Effect-based trigger values for in vitro bioassays: Reading across from existing water quality guideline values

Area of Science:

• Environmental Science
• Toxicology
• Biotechnology

Background:

• Cell-based bioassays are increasingly used for water quality assessment, detecting effects even in clean water.
• Sensitive reporter-gene assays necessitate reliable trigger values to distinguish acceptable from unacceptable effect levels in monitoring.
• Existing methods often require complex in vitro to in vivo extrapolations, highlighting a need for a more direct approach.

Purpose of the Study:

• To propose a statistical method for deriving trigger values from chemical guideline values for cell-based bioassays.
• To introduce bioanalytical equivalents for integrating mixture effects of chemicals with similar modes of action.
• To establish effect-based trigger bioanalytical equivalent concentrations (EBT-BEQs) for receptor-mediated toxicity.

Main Methods:

• Developed a statistical approach to directly link chemical guideline values to bioassay trigger values.
• Proposed bioanalytical equivalents to account for concentration-additive effects of chemical mixtures.
• Utilized statistical distribution methods to derive EBT-BEQs for various bioassays.
• Applied the algorithm to 18 cell-based bioassays using 349 chemical guideline values.

Main Results:

• Derived 11 provisional effect-based trigger bioanalytical equivalents (EBT-BEQs).
• Demonstrated applicability using diverse water samples, showing most recycled water met proposed triggers.
• Identified that some wastewater effluent samples would not meet the derived triggers.
• Highlighted the method's adaptability to different water types and regulatory frameworks.

Conclusions:

• The proposed statistical method offers a direct way to derive bioassay trigger values from chemical guidelines, bypassing complex extrapolations.
• The concept of bioanalytical equivalents and EBT-BEQs provides a framework for assessing mixture toxicity in water quality monitoring.
• While provisional, the derived EBT-BEQs show promise for regulatory guidance, pending expansion of experimental data.