Preventing regrettable substitutions: a proposal for a tiered testing approach for BPA alternatives under the PARC initiative.

Bisphenol A (BPA) alternatives are increasingly used in the manufacture of industrial and consumer products, following regulatory restrictions on BPA. However, insufficient safety data on these substitutes raise concern as regards potential regrettable substitutions. Under the EU Partnership for the Assessment of Risks from Chemicals (PARC), Work Package 5 (WP5) addresses this challenge by applying a human-relevant tiered hazard assessment strategy grounded on OECD test guidelines as first tier and expanding the battery to include NAMs (New Approach Methodologies). Eight BPA alternatives were prioritized for studies addressing key toxicological endpoints, namely, endocrine disruption (ED), developmental neurotoxicity (DNT), immunotoxicity, genotoxicity and carcinogenicity and metabolic fate examination (detoxification vs. potential bioactivation), to enable early identification of biological activity and support cross-endpoint prioritization. This manuscript describes the structure and implementation of the testing framework. This integrated testing strategy proposes a structured approach to identify substances of potential concern, guide targeted higher-tier studies, and support regulatory prioritization. PARC WP5 framework is testing whether coordinated NAM-based methods may contribute to next-generation risk assessment and help prevent regrettable substitutions among BPA alternatives for rapid regulatory adoption. Detailed experimental results will be reported separately upon completion of the project.