Nanotechnology shows great promise in a variety of applications with attractive economic and societal benefits. However, societal issues associated with nanotechnology are still a concern to the general public. While numerous technological advancements in nanotechnology have been achieved over the past decade, research into the broader societal issues of nanotechnology is still in its early phases. Based on the data from the Web of Science database, we applied the main path analysis, cluster analysis and text mining tools to explore the (...) main research fronts and hierarchical structure of these societal issues. We found that the research studies fell into four categories: "General Toxicity and EHS (Environment, Health and Safety)," "Medicine and Cytotoxicity," "Assessment and Regulation," and "Environment and Ecotoxicity." These research studies have disclosed much information about the potential effect of nanotechnology on public health and the environment. Relatively speaking, the studies on the assessment, regulation, preventive solutions, and environmental protection are just emerging. This finding indicates that an abundance of effort should be conducted on these emerging themes to maximize the benefits of nanotechnology while minimizing its potential harm. The implications for various parties in this domain are also presented. (shrink)