Metabolic activity
The metabolic activity of BEAS-2B and A549 cells was analysed using the MTT test on 96-well plates. The absorbance was detected at 570 nm using a spectrophotometric plate reader and the proportion of metabolically active cells was calculated as a percentage from corresponding readings of the blank control cells. The absorbance of the PM was measured in blank samples at the different concentrations and adjusted for in the calculations.