Societal evaluation of new technologies, specifically nanotechnology and genetically engineered organisms (GEOs), challenges current practices of governance and science. When a governing body is confronted by a technology whose use has potential environmental risks, some form of risk analysis is typically conducted to help decision makers consider the range of possible benefits and harms posed by the technology. Environmental risk assessment (ERA) is a critical component in the governance of nanotechnology and genetically engineered organisms because the uncertainties and complexities surrounding these technologies pose such risk potential. However, GEOs are unique technologies, and there is widespread, international recognition (e.g., the Cartagena Protocol on Biosafety of Living Modified Organisms) that many traditional forms of ERA are not well-suited for evaluating them. Nanotechnology products are also likely to need different models of risk assessment, as there is very little information on their fate, transport, and impacts in the environment.