Effect of sustained L1 exposure on iron/hydrogen peroxide–mediated DNA single-strand breaks. Iron-loaded liver cells were incubated in 1 mmol/L L1 for 1 hour, followed by exposure to 100 μmol/L hydrogen peroxide for 30 minutes during which exposure to 1 mmol/L L1 was maintained. Illustrated is a representative experiment performed in duplicate and the values obtained were averaged. Shown are DNA single-strand breaks in control cells exposed to media alone, iron-loaded cells exposed to hydrogen peroxide, and iron-loaded cells exposed to hydrogen peroxide in the presence of L1.