US EPA

This draft document presents a case study of engineered nanoscale silver (nano-Ag), focusing on the specific example of nano-Ag as possibly used in disinfectant sprays. This case study is organized around a comprehensive environmental assessment (CEA) framework, which combines a product life-cycle perspective with the risk assessment paradigm. The document does not draw conclusions about potential risks. Instead, it is intended to be used as part of a process to identify what is known and unknown about nano-Ag in a selected application and can be used as a starting point to identify and prioritize possible research directions to support future assessments of nanomaterials.

Engineered nanoscale materials (nanomaterials) 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. The draft document "Nanomaterial Case Study: Nanoscale Silver in Disinfectant Spray" is intended to be used as part of a process to identify what is known and, more importantly, what is not yet known that could be of value in assessing the broad implications of certain nanomaterials. The complex properties of various nanomaterials make evaluating them in the abstract or with generalizations difficult if not impossible. Thus, this document focuses on a specific example of nano-Ag in disinfectant spray products. After a number of individual case studies have been examined, refining a strategy for nanomaterials research to support long-term assessment efforts should be possible.

This case study does not represent a completed or even a preliminary assessment of nano-Ag; rather, it uses an assessment framework known as comprehensive environmental assessment (CEA), which starts with the product life cycle but encompasses fate and transport processes in various environmental media, exposure-dose characterization, and ecological and health effects, as well as other direct and indirect ramifications of both primary and secondary substances or stressors associated with a nanomaterial. The CEA approach is both a framework and a process; the latter aspect will be pursued through a collective judgment process that will be the subject of a future announcement.

Each chapter includes lists of questions that reflect information gaps in that portion of the document. Some of these knowledge gaps or research needs are specific to the use of nano-Ag in disinfectant spray; others may relate more broadly to nano-Ag irrespective of its application, while still others may apply more widely to nanomaterials in general. Readers are encouraged to consider the questions listed throughout the document and offer specific comments on how individual questions or research needs might be better expressed. If additional questions should be included or if information is already available to address some of the questions posed here, readers are also encouraged to provide such information. These and other comments should be submitted as explained below under Additional Information.

The information presented in the case study and the questions raised in this document are a foundation for a process to determine priorities among various research topics and directions. After that process has been completed, a final chapter will be added to this document to summarize highlights from preceding chapters and the major research issues that have emerged.

We will release the final report on the EPA Web site.

U.S. EPA. Nanomaterial Case Study: Nanoscale Silver in Disinfectant Spray (External Review Draft). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-10/081, 2010.

Comments on the assessment may be submitted and reviewed using the e-Government Regulations.gov Web site. From the site, select Environmental Protection Agency and the keyword EPA-HQ-ORD-2010-0658 (for the docket ID) to comment on this report.