Population doubling levels (PDLs).

<p>PDLs of SM-exposed patients and controls were compared at each passage performed at different time points after the start of the primary culture. Each individual culture's PDL was presented by a red dot. PDL of the SM-exposed patients were significantly higher than controls from the day 7 through 28, but did not show any significant difference on the day 35. * p = 0.0025, ** p = 0.0001, *** p < 0.05.