A perspective on Seveso accident based on cause-consequences analysis by three different methods

Seveso incident happened on Saturday 10th July 1976 within the production plant of 2,4,5-trichlorophenol at the ICMESA factory represents a watershed because it gave off a specific legislation in the field of safety regarding activities subjected to Major Accident Hazards (MAH) and the handling of dangerous substances. Although the severity of the mishap, still nowadays the real cause of the accident remains, at least partially, shrouded in uncertainty and different mechanism hypotheses were proposed. These doubts could lead considering Seveso mishap as a “black swan” incident, i.e. an improbable event characterized by three peculiarities: it is not expected; it has an extreme impact; it is explainable and predictable after the fact. Further investigation appears to be essential, analyzing the available material and processing a deep analysis towards several methods, which provide different views and interpretations of the fact. To this purpose, three methods were selected: AcciMap approach; the Energy Barrier Model; the System-Theoretic Accident Model & Processes (STAMP) coupled with a dynamic approach. The last part of this work is dedicated to a specific modelling of the incident through system dynamics technique using a customized framework covering technical, human and organizational aspects.