Tattoo Pigments are Cleaved by Laser Light-The Chemical Analysis In Vitro Provide Evidence for Hazardous Compounds¶
ABSTRACT
In the western world, more than 80 million people decorate their skin with tattoos. Tattoo colorants are injected into the skin, like medical drugs. Most tattoo colorants are industrial pigments, and chemical industries have never produced them for human use but only to stain consumer goods. Up to 10% of tattooed people request removal of their tattoos because of an improved self-image or social stigmatization. In contrast to tattooing, physicians usually perform the tattoo removal. For that purpose laser light at very high intensities irradiates the skin to destroy the tattoo pigments. Based on a recent analysis of tattoo pigments, two widely used azo compounds were irradiated in suspension with laser and subsequently analyzed by using quantitative high-performance liquid chromatography and mass spectrometry. The high laser intensities cleaved the azo compounds, leading to an increase of decomposition products such as 2-methyl-5-nitroaniline, 2-5-dichloraniline and 4-nitro-toluene, which are toxic or even carcinogenic compounds. Moreover, the results of the chemical analysis show that the tattoo colorants already contain such compounds before laser irradiation. Because of a high number of patients undergoing laser treatment of tattoos and based on the results of our findings in vitro, it is an important goal to perform a risk assessment in humans regarding laser-induced decomposition products.
Abbreviations: CR, Cardinal Red; 2,5-DCA, 2-5-dichloroaniline; 1,4-DCB, 1-4-dichlorobenzene; HPLC, high-pressure liquid chromatography; 2-MNA, 2-methyl-5-nitroaniline; 4-NT, 4-nitrotoluene.
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INTRODUCTION
In the western world, tattooing seems to be a sign of selfdestructive and rebellious behavior (1). Millions of people have at least one decorative tattoo. Cosmetic tattoos, to mimic eye, lip or eyebrow liner, have also become increasingly popular (2).
In the past, coloring agents were inorganic pigments, whereas for dark blue amateur tattoos, commercially available ink is still in use. Because tattoo compounds in comparison with cosmetics are not officially controlled, the origin and chemical structure of these coloring agents are hardly known. Consequently, neither the tattoo artist nor the tattooed patient has any information about the compounds punctured into the skin.
Recently, an extensive analysis of a large number of tattoo compounds was performed for the first time (3). Most of the commercially available tattoo compounds are organic pigments classified by their chemical constitution (4).
Generally, the tattoo pigments are well tolerated by the skin. Nevertheless, adverse reactions have been published in the literature (5-8). Moreover, several malignant lesions have occurred in tattoos (maybe coincidental) (9-11). Because of an improved self-image or social stigmatization, a significant number of people undergo a therapy of tattoo removal by using predominantly Q-switch lasers. Most of the tattoo pigment is found within cells and not free within the dermis. Although many pigment particles measure “a few microns,” others are significantly larger (12) or when accumulated within cells may act as larger aggregate bodies. According to the principles of selective photothermolysis (13), the laser impulses show a high intensity and ultrashort pulse durations of a few nanoseconds (Q-switched lasers). The laser pulses change the shape and the size of the tattoo particles abruptly as proved by histology (12).
However, the exact mechanisms of action regarding the destruction of tattoo pigments are still unclear. After being absorbed in the pigment molecule, the energy of the laser light is converted to heat or breaks chemical bonds inside the molecule. The ultrashort heating (ca in ns) of the pigment may lead to disruption of the pigment. At the same time, the extremely hot surface of the pigment leads to a rapid expansion of the surrounding water, inducing negative pressure and a shock wave near the surface of the pigment. As demonstrated for a suspension of small particles in water, these shock waves may help destroy the tattooed compounds (14).