Nanosilver Toxic to Fish at "Surprisingly Low" Levels

Nanoparticles are used in an increasing number of products, from building materials to cosmetics; nanosilver in particular is widely used as an antibacterial coating in appliances and clothing. Because nanoparticles are so small—a nanometer is a billionth of a meter—they cannot be tracked by typical methods (see “Nanomaterials: How Big a Concern?”

EBN June 2012). Deborah Oughton, Ph.D., head of the project (which was commissioned by the Research Council of Norway), notes that researchers studying the effects of nanoparticles “often resort to the use of unrealistically high concentrations,” which can change the properties of the particles and reveal little about their behavior at commonly used levels. The new experiments were able to trace very low concentrations of nanoparticles by making them radioactive.

Earthworms and fish were exposed to radioactive silver, cobalt, and uranium nanoparticles, which were then tracked and found to accumulate in different parts of the body. “Surprisingly low” concentrations of nanosilver led to gill failure and death in salmon; aquatic species are a particular concern because nanosilver has been detected in wastewater from sewage treatment plants. Researchers also found that nanoparticles in soil break down through the slow release of potentially toxic ions over a long period of time.