,At its 41st meeting in December 2025, the ECHA-hosted PBT Expert Group discussed recent scientific advances in bioaccumulation (B) assessment, with a strong focus on integrating New Approach Methodologies (NAMs). Updated ECHA guidance (IR&CSA Chapter R.11 and CLP environmental hazards) now moves beyond the traditional fish-centric aquatic focus to include non-vertebrate species such as Hyalella and to incorporate toxicokinetic data relevant for air-breathing organisms. These developments respond to concerns that some substances may not bioaccumulate in fish but can accumulate in mammals and other air-breathers, posing risks to apex species and ecosystem stability. Key outcomes were presented from the UBA-funded project Integrated strategy for the assessment of aquatic and terrestrial bioaccumulation (20222025). Based on a dataset of 231 diverse chemicals, the project found no single superior method for predicting log Kow or log Koa and recommended consensus values derived from multiple independent approaches. The proposed tiered strategies emphasize alternative and non-vertebrate methods, including QSARs, in vitro clearance assays (OECD TG 319 A/B), invertebrate bioconcentration testing (OECD TG 321), and IVIVE for air-breathing organisms, with in vivo testing reserved for inconclusive cases. Case studies demonstrated that, for most substances, reliable non-vertebrate or alternative test options are already available, highlighting the importance of understanding NAM applicability domains to strengthen confidence in regulatory decision-making.
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