1. Characterization of Nanomaterials: Accurately characterizing the physical and chemical properties of nanomaterials is challenging but essential for understanding their behavior.
2. Dose Metrics: Traditional dose metrics like mass concentration may not be appropriate for nanomaterials. Alternative metrics, such as surface area or particle number, are often required.
3. Long-term Studies: The long-term effects of nanomaterials are not well understood, and long-duration studies are needed to assess chronic toxicity and potential carcinogenicity.
4. Standardization: There is a need for standardized methods and protocols for safety testing to ensure consistency and comparability of results.
