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TOXICITY OF SILVER NANOPARTICLES TO DAPHNIA MAGNA
Citation:
ALLEN, JOEL J., CHRISTOPHER IMPELLITTERI, D. A. MACKE, J. L. HECKMAN, C. T. NIETCH, J. M. LAZORCHAK, D. M. SHAW, AND L. H. SHAW. TOXICITY OF SILVER NANOPARTICLES TO DAPHNIA MAGNA. Presented at INTERNATIONAL SYMPOSIUM ON TOXICITY ASSESSMENT, TOYAMA, JAPAN, August 19 - 24, 2007.
Description:
Relatively little is known regarding toxicity of nanoparticles in the environment. It is widely assumed that the toxicity of nanoparticles will be less than that of their metallic ions. Also the effect of organics on metal toxicity is well established. Presented here are the results of Daphnia magna bioassays describing the toxicity of organically coated silver nanoparticles (<100nm) and the effect of organic additions. Experiments were performed using standard EPA test methodologies (48Hr static and 96Hr static-renewal) with and without the addition of organic material (algae, cerophyll, and algae+cerophyll). Silver nanoparticles were obtained from commercial sources. Stock suspensions were sonicated and filtered through 100nm filters. Stock suspension were digested via microwave digester (EPA Method 3015) and analyzed by inductively coupled argon plasma-optical emission spectroscopy (ICP) or graphite furnace-atomic absorption spectroscopy (GFAA). A stock suspension was diluted (with stirring) to create working suspensions and transferred to digestion vessels/organism exposure vessels. It is crucial to tightly control and repeat dilution and transfer techniques from experiment to experiment. A clear effect on LC50 concentration was observed: 11±5µg/L without food addition(48Hr), 40±8µg/L with food addition(96Hr). These values are similar to LC50 values found in the literature for ionic silver. These results suggest that toxicity of silver nanoparticles is in the same range as their metallic ions.