Since the emergence of nanotechnology, researchers, regulators and the public have been concerned about the potential toxicity of nano-sized products. The fate and role of nanoparticles (NPs) in the environment are unclear as it is difficult to monitor the products that result from NP weathering. Silver NPs are of particular concern because of their rapidly growing use in antimicrobial applications and the known toxicity of the silver cation.

James Hutchison and co-workers, University of Oregon, USA, have found a way to directly observe changes in AgNPs over time. They tether the NPs to a functionalized transmission electron microscope grid. This allows the in situ weathering and the multitechnique characterization of identical particles over time. They find that all silver, both nano- and macro-scale, generates AgNPs when exposed to humid air or water. The NP size is not always static, especially when particles are on surfaces. Generation of NPs from manmade objects, e.g., wires, jewelry, and cutlery, suggests that humans have been exposed to these nanoparticles for a long time.

For these reasons, the team believes that environmental health and safety concerns should not be defined or regulated based upon size alone.

• Generation of Metal Nanoparticles from Silver and Copper Objects: Nanoparticle Dynamics on Surfaces and Potential Sources of Nanoparticles in the Environment
  R. D. Glover, J. M. Miller, J. E. Hutchison,
  ACS Nano 2011.
  DOI: 10.1021/nn2031319