Influences of age groups (year-olds) on the frequencies (%) of moderate and high DNA damage of the total group. N = sample size. The data correspond to the means and to the standard error of mean (SEM) of the frequencies (%) of comets of class 1 and 2 (moderate damage) and of comets of class 3 and 4 (elevated damage) with respect to the total damages. P-values were generated by the Kruskall-Wallis test. The lower-case letters indicate significant differences between the age groups detected by the Mann-Whitney U test in the 2-to-2 comparisons: for moderate damage, a = significant compared to b: p = 0.014 in the comparison of 20-40 and 41-56 year-olds; for elevated damages, c = significant compared to d: p = 0.044 in the comparison of 17-19 and 41-56 year-olds and p = 0.008 in the comparison of 20-40 and 41-56 year-olds.