The relative expression levels of HMOX1 in A549 cells treated with concentrations of 500 µg/ml (red) and 50 µg/ml (green) of a cherry stone sample, collected with lubricant (A), cherry stone sample, collected without lubricant (B), and wheat straw sample, collected with lubricant (C), are presented as normalized expression (ΔΔCq), relative to the control (untreated cells), using β-actin as a reference gene.