Systems toxicology assessment of a representative e-liquid formulation using human primary bronchial epithelial cells.

•A 3-step approach combining 1) real-time cytotoxicity, 2) high-content screening and 3) gene expression analysis was developed in NHBE cells.•Different scoring methods were developed enabling a ranking based on cytotoxicity, phenotypic outcome, and molecular network perturbations.•Flavoring substances that potentially contribute greatly to the overall mixture effect were identified (citronellol and alpha-pinene).•Most of the cytotoxic effect appeared to be attributable to citronellol, with the remaining substances contributing due to synergistic effects.•This case study underlines how testing both individual flavoring substances and mixtures are essential for a clear assessment of e-liquids.