Differential Toxicity of Ionic Silver and Silver Nanoparticles: A Meta-Analysis of Ecotoxicological Studies

The literature on the toxicity of silver metal has increased in recent years. However, these studies differ in terms of silver forms, test organisms and exposure times. This makes it difficult to compare results and hinders the development of reliable guidelines on silver toxicity. This study presents a systematic meta-analysis to clarify the comparative toxicity of AgNO₃ and AgNPs on a wide range of biodiversity species, including prokaryotes, unicellular eukaryotes, invertebrates, fish, and terrestrial organisms. We screened 1117 studies published between 1945 and 2024, systematically applied the screening criteria and analyzed 28 data sets from 11 studies that met the eligibility and data quality criteria. The findings demonstrate that AgNO₃ exhibits higher toxicity than AgNPs in most cases, and this effect is particularly pronounced in various organisms. Furthermore, exposure duration is found to be a critical determinant, creating significant differences in both short-term (from 3 h) and long-term (96 h and above) exposures. This study demonstrates that silver toxicity is dependent on forms of silver, and shaped by exposure dose, time-dependent and organism types. A key point in this study is that the evidence base covers the years representing the broadest temporal scope among comparable studies. The results provide a quantitative synthesis of the existing literature, allowing for the identification of generalizable trends regarding the ecotoxicological effects of silver and shed light on the environmental risk assessment processes of silver forms.