Toxicity and uptake of nanosilver by Pseudokirchneriella subcapitata and Daphnia magna

In recent years, there has been an explosive increase in applications from dishwashers to dietary supplements using silver nanoparticles because of their reported antibacterial properties. As a result, it is inevitable that environmental releases will become significant in the near future. Recent studies have suggested that the extensive database of toxic effects for Ag. may be of limited use for a risk assessment of nanosilver effects in aquatic organisms. My objectives were to determine the toxicity of nanosilver in comparison with ionic silver and to determine uptake of nanosilver by the unicellular algae Pseudokirchneriella subcapitata. To determine the LC 50 for Daphnia magna, 24hr old neonates were exposed to various concentrations of ionic and nanosilver without food for 96 hours. To determine the uptake of nanosilver by algae, algae were exposed to nanosilver for 8 days. The LC50 for Daphnia magna was 10 mug/L (95% confidence interval, 95% CI: 9.2 - 11) for nanosilver and 1.3 mug/L (95% CI: 1.0 - 1.6) for ionic silver. The IC50 for algae was 500 mug/L (95% CI: 300 - 650) for nanosilver and 26 mug/L (95% CI: 15 - 47) for ionic silver. TEM images depicted that 10% of the algae exposed had nanosilver in their protoplasm and suggest that nanosilver could be a potential hazard to the environment through direct toxicity and biomagnification through the food chain. Further research is required in areas of particle characterization, particle behavior and bioavailability of nanosilver in the environment.