Impact of Humic Acid on the Persistence, Biological Fate and Toxicity of Silver Nanoparticles: A Study in Adult Zebrafish

Abstract In recent years silver nanoparticles (AgNPs) have found their way into the consumer market as part of textiles, coating and devices. The disposal of products containing AgNPs can lead to NP accumulation in aquatic environments and to the formation of sediments by adsorption with humic acid (HA). Toxicological end points of AgNPs in the presence of HA were assessed in adult zebrafish. Zebrafish (n = 7/group) were exposed for 96 h to 0, 10, 20, 30, 40 and 60 mg/L AgNPs with or without 20 mg/L HA. The toxicity of AgNPs+HA was lower (LC50 = 40.56 mg/L) than for AgNPs (LC50 = 25.0 mg/L). AgNPs+HA did not induce significant changes on DNA fragmentation and organ histology. The amount of silver per organ were mesured by μPIXE and ICP-MS. TEM and DLS analysis showed that though there is complexation between HA and AgNPs, μPIXE shows that the biological fate of AgNPs was not altered by HA. However, silver concentration was higher in fish exposed to AgNPs than to AgNPs+HA. These results show that HA influence the behavior, bioavailability, and toxicity of AgNPs in zebrafish reducing silver uptake and fish mortality.