Altered canonical pathways. A549 cells (n = 3) were exposed for 24 h and 72 h to increasing concentrations of fumed silica AEROSIL® 200 NPs (3.0 and 6.0 μg/cm2). Seven relevant canonical pathways disturbed after 24 h and 72 h exposure with two doses of NPs (3.0 and 6.0 μg/cm2) were revealed with the Ingenuity Pathway Analysis tool. Each canonical pathway is constituted of a finite number of genes. For each dose and time point, we calculated a ratio indicating the percentage of altered genes in our dataset belonging to a given canonical pathway. These pathways are all significant according to a Fisher statistical test (p-value < 0.05).