Assessment of a New Approach Method for Grouped Chemical Hazard Estimation: The Toxicity-Normalized Species...

Area of Science:

• Environmental toxicology
• Ecotoxicology
• Chemical risk assessment

Background:

• Reducing animal testing is a key challenge in chemical risk assessment.
• Assessing risks to diverse aquatic species for numerous chemicals with limited toxicity data is difficult.
• Novel methods are needed to develop compound-specific hazard concentrations.

Purpose of the Study:

• To introduce and evaluate the toxicity-normalized species sensitivity distribution (SSDn) approach.
• To develop compound-specific hazard concentrations using data from toxicologically similar chemicals.
• To compare the SSDn approach with the single-chemical SSD method.

Main Methods:

• Developed an SSDn using acute toxicity values from multiple related chemicals, normalized by a common species' sensitivity.
• Computed a toxicity-normalized hazard concentration (HC5n) from the SSDn's fifth percentile.
• Determined chemical-specific HC5 values by back-calculating HC5n using chemical-specific normalization species sensitivity.
• Compared HC5 values generated by SSDn and single-chemical SSD methods using data for nine transition metals.

Main Results:

• The SSDn approach yielded accurate HC5 values when guiding principles were applied.
• Comparisons with single-metal SSDs confirmed the accuracy of the SSDn method.
• Identified guiding principles for the effective application of the SSDn approach.

Conclusions:

• The SSDn approach is a promising method for developing statistically robust hazard concentrations.
• This method is particularly valuable when adequate taxonomic representation is unavailable for a single chemical.
• The SSDn approach aids in reducing animal testing and assessing risks to aquatic environments.