Environmental risks are contested topics, and definitions of risk often vary across contexts, disciplines, and institutions. Identifying and describing differences between risk definitions is particularly important because they directly impact risk assessment and management practices. This paper describes how stakeholders rhetorically define and technically operationalize the risks of industrial chemicals, focusing on contemporary debates over flame retardant chemicals that in recent years have been the subject of numerous risk assessments, regulatory activities, and activist campaigns. This paper uses a multi-method approach to develop six conceptual risk formulas which delineate the components that go into evaluating risk and the relationships between those components: the classic risk formula, the emerging toxicology risk formula, the exposure-proxy risk formula, the exposure-centric risk formula, the hazard-centric risk formula, and the either-or risk formula. Using chemical alternatives assessment as an example, this analysis demonstrates how conceptual risk definitions influence the operationalization of risk assessment and management activities.