From Reduction to Replacement: Challenges and Proposed Solutions for Animal-Free Safety Assessment of Hydrocarbon UVCB Substances.

The European Commission (EC) developed a Roadmap to phase out animal testing, with milestones and practical steps across 15 different European chemical legislations (EC 2026). Currently though, the number of animals used for compliance testing in the EU remains high, particularly for high-volume chemicals such as Petroleum Substances, and is expected to increase with the introduction of new hazard classes under Regulation (EC) 1272/2008 (CLP). A reduction in animal testing for these substances can be achieved today by grouping, read-across and composition-activity models leveraging historical data and an in-depth understanding of substance composition and manufacturing processes. However, full replacement with New Approach Methodologies (NAM) remains challenging due to the complexity and physico-chemical properties of hydrocarbon substances from conventional and renewable feedstocks which are UVCB substances (Unknown, Variable composition, Complex reaction products or Biological materials). This manuscript outlines the current efforts to reduce animal testing in environmental and human health assessment of hydrocarbon UVCB and highlights key challenges limiting broader application of in silico and in vitro approaches. To address these challenges, we propose a pragmatic and readily implementable roadmap for the transition to animal-free UVCB assessment, adapting the different elements of NAM frameworks including analytical characterization, in silico predictions, in vitro testing, and in vitro-in vivo extrapolation. Short-term actions focus on enhancing read-across and increasing regulatory acceptance of existing approaches, mid-term priorities include improving technical readiness of in vitro testing and in silico approaches and the long-term goal aims at integrating predictive models and the development of an animal-free UVCB framework for regulatory acceptance. This transition will require tailored approaches and is expected to follow a different timeline compared to other industrial chemicals.