Fig. 5

DNA strand breaks assessed by the comet assay in BEAS-2B cells after a 24-h exposure to coarse (A–J), medium (B–K) and fine (C–L) size fractions of U-CNF (A–C), T-CNF (D–F), C-CNF (G–I) and E-CNF (J–L). Data are expressed as percentage of DNA in tail and presented as the mean ± se (N = 2 independent experiments). Asterisks designate statistically significant differences compared with the untreated cultures at **p < 0.01 and ****p < 0.0001. Daggers designate statistically significant linear regression at ^††††p < 0.0001. The positive control, H₂O₂ (20 mM), induced a statistically significant increase in the percentage of DNA in tail over the negative control values in all the experiments performed (15.2 ± 1.1-fold increase; p < 0.02) confirming the validity of the experiments (data not shown)