Metal-based nanomaterials in aquatic environments: What do we know so far about their ecotoxicity?

Area of Science:

• Environmental Science
• Ecotoxicology
• Materials Science

Background:

• Nanomaterials (NM) are increasingly produced and released into aquatic environments.
• Current knowledge on the ecotoxicological effects of environmental NM concentrations on aquatic biota is limited.
• Understanding NM environmental concentrations and their impact is crucial for risk assessment.

Purpose of the Study:

• To review the state of applied NM, their environmental concentrations, and predicted releases.
• To analyze literature for evidence of deleterious effects of environmental NM concentrations on aquatic organisms.
• To identify knowledge gaps regarding the harmfulness of current NM concentrations to aquatic biota.

Main Methods:

• Literature review of NM applications, environmental release, and ecotoxicity data.
• Analysis of reported NM concentrations in aquatic systems (ng to µg/L, mg/L for Ti-based NM).
• Synthesis of ecotoxicity data, focusing on effects on algae, invertebrates (Daphnia magna), and fish (Danio rerio).

Main Results:

• Si- and Ti-based NM are the most released, with predicted environmental concentrations ranging from ng to mg/L.
• Ecotoxicity data are scarce and unbalanced, primarily focusing on metal-based NM and specific species.
• Invertebrates, particularly microcrustaceans, appear most vulnerable, with some species experiencing mortality at environmentally relevant NM concentrations.
• Oxidative stress is a common response to NM exposure.
• Ti-based NM ecotoxicity is relatively well-studied in algae and fish, but data on other NM types and marine species are lacking.
• Carbon-based NM require further ecotoxicological investigation due to anticipated increases in release and application.

Conclusions:

• Environmental concentrations of some NM, particularly Ti-based, pose a concern for aquatic ecosystems.
• Invertebrates are highly vulnerable to NM exposure.
• Significant knowledge gaps exist regarding the ecotoxicity of various NM types (e.g., carbon-based) at environmentally relevant concentrations.
• Further research is needed to assess the risks of diverse NM to a wider range of aquatic organisms and environments.