Effects assessment: boron compounds in the aquatic environment.

Area of Science:

• Environmental Toxicology
• Aquatic Ecotoxicology
• Chemical Risk Assessment

Background:

• Boron compounds were previously considered low toxicity to aquatic environments, with predicted no effect concentration (PNEC) around 1 mg B/L.
• Existing toxicity data for boron is comprehensive, but lacks chronic data for aquatic insects and plants.

Purpose of the Study:

• To re-evaluate the toxicity of boron compounds in the aquatic environment using updated data and methods.
• To determine more accurate PNEC values for boron using standard assessment factor and species sensitivity distribution (SSD) approaches.

Main Methods:

• Evaluation of existing aquatic toxicity data for boron compounds.
• Application of the standard assessment factor approach.
• Application of the species sensitivity distribution (SSD) approach to derive Hazardous Concentration 5% (HC5).

Main Results:

• The standard assessment factor approach yielded a PNEC of 0.18 mg B/L (1.03 mg boric acid/L).
• The SSD approach resulted in a PNEC of 0.34 mg B/L (1.94 mg boric acid/L).
• These values are close to natural boron background concentrations in some European regions.

Conclusions:

• Boron compounds may pose a hazard to aquatic organisms at concentrations near natural background levels.
• Some aquatic ecosystems may be highly sensitive to anthropogenic boron inputs.
• Anthropogenic boron may cause toxic effects in organisms adapted to low boron concentrations.