Assessing nanomaterial exposures in aquatic ecotoxicological testing: Framework and case studies based on dispersion...

Area of Science:

• Environmental Science
• Ecotoxicology
• Nanotechnology

Background:

• Engineered nanomaterials (ENMs) exhibit complex behaviors like settling and agglomeration in aquatic media.
• These behaviors challenge the reliability and interpretation of standard aquatic hazard bioassays designed for dissolved substances.

Purpose of the Study:

• To develop a testing framework for consistent aquatic hazard bioassays with ENMs.
• To establish methods for representative exposure metrology accounting for ENM behavior.
• To compare different exposure summary methods for toxicity endpoints.

Main Methods:

• A framework was designed and demonstrated with three case studies of ENMs with distinct characteristics.
• Pretests assessed particle concentration, agglomeration, and dissolution of ENMs in test media.
• Ceriodaphnia dubia bioassays compared nominal, arithmetic average, geometric average, and time-weighted average exposure methods.

Main Results:

• ENM behavior varied: silver nanoparticle powder was not dispersible, nano-TiO2 was dispersible but unstable, and coated AgNP was stable.
• Arithmetic means effectively expressed toxicity for stable ENMs.
• Time-weighted average concentrations were suitable for unstable nano-TiO2.

Conclusions:

• A consistent framework is crucial for reliable ENM ecotoxicity testing.
• The choice of exposure summary method depends on ENM stability and behavior in test media.
• This approach enhances the interpretation of aquatic hazard bioassays for nanomaterials.