the information needed to implement risk-management strategies aimed at reducing the potential for harm to human health and the environment. That feedback also informs the design, manufacture, and use of future ENMs.

The conceptual framework, described later in this chapter, reflects a coordinated, strategic research effort that is characterized by three key features:

•  A reliance on principles that help to identify emergent, plausible, and severe risks resulting from designing and engineering materials at the nanoscale, rather than an adherence to rigid definitions of ENMs.

•  A value-chain and life-cycle perspective that considers the potential harm originating in the production and use of nanomaterials, nanomaterial-containing products, and the wastes generated.

•  A focus on determining how nanomaterial properties affect key biologic processes that are relevant to predicting both hazard and exposure; for example, nanomaterial-macromolecular interactions that govern processes ranging from protein folding (a basis for toxicity) to the adsorption of humic substances (that may influence mobility or bioavailability of the materials).

Environmental and human health risk assessment of nanomaterials is severely limited by lack of information on exposure to these materials (for example, information on fate, transport, and transformations) and on the hazards that they present. In contrast with previous research strategies that took a sequential approach to evaluating exposure and hazard for assessing nanomaterial-related risks, the committee’s framework considers evaluations of hazards and exposure as processes that occur in tandem, and it accounts for the wide variety of matrices and transformations of nanomaterials along the value chain and across the life cycle (discussed in more detail later in this chapter).

The framework is to be implemented through a research agenda that begins with understanding how nanomaterial properties may affect fundamental processes—processes that are common in determining both exposures and hazards. By focusing on these processes, the goal of advancing exposure and hazard assessment under conditions of uncertainty can be addressed in a predictive and generalizable fashion that helps to inform decision-making on current and future nanomaterials. Knowledge of these processes has immediate applicability in comparing risks among materials and providing criteria for establishing priorities for research on nanomaterials that are on the market, for providing feedback on research needs and priorities, and for providing evidence needed to reduce the risks posed by nanomaterials that are on the market or are under development.

The sections below address the utility of risk assessment in framing a research strategy for the EHS aspects of nanomaterials, the conceptual framework that is informed by risk assessment, and the principles for setting priorities among research needs on the basis of the properties of nanomaterials.



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