Optimizing air-liquid interface respiratory NAM models for acute exposure scenarios to support regulatory screening and safety assessment

SOT 2026 -- New approach methodologies (NAMs) are increasingly at the forefront of inhalation toxicity assessment, supporting regulatory safety evaluation. In alignment with the FDA Modernization Act 2.0 and its April 2025 roadmap to replace, reduce and refine animal studies, advanced human-relevant approaches – such as organ-on-a-chip systems, 3D tissue models, computational modeling and in vitro assays – are being encouraged for investigational new drug (IND) applications and beyond. Creating aerosols for inhalation studies requires specialized systems tailored to the physicochemical properties of the test article. For gases, dynamic dilution and continuous-flow exposure systems are commonly used to deliver controlled concentrations under physiologically relevant conditions. Complex mixtures often employ whole-mixture generation chambers or nebulization systems that maintain chemical integrity while helping to ensure reproducible particle size distribution. Nanoparticles typically require high-precision aerosolizers such as electrospray or dry powder dispersers, which prevent agglomeration and allow control over particle size and number concentration. For fibers, rotating brush generators or fluidized bed systems are used to suspend fibers in air without altering their morphology, supporting accurate representation of inhalation exposure scenarios. These technologies are designed to deliver aerosols to in vitro platforms, supporting mechanistic studies and regulatory screening under NAM frameworks.