The Temporal Response Surface: A Novel Method for the Assessment of Delayed and Time-Cumulative Aquatic Ecosystem...

Area of Science:

• Environmental Toxicology
• Ecotoxicology
• Risk Assessment

Background:

• Current Australian pesticide risk assessments use species sensitivity distributions (SSDs) for chronic exposure guidelines.
• Existing guidelines do not adequately address cumulative toxicity from extended pesticide exposure, like neonicotinoids.
• There's a lack of suitable alternatives to default acute to chronic ratios (ACRs) for assessing such chemicals.

Purpose of the Study:

• Introduce the Temporal Response Surface (TRS) method to incorporate exposure duration into SSDs.
• Develop a novel approach for setting meaningful aquatic ecosystem protection guidelines.
• Address the gap in risk assessment for chemicals with cumulative toxicity.

Main Methods:

• Developed the Temporal Response Surface (TRS) method using taxa-specific regression relationships.
• Integrated exposure duration directly into species sensitivity distributions (SSDs).
• Applied the TRS method to imidacloprid to determine protective concentrations (PCs) over time.

Main Results:

• TRS method shows protective concentrations (PC99, PC95, PC90, PC80) decrease rapidly within 30 days of exposure.
• Protective concentrations continue to decline with longer exposure periods.
• Previous risk assessments may have underestimated imidacloprid's chronic toxicity.

Conclusions:

• The TRS method provides a holistic approach for assessing chemicals with delayed or cumulative toxicity.
• This method addresses policy and risk assessment gaps for enhanced aquatic ecosystem protection.
• TRS enhances the protection of Australian and international aquatic ecosystems.