Tissue residue approach for chemical mixtures

Area of Science:

• Environmental Toxicology
• Risk Assessment
• Chemical Mixtures

Background:

• The tissue residue approach (TRA) offers advantages for assessing chemical mixture toxicity.
• Previous research established theoretical and experimental foundations for TRA in mixtures.
• Lack of mixture toxicity data in tissue or target-site concentrations has hindered development.

Purpose of the Study:

• To review literature on the TRA for chemical mixtures.
• To recommend a practical, tiered approach for regulatory and risk assessment applications.
• To integrate TRA with mixture toxicology for improved assessment.

Main Methods:

• A 3-tier framework integrating TRA and mixture toxicology.
• Tier I: Concentration Addition (CA) for mixture toxicity estimation.
• Tier II: Mixed model using CA and Independent Action.
• Tier III: TRA integrated with multisubstance potentially affected fraction (ms-PAF) for community protection.

Main Results:

• The proposed tiered approach provides a framework for mixture toxicity assessment.
• Modifications to bioaccumulation factor (BAF) calculations are needed for metals.
• Tier III derives protective tissue residue levels for aquatic communities (e.g., HC5).

Conclusions:

• The tiered TRA framework offers a practical solution for mixture toxicity assessment.
• This approach can be implemented in regulatory and risk assessment.
• It addresses limitations in current mixture toxicity data and assessment methods.