series, notes that “the scientific community agrees that bioavailability-based aquatic toxicity models are recommended for use in environmental management.”

Unfortunately, the development of these models has outpaced their incorporation into regulation and application for some metals, which has left some water quality regulations outdated. Several challenges exist that could hamper the use of metals aquatic toxicity bioavailability-based models, such as:

  1. The divergence of model development approaches and the associated methods of validation
  2. The practicality of implementing models in regulatory programs
  3. The requirement of a variety of water chemistry parameters as input variables for some models

The series of articles summarizes the state of the science and goes on to detail considerations for model selection and model application, which will be useful for environmental professionals, managers and regulators. The models are at a state of maturity that supports their use to inform management decisions, and that will go a long way toward improving ecosystem protection.

Read the full series for free.

Read the Technical Issue Paper.

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