Next generation risk assessment of hair dye HC yellow no. 13: Ensuring protection from liver steatogenic effects

Pros, cons & Future potential

• - This NGRA integrates multiple New Approach Methodologies (NAMs), including in vitro hepatocellular assays, in silico modelling, and PBK-based exposure estimation, to provide a fully animal-free, exposure-led safety assessment.
• - It demonstrates how a mechanistic and tiered weight-of-evidence approach can ensure consumer protection while aligning with EU regulatory requirements.
• - The method allows identification of liver steatosis potential at human-relevant concentrations, improves mechanistic transparency through AOP-based reasoning, and reduces uncertainty by combining diverse data streams.

• - The workflow’s main limitation lies in the current lack of validated and harmonised in vitro assays for repeated-dose liver toxicity.
• - Quantitative integration of in vitro bioactivity with PBK-derived internal concentrations still relies on assumptions about metabolic competence and the relevance of chronic exposure.
• - Data curation and interoperability between computational and experimental layers remain technically demanding, and regulatory acceptance of integrated NGRA frameworks is still evolving.

• - Ongoing work focuses on extending the approach to include omics-based mechanistic profiling, sensitivity analysis of PBK parameters, and integration with knowledge graph tools, such as TOXIN-KG, to support read-across justification.
• - Future refinements will focus on improving the linkage between in vitro kinetics, exposure duration, and apical outcomes to strengthen quantitative risk characterisation.
• - Cross-laboratory testing could enhance reproducibility and reliability for regulatory use.

• - The method can be adapted for other cosmetic ingredients or industrial chemicals where hepatotoxicity, steatosis, or metabolic disruption are relevant endpoints.
• - It is also applicable to broader NGRA case studies for repeated-dose systemic toxicity, helping to establish practical workflows for safety substantiation under the EU Cosmetics Regulation and REACH.
• - With further optimisation, the framework could contribute to next-generation risk assessments across different organs and product sectors.