Societal impact is an increasingly important imperative of academic funding. However, there is little research to date documenting how impact is accomplished in practice. Drawing on insights from Actor-Network Theory, we explore the research-policy interface within an interdisciplinary research project on the relationships between air pollution and human health. Health policy impact was important to the researchers for moral as well as pragmatic reasons but it was a goal that was seen as potentially in tension with that of doing science. In fields such as air pollution and health, networks of policymakers and researchers are inevitably entangled, and we found that processes of engagement operated to delineate science from policy. Health was initially black-boxed and under-explicated, used as a signifier in itself for societal impact. By mobilising networks of policy actors, brought together in workshops to rank the importance of policy scenarios for the research team, the connections between air pollution and health were materialised and made actionable. This was achieved by framing existing data sets, emission technologies, policy expertise, pollutant species and human health in particular ways and, in doing so, excluding others. The process of linking air pollution and health research to achieve societal impact not only influenced how these phenomena were known but, critically, enabled and constrained potential policy responses. Tracing these research arrangements made the material discursive processes of 'impact' visible and analysable as objects of social science scholarship, and therefore generated a productive site for critically engaging with processes of environment and health science and policy.