ICG is decomposed by light within a self-sensitized photo oxidation. The decomposition products reduce the viability of RPE cells in vitro. The toxic effects of decomposed ICG should be further investigated under in vivo conditions.
In the past years, tattoos have become very popular worldwide, and millions of people have tattoos with mainly black colours. Black tattoo inks are usually based on soot, are not regulated and may contain hazardous polycyclic aromatic hydrocarbons (PAHs). Part of PAHs possibly stay lifelong in skin, absorb UV radiation and generate singlet oxygen, which may affect skin integrity. Therefore, we analysed 19 commercially available tattoo inks using HPLC and mass spectrometry. The total concentrations of PAHs in the different inks ranged from 0.14 to 201 lg ⁄ g tattoo ink. Benz(a)pyrene was found in four ink samples at a mean concentration of 0.3 ± 0.2 lg ⁄ g. We also found high concentrations of phenol ranging from 0.2 to 385 lg ⁄ g tattoo ink. PAHs partly show high quantum yields of singlet oxygen (F D ) in the range from 0.18 to 0.85. We incubated keratinocytes with extracts of different inks. Subsequent UVA irradiation decreased the mitochondrial activity of cells when the extracts contained PAHs, which sufficiently absorb UVA and show simultaneously high F D value. Tattooing with black inks entails an injection of substantial amounts of phenol and PAHs into skin. Most of these PAHs are carcinogenic and may additionally generate deleterious singlet oxygen inside the dermis when skin is exposed to UVA (e.g. solar radiation).
Millions of people are tattooed with inks that contain azo pigments. The pigments contained in tattoo inks are manufactured for other uses with no established history of safe use in humans and are injected into the skin at high densities (2.5 mg/cm(2)). Tattoo pigments disseminate after tattooing throughout the human body and although some may photodecompose at the injection site by solar or laser light exposure, the extent of transport or photodecomposition under in vivo conditions remains currently unknown. We investigated the transport and photodecomposition of the widely used tattoo Pigment Red 22 (PR 22) following tattooing into SKH-1 mice. The pigment was extracted quantitatively at different times after tattooing. One day after tattooing, the pigment concentration was 186 microg/cm(2) skin. After 42 days, the amount of PR 22 in the skin has decreased by about 32% of the initial value. Exposure of the tattooed skin, 42 days after tattooing, to laser light reduced the amount of PR 22 by about 51% as compared to skin not exposed to laser light. A part of this reduction is as a result of photodecomposition of PR 22 as shown by the detection of corresponding hazardous aromatic amines. Irradiation with solar radiation simulator for 32 days caused a pigment reduction of about 60% and we again assume pigment decomposition in the skin. This study is the first quantitative estimate of the amount of tattoo pigments transported from the skin into the body or decomposed by solar or laser radiation.
In conclusion, high concentrations of colourants are injected into the skin during tattooing and based upon this quantification, a risk assessment of tattooing ought to be carried out.
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