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Characterization of coal tattoos by Raman spectroscopy

THE IDENTIFICATION of tattoo pigments could be useful for dermatologists in case of allergic adverse reaction or for laser tattoo removal, but it is often difficult to identify them because ink manufacturers often do not disclose ingredients in their products. Moreover, the chemical composition of tattooing pigments continuously changes over time according to available technologies and materials (1). Natural colored metallic compounds and salts have been progressively substituted by synthetic organic pigments that possess superior light fastness, resistance to enzymatic digestion and are available in a wider range of hues (1). Our group recently described the application of Raman micro-spectroscopy for the characterization of cutaneous foreign bodies (2, 3) and of endogenous material crystals accumulated in the skin in case of metabolic disorders (4). Poon et al. (1) demonstrated that it is possible to identify organic tattoo pigments using Raman microspectroscopy in cryo-sectioned pig skin samples. We describe two cases where Raman Spectroscopy signatures identified the pigment of the tattoos of two coal-miners. Two skin biopsies of 4 mm were taken from two dark lesions from two 77-year-old male subjects that had been presenting linear black Fig. 1. Clinical appearance of the cutaneous pigmentations of the two minors.