According to a Federal Register notice published on Friday, August 13th, EPA is announcing the release of a draft document entitled “Nanomaterial Case Study: Nanoscale Silver in Disinfectant Spray" and opening it up for a 45-day public comment period (which ends September 27, 2010). The draft was issued by the National Center for Environmental Assessment within EPA's Office of Research and Develpment, and is "intended to serve as part of a process to help identify and prioritize scientific and technical information that could be used in conducting comprehensive environmental assessments of selected nanomaterials." At this point the document doesn't draw any safety conclusions regarding nanoscale silver, just what is known and unknown so that they can make decisions on what to require for future assessments.
The document can be found on the NCEA web site.
From the site, "engineered nanoscale materials...have been described as having at least one dimension between 1 and 100 nanometers (nm). They often have novel or unique properties that can arise from their small size. Like all technological developments, nanomaterials offer the potential for both benefits and risks. The assessment of such risks and benefits requires information, but given the nascent state of nanotechnology, much remains to be learned about the characteristics and effects of nanomaterials."