John Wiley & Sons, Ltd.

Silver nanoparticle toxicity to Daphnia magna is a function of dissolved silver concentration

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The most persistent question regarding the toxicity of silver nanoparticles (AgNPs) is whether this toxicity is due to the nanoparticles themselves or the silver ions (Ag+) they release. The present study investigates the role of surface coating and the presence of dissolved organic carbon on the toxicity of AgNPs to Daphnia magna and tests the hypothesis that the acute toxicity of AgNPs is a function of dissolved Ag produced by nanoparticle dissolution. Toxicity of silver nitrate (AgNO3) and AgNPs with surface coatings: gum arabic (AgGA), polyethylene glycol (AgPEG), and polyvinylpyrrolidone (AgPVP) at 48 hours was assessed in US Environmental Protection Agency moderately hard reconstituted water alone (US EPA MHW) and augmented with Suwannee River dissolved organic carbon (SRDOC). As expected, AgNO3 was found most toxic to D. magna, and AgPVP the least toxic. In general, SRDOC presence reduced the toxicity of AgNO3, AgGA and AgPEG while the toxicity of AgPVP was unaffected. The measured dissolved silver concentrations (measured dissolved Ag) for all the AgNPs and AgNO3 at the 48‐hour median lethal concentration (48h LC50) in MHW were similar. The presence of SRDOC decreased the ratio of measured dissolved Ag to measured total silver concentration (measured total Ag). These results supported the hypothesis that toxicity of AgNPs to D. magna is a function of dissolved Ag concentration from these particles. Environ Toxicol Chem © 2013 SETAC

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