Event Title

Bioavailability and Toxicity of Metal Mixtures Using the Tissue Residue Approach

Co-Author(s)

Moran, I.L.* ; Charlton, C.; Coverdale, A.M.; Kramarevsky, E.J.; Lawrence, E.J.; Sofield R.M.

Research Mentor(s)

Ruth Sofield

Description

Many toxicants are found in the environment as mixtures but because toxicants are routinely tested individually, mixture effects are poorly understood. Therefore, understanding the biological effects of realistic exposures, like mixtures, is essential to managing environmental contamination. In this study we explored how the presence of one metal affects the bioavailability and toxicity of a second metal when present in tandem. In addition to toxicity testing, we are measuring accumulated concentrations of metals in exposed seedlings. This data will be used within the tissue-residue approach (TRA) for toxicity assessment, which uses internal tissue concentrations as a dose metric rather than ambient aqueous concentrations. This approach removes exposure variability and allows for more accurate prediction of toxicity under realistic conditions. For this experiment we conducted acute toxicity tests with lettuce seedlings exposed to binary metal mixtures and used growth inhibition as the effect endpoint. The first step was to determine the tissue accumulation and toxicity of single metals (Al, Cu, Cd, Fe, Zn) to establish a baseline for bioavailability and toxicity. Next, we exposed seedlings to all combinations of binary mixtures and measured growth inhibition and bioaccumulation of metals. Using toxic units and the Isobole approach allowed us to classify the mixture effects as additive, synergistic or antagonistic, indicating whether the metals are more or less toxic when present together in a mixture. The toxicity results have shown antagonistic interactions for all mixtures tested, except Fe and Cu. The preliminary tissue concentration data suggests that the presence of certain metals can increase the uptake of another metal. Primarily applied to organic mixtures, experimental studies that utilize the TRA approach to describe metal mixture toxicity are rare. This work improves our understanding of mixture effects and bioavailability and is critical to predicting toxicity of metals in the environment under realistic conditions.

Document Type

Event

Start Date

May 2018

End Date

May 2018

Location

Environmental Sciences

Rights

Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.

Language

English

Format

application/pdf

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May 16th, 12:00 PM May 16th, 3:00 PM

Bioavailability and Toxicity of Metal Mixtures Using the Tissue Residue Approach

Environmental Sciences

Many toxicants are found in the environment as mixtures but because toxicants are routinely tested individually, mixture effects are poorly understood. Therefore, understanding the biological effects of realistic exposures, like mixtures, is essential to managing environmental contamination. In this study we explored how the presence of one metal affects the bioavailability and toxicity of a second metal when present in tandem. In addition to toxicity testing, we are measuring accumulated concentrations of metals in exposed seedlings. This data will be used within the tissue-residue approach (TRA) for toxicity assessment, which uses internal tissue concentrations as a dose metric rather than ambient aqueous concentrations. This approach removes exposure variability and allows for more accurate prediction of toxicity under realistic conditions. For this experiment we conducted acute toxicity tests with lettuce seedlings exposed to binary metal mixtures and used growth inhibition as the effect endpoint. The first step was to determine the tissue accumulation and toxicity of single metals (Al, Cu, Cd, Fe, Zn) to establish a baseline for bioavailability and toxicity. Next, we exposed seedlings to all combinations of binary mixtures and measured growth inhibition and bioaccumulation of metals. Using toxic units and the Isobole approach allowed us to classify the mixture effects as additive, synergistic or antagonistic, indicating whether the metals are more or less toxic when present together in a mixture. The toxicity results have shown antagonistic interactions for all mixtures tested, except Fe and Cu. The preliminary tissue concentration data suggests that the presence of certain metals can increase the uptake of another metal. Primarily applied to organic mixtures, experimental studies that utilize the TRA approach to describe metal mixture toxicity are rare. This work improves our understanding of mixture effects and bioavailability and is critical to predicting toxicity of metals in the environment under realistic conditions.