Development of an in vitro acute respiratory toxicity test using the SoluAirway™, 3D human airway model

This study presents a novel in vitro method for acute respiratory toxicity testing using the SoluAirway™ model (SoluAirway™ ARTT). SoluAirway™ is a 3D human airway tissue model constructed from primary human nasal epithelial cells, recapitulating the structural and molecular characteristics of the human bronchial epithelium. Tissues were exposed to four concentrations of test chemicals using two application methods—vapor-cap and direct application—for 4 h, followed by a 20 h post-incubation. Tissue viability was assessed using the MTT assay. Following established classification approaches, EC₅₀ and EC₂₅ values were determined and used to assign GHS acute inhalation toxicity categories: EC₂₅/₅₀ ≤ 5 mg/tissue: GHS Category 1 or 2, 5 < EC₂₅/₅₀ ≤ 25 mg/tissue: GHS Category 3 or 4 and EC₂₅/₅₀ > 25 mg/tissue: No Category. The direct application method showed an excellent predictive accuracy of 76.92 % (10/13). When 20 additional reference chemicals (33 total) were tested, the EC₅₀-based classification achieved a predictive accuracy of 75.76 % (25/33). Notably, applying a fixed-dose viability threshold (≤50 % viability at 5 mg/tissue for GHS 1/2; >50 % at 5 and ≤ 50 % at 25 mg/tissue for GHS 3/4; others as No Category) yielded comparable predictive performance. Collectively, these results suggest that SoluAirway™ ARTT is a promising, cost-effective alternative method for assessing acute inhalation toxicity.