A critical assessment of software tools for Human Health Risk Assessment: Comparative study of RBCA and Risk-net =

Human Health Risk Assessment (HHRA) is a fundamental step in the management of contaminated sites, linking site characterization with the design of soil and groundwater remediation. Given the complexity of exposure scenarios and the uncertainties in evaluating potential health effects, specialized software has become an essential tool for institutions and consultants. This thesis presents a critical comparison of two widely used programs, RBCA Tool Kit® and Risk-net®, both based on ASTM methodologies but designed for different contexts. The analysis is structured in three stages. First, the HHRA process is reviewed, highlighting hazard identification, exposure assessment, toxicity assessment, and risk characterization, with emphasis on the role of software in managing complex data. Second, the two tools are described, focusing on their design and underlying assumptions. Third, a direct comparison is carried out, examining exposure pathways, contaminant parameters, volatilization and leaching models, groundwater dispersion, baseline risk estimation, and cleanup levels. The comparison shows that RBCA provides broader databases and greater flexibility in modelling contaminant transport, making it suitable for complex and international applications. However, it is less intuitive, requires a paid license, and depends on Microsoft Excel. Risk-net, by contrast, is free, faster to use, and well aligned with Italian regulations, but offers fewer contaminants in its database and limited modelling options, which may restrict its applicability outside its regulatory context. To validate the comparison, both programs were applied to theoretical case studies involving on-site and off-site scenarios. Results confirm that, while general risk characterizations are consistent, differences in fate and transport assumptions and in chemical parameter values can lead to divergent cleanup targets, potentially influencing remediation strategies and costs. In conclusion, RBCA and Risk-net should not be considered interchangeable. RBCA is preferable in projects requiring detailed modeling and flexibility across different regulatory environments, whereas Risk-net is best suited for rapid and standardized assessments within the Italian framework. By clarifying strengths, weaknesses, and selection criteria, this thesis provides decision-makers with a practical reference for choosing the most appropriate tool and ensuring more reliable human health risk assessments.