Nanomaterial Case Studies: Nanoscale Titanium Dioxide (External Review Draft)

Engineered nanoscale materials (nanomaterials) have been described in part as having at least one dimension on the order of approximately 1 to 100 nanometers (nm) and unique or novel properties that arise from their small size. This draft document is a starting point to determine what is known and what needs to be known about selected nanomaterials as part of a process to identify and prioritize research to inform future assessments of the potential ecological and health implications of these materials. Two specific applications of nanoscale titanium dioxide (nano-TiO₂) are considered: as an agent for removing arsenic from drinking water and as an active ingredient in topical sunscreen. These case studies do not represent completed or even preliminary assessments, nor are they intended to serve as a basis for risk management decisions in the near term on these specific uses of nano-TiO₂. Instead, the intent is to use this document in developing the scientific and technical information needed for future assessment efforts.

The case studies are organized around the comprehensive environmental assessment (CEA) approach, which combines a product life-cycle framework with the risk assessment paradigm. Risk assessment relates exposure and effects information for a substance or stressor; CEA expands on this paradigm by including life-cycle stages and considering both direct and indirect ramifications of the substance or stressor. Each chapter includes a list of questions that reflect information gaps in that portion of the document. Some of these information gaps or research needs are specific to the respective uses of nano-TiO₂ either as a water treatment agent or as an ingredient in topical sunscreen. Other research needs may apply more broadly to nano-TiO₂ irrespective of its application, and still other needs may apply even 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 comments as well. These and other comments should be submitted as explained below under Additional Information.