Risk assessment of chemicals can be based on toxicology and/or epidemiology. The choice of toxicological or epidemiological data can result in different health-based guidance values (HBGVs). Communicating the underlying argumentation is important to explain these differences to the public and policymakers. In this article, we explore the argumentation used to justify the use of toxicological or epidemiological data in the derivation of HBGVs in four different risk assessments for the chemical Perfluorooctanoic acid (PFOA). The pragmadialectical argumentation theory (PDAT) is hereby applied. The argumentations to select relevant health endpoints or certain studies to infer causality appeared mainly based on "symptomatic relations," that is, study results are used as characteristic of what was claimed to be a causal relation without delving into the actual causal argumentation that preceded it. Starting points that are at the basis of the chain of arguments remained implicit. Argumentation to use epidemiological and/or toxicological data was only briefly mentioned and the underlying argumentative foundation that led to the conclusion was seldom found or not addressed at all. The decision to include/exclude information was made based on the availability of data, or the motives for the choice remained largely unclear. We conclude that more depth in argumentation and a subordinative chain of arguments is needed to better disclose the underlying reasoning leading to a certain health-based guidance value (HBGV). More explicit identification and discussion of starting points could be a valuable addition to general risk assessment frameworks for maximum use of toxicological and epidemiological data and shared conclusions of the assessment.