Upon simultaneous illumination by UV and visible light, the observation of ·DMPO-OH can result from the decay of ·DMPO-OOH, in its turn resulting from O2 -formation, and may provide evidence of the pathway of H2O2 formation. Additionally, the observation of DMPO-X can also result from oxidation due to excess of ·OH and other radicals or due to higher H2O2 photolysis under simultaneous excitation. Another source of ·OH radicals leading to ·DMPO-OH and DMPO-X upon simultaneous illumination at 385 and 532 nm can be the excess ·OH radicals that did not react with the medium. Alternatively, excess electrons can react back with H2O2 to produce H2O and ·OH. While EPR may not provide a fully detailed picture of the ongoing processes, the fact that ·OH radicals and oxidation of the spin adduct are only observed