Estimating population-level HC5 for copper using a species sensitivity distribution approach.

Area of Science:

• Environmental toxicology
• Ecological risk assessment
• Aquatic ecotoxicology

Background:

• Accurate benchmark concentrations are crucial for ecological risk assessments of aquatic organisms.
• Species sensitivity distribution (SSD) is a key method for deriving these benchmarks.
• Understanding population-level effects of chemicals like copper is vital.

Purpose of the Study:

• To derive the population-level hazardous concentration for 5% of species (PHC5) for copper using an SSD approach.
• To assess the effectiveness of the population-level SSD approach in protecting aquatic species richness.
• To compare population-level benchmarks with individual-level benchmarks.

Main Methods:

• Utilized available copper toxicity data and population models.
• Estimated population threshold concentrations for 13 freshwater species (algae, invertebrates, fish).
• Fitted a log-normal distribution to population threshold concentrations to estimate PHC5.

Main Results:

• The estimated PHC5 for copper was 6.8 µg/L (95% CI, 1.8–13.6 µg/L).
• The population-level SSD estimate closely aligned with a field-derived threshold concentration.
• The population-level PHC5 was comparable to the individual-level HC5 from EU risk assessments.

Conclusions:

• The population-level SSD approach appears effective for protecting species richness in natural environments.
• The margin between individual-level and population-level SSD benchmarks can be narrow.
• Further attention is needed to ensure population-level protection when using individual-level SSD approaches.