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Objectives: This study was conducted to identify factors determining the toxicity of manufactured silver nanoparticles (AgNPs) on aquatic organisms.

Methods: For this purpose, we prepared several AgNPs with varied characteristics, including hydrodynamic size (nano-ABCAgCit vs-sized-ABCAgCit), impurities (ABCAg stock vs ABCAg), and citrate capping (ABCAgCit), using a commercially available manufactured AgNP (ABCAg stock). Acute tests were conducted using larval zebrafish (Danio rerioI). In addition, in order to determine the ecotoxicological potentials of various capping agents, toxicity tests were conducted with microbes, waterfleas, and fish for eight different capping agents that are used for NPs.

Results: The toxicity of AgNPs in terms of 96 h fish LC50 increased in the following order: ABCAg stock< ABCAg= ABCAgCit= nano-ABCAgCit< µ-sized-ABCAgCit< AgNO3. After removing impurities by dialysis, 96 h LC50 value decreased significantly from 126.6 µg/L (95% confidence intervals [CI]: 107.0-146.2)(ABCAg stock) to 78.6 µg/L (CI: 72.7-84.8)(ABCAg). For µ-sized-ABCAgCit (ranging between 3.9 and 40.6 nm) and ABCAgCit (40.6 nm and 9.1 µm), the 96 h LC50 of the former (43.9 µg/L, CI: 36.0-51.7) was approximately two-fold lower than that of the latter (87.0 µg/L, CI: 73.5-100.3).

Conclusions: In this study, we found that for acute lethality, the contribution of impurities and particle size was significant, but that of citrate was negligible.