Silver nanoparticle toxicity to Atlantic killifish (Fundulus heteroclitus) and zebrafish (Danio rerio) in complex environmental media: A comparison of laboratory, mesocosm, and microcosm studies
Monday, March 28, 2011
Nicholas School Doctoral Student
Division of Environmental Sciences and Policy
Abstract: The increasing use of silver nanoparticles (AgNPs) in consumer products and industrial applications has raised concern over their inevitable release into the aquatic environment. In this study, the effect of complex environmental media on AgNP toxicity was investigated in mesocosms using silver nitrate (AgNO3), and AgNPs coated with gum arabic (Ag-GA NP) and polyvinylpyrollidone (Ag-PVP NP). Water samples were taken from the mesocosms 24 h after dosing and compared to lab-incubated samples prepared by spiking control mesocosm water with Ag-GA NP, Ag-PVP NP and AgNO3, at the same concentrations observed in the mesocosms at 24 h. Samples were compared using acute toxicity testing on early life stage Atlantic killifish and zebrafish. Differences in toxicity between the lab-incubated water and the mesocosm samples were attributed to the more complex environment created by introducing plants, sediment, and variable environmental conditions (including natural light/UV). In general, lab-incubated samples were more toxic than samples taken from the mesocosms. However, for Ag-PVP NP, mesocosm samples were more toxic than lab-incubated samples, indicating that an environmental factor unique to the mesocosms caused increased toxicity of Ag-PVP NP. In addition, for mesocosm samples, both AgNPs were more toxic than AgNO3, on an equal mass basis. Therefore, the complex media is acting differently on Ag+ to reduce its toxicity in a manner that does not translate to AgNPs. A follow-up microcosm experiment was used to investigate the role of different sources of dissolved organic material (DOM) on AgNP toxicity. Microcosm experiments using the same particles with four different environmental scenarios indicate that plants were the strongest protective factor and that sediment may have contributed to the increased toxicity of Ag-PVP NP. These results suggest that conventional laboratory testing and equation of AgNPs to Ag+ on a mass basis may be inadequate for risk assessment.