New Approach to Evaluating Selenium Toxicity in the Environment

A new unified approach to evaluating the toxicity of selenium could help ecologists faced with varied and inconsistent approaches to assessing the toxicity of selenium in rivers, estuaries, and other water bodies. A team of U.S. Geological Survey (USGS) scientists proposed an ecosystem-scale model of the fate of selenium in the environment. The model quantifies how selenium is transferred from water and into predatory fish and birds through dietary uptake. The model integrates the chemistry of biological and geological systems and the physiological factors that control how various animals within food webs bioaccumulate selenium.

From Water To Predators: It's the Pathway That's Important

The approach shows that environmentally safe concentrations of selenium dissolved in water vary among ecosystems because the factors that affect whether selenium reaches toxic levels in fish and birds depends on the unique ecological and chemical conditions in each ecosystem. For example, the amount of selenium transferred within a local food web will differ depending on the species involved because different species bioaccumulate selenium at different rates and amounts. The unified approach is implemented in a computer model. The model provides a tool that ecologists, regulators, water resource managers, and other environmental professionals can use to:

• assess a site-specific ecological problem or occurrence of selenium exposure, and
• develop sound policies and guidelines regarding the ecological fate of selenium in the environment.

What Makes the Model Unique?

The model is unique because it integrates:

• the environmental chemistry of different forms of selenium (speciation),
• the transformation of dissolved selenium to particulate material,
• how much selenium enters the food web at its very base,
• the bioavailability of selenium,
• the bioaccumulation of selenium in aquatic invertebrates (animals without backbones), and
• the transfer of selenium from organism to organism (trophic transfer) within food webs all the way to predatory fish and birds.

References

Luoma, S.N., and Presser, T.S., 2009, Emerging opportunities in management of selenium contamination: Environmental Science & Technology, v. 43, no. 22, p. 8483-8487, doi:10.1021/es900828h.

More Information

• Selenium in the San Francisco Bay and Watershed
• Ecological Assessment of Selenium in the Aquatic Environment: A Pellston Workshop
• Linking Selenium Sources to Ecosystems, USGS and U.S. Fish and Wildlife Service
• Microbial Selenium Cycle in Nature
• Health and Environment - Selenium, USGS Energy Resources Program
• USGS Minerals Information: Selenium and Tellurium

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