From the Editors.

How can and should the risks from nanomaterials be managed? Effective governance of novel risks requires drawing together and using insights and methods from many parts of risk analysis and decision science, including risk assessment, risk communication, design of incentives and institutions, and coordination of many stakeholders and participants with diverse perceptions and concerns. In this issue, Stone et al. propose an ambitious framework for evidence-based, participatory risk governance of nanomaterials using risk assessment and other tools for risk-based decision-making; behavioral decision models for nanomaterial risks; and coordinated legal and regulatory requirements. The proposed framework emphasizes the needs and capabilities of different stakeholders in an effort to assure wide acceptance of resulting recommendations. Management policies for more familiar risks, as well as novel ones, also require review and empirical evaluation if we are to learn from experience how to manage risks most effectively. Bauer et al. consider empirical evidence on how effective restrictions on permissible flight operations for helicopter emergency medical services (HEMS) pilots aged 60 or older are in reducing the risks from heart attacks, strokes, or other cardiovascular events among pilots during flights. They find that a one-size-fits-all age-based policy has relatively little value: stable interindividual differences are large enough, and improvements in some risk markers among many pilots near age 60 are significant enough, so that individualized risk assessments for HEMS pilots near age 60 are likely to more effective than a uniform age-based policy.