Abstract
There is increasing concern about the toxicities and potential risks, both still poorly understood, of silver nanoparticles for the aquatic environment after their eventual release via wastewater discharges. In this study, the toxicities of sediment associated nano (<100 nm)-, micron (2–3.5 μm)- and ionic (AgNO 3)-Ag on the sediment-dwelling polychaete, Nereis diversicolor, were compared after 10 days of sediment exposure, using survival, DNA damage (comet assay) and bioaccumulation as endpoints. The nominal concentrations used in all exposure scenarios were 0, 1, 5, 10, 25, and 50 μg Ag/g dry weight (dw) sediment. Our results showed that Ag was able to cause DNA damage in Nereis coelomocytes, and that this effect was both concentration- and Ag form-related. There was significantly greater genotoxicity (higher tail moment and tail DNA intensities) at 25 and 50 μg/g dw in nano- and micron-Ag treatments and at 50 μg/g dw in the ionic-Ag treatment compared to the controls (0 μg/g dw). The nano-Ag treatment had the greatest genotoxic effect of the three tested Ag forms, and the ionic-Ag treatment was the least genotoxic. N. diversicolor did accumulate sediment-associated Ag from all three forms. Ag body burdens at the highest exposure concentration were 8.56 ± 6.63, 6.92 ± 5.86 and 9.86 ± 4.94 μg/g dw for worms in nano-, micron- and ionic-Ag treatments, respectively, but there was no significant difference in Ag bioaccumulation among the three treatments.
Highlights
Silver nanoparticles (Ag NPs) of size less than 100 nm are of concern due to their increasing use in consumer products which may pose risks for the environment and human health
Original particle size and shape of nano- and micron-Ag were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM)
Comet assay results demonstrated that all three Ag forms when added to sediment to which N. diversicolor were exposed can cause DNA damage and that, this effect is both Ag form- and concentration-related, with silver added as Ag NPs being most toxic and ionic-Ag being least toxic and indicating that DNA damage is a sensitive endpoint in N. diversicolor exposed to Ag
Summary
Silver nanoparticles (Ag NPs) of size less than 100 nm are of concern due to their increasing use in consumer products which may pose risks for the environment and human health. Applications using Ag NPs have become widespread in fields such as bio-sensing, the food industry, water purification, and medical sciences (Klaine et al, 2008). Ag NP-containing products, such as odor resistant textiles, food packaging, cosmetics, household appliances, and medical devices may release Ag particles (nanoparticles or aggregates) or Ag+ ions via wastewater discharge into the aquatic environment (Benn and Westerhoff, 2008). Aquatic organisms are likely to be exposed to these metal contaminants, and aggregation and precipitation of Ag NPs in aquatic systems suggest that benthic species may be especially at risk.
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