Indirect DNA damage

Indirect DNA damage occurs when a UV-photon is absorbed in the human skin by a chromophore that does not have the ability to convert the energy into harmless heat very quickly.

[2] Melanin[dubious – discuss] [citation needed] and DNA have extremely short excited state lifetimes in the range of a few femtoseconds (10−15s).

[3] The excited state lifetime of compounds used in sunscreens such as menthyl anthranilate, avobenzone or padimate O is 1,000 to 1,000,000 times longer than that of melanin,[2] and therefore they may cause damage to living cells that come in contact with them.

The bimolecular reactions that cause the indirect DNA damage are illustrated in the figure: 1O2 is reactive harmful singlet oxygen: Unlike direct DNA damage, which occurs in areas directly exposed to UV-B light, reactive chemical species can travel through the body and affect other areas—possibly even inner organs.

[dubious – discuss] The traveling nature of the indirect DNA damage can be seen in the fact that the malignant melanoma can occur in places that are not directly illuminated by the sun—in contrast to basal-cell carcinoma and squamous cell carcinoma, which appear only on directly illuminated locations on the body.

Indirect DNA damage: The chromophore absorbs UV-light (* denotes an excited state), and the energy of the excited state is creating singlet oxygen ( 1 O 2 ) or a hydroxyl radical (•OH), which then damages DNA through oxidation. [ 1 ]