HAP induces DNA breaks in human cells. The effect of HAP and 100 μM hydrogen peroxide on the frequency of single-stranded breaks recorded at the end of treatment in WI-38, HCT116 and P32T cell cultures by single-cell electrophoresis at pH > 13. (a) Analysis of the concentration-dependent effects of HAP and hydrogen peroxide on the frequency of DNA strand breaks in WI-38, HCT116 and P32T cells. The damaging DNA-agent dose responses are plotted on the x-axis. The mean percent DNA in the comet tail is plotted on the y-axis as a ratio of the amount of DNA in the comet tail/the amount of DNA in the whole comet. The insert in the upper part of the plot is a linear plot of this correlation for each culture. Results are shown as means ± standard error of results of six different experiments. The level of statistical significance was set at P < .05. (b) Micrographs of WI-38 (a, b, c), HCT116 (d, e, f), and P32T (g, h, i) cells treated with different doses of HAP: 0 (a, d, g), 0.66 mM (b, e, h) and 3.3 mM (c, f, i) for 24 hr. Bar—10 μm.