Tat_BioV: tattoo ink exposure and biokinetics of selected tracers in a short-term clinical study of 24 subjects

Abstract

About one-fifth of people in industrialised countries are tattooed, potentially putting them at risk of exposure to possible carcinogenic or otherwise harmful substances. This study aims to determine the exposure to soluble tattoo ink ingredients and their excretion within 24 h after tattooing. In this clinical study, 24 subjects were tattooed with black or red tattoo ink to which the 3 tracer substances, potassium iodide, 4-aminobenzoic acid (PABA) and 2-phenoxyethanol (PEtOH), had been added to mimic known substances found in tattoo inks. Tracers and their metabolites were quantified in blood, urine, ink and consumables pre- and post-tattooing. Tattooed skin area was determined using picture analysis. PABA metabolism upon tattooing was compared to peroral administration. Skin fibroblasts and macrophages were tested in vitro for their ability to metabolise PABA. All tracers or their metabolites were identified in urine; iodide and the PABA metabolite 4-acetamidobenzoic acid (ACD) were identified in plasma. The worst-case scenario for systemic ink exposure was estimated to be 0.31 g ink per tattoo session (75th percentile). Peroral administration resulted in lower levels of ACD than tattooing. Fibroblasts and macrophages were capable of converting PABA into ACD. Our results are the first human in vivo data on soluble tattoo ink ingredients and suggest that the overall exposure might be lower than the estimates previously used for regulatory purposes. In addition, the first-pass effect by skin metabolism leads to an altered metabolite profile compared to oral exposure. Skin metabolism might also contribute to detoxification of certain carcinogenic substances through N-acetylation.

Keywords: Clinical study; Environmental exposure; Mass spectrometry; Metabolism; Skin; Tattooing.

Fig. 1

Study sampling and exposure calculation. A Overview of sampling times for blood and urine during the 48-h study period. B Calculation of the hypothetical ink amount used per session (hypo) based on ink weighing and iodine quantification in the consumables. C Calculation of the systemic ink amount per session (sys) calculated by excreted tracers in urine C-F. Background levels in urine A–B were subtracted

Fig. 2

A–C Comparison of ink per session (hypo), tattooed skin area and ink per area of all subjects (n = 22), ink per session calculated from mass difference of ink bottle weight and subtracted ink residues from consumables. The box and whisker plots show median (line) and mean ( +) for all, black or red tattooed subjects. D The amount of tattoo ink per area is positively correlated with the ink use per session (systemic, sys, based on excretion of 4-aminobenzoic acid, PABA) with the slope being higher for red tattoos. E Ink per area (sys, PABA) is negatively correlated with the tattooed area. F Correlation plot of tracer retrieval to mean retrieval calculated for each subject. For D–F, regression line was calculated with a linear model (x ~ y) and the 95% confidence interval was plotted in grey

Fig. 3

Pictures of tattoos from the study. A Black tattoo of subject Black 5 with the highest urine retrieval. B The black outlines of subject Red 9 were tattooed beforehand and did not contain any tracers. C Tattoo in (B) with red areas. Blood samples were drawn shortly before and at specific time points after the start of tattooing with red ink containing the tracers. D Wound dressing of a red study subject displays exudation of black and red tattoo ink within the first hours after tattooing. © Artist: Alexander Pietsch (A), Carlo Sohl (B,C)

Fig. 4

Analysis of 4-aminobenzoic acid (PABA), 2-phenoxyethanol (PEtOH) and their metabolites. A Metabolism of PABA. GLYAT: glycine-N-acyltransferase. NAT: N-acetyltransferase. UGT: UDP-glucuronosyltransferase. B Metabolism of PEtOH. ADH: Alcohol dehydrogenase. ALDH: aldehyde dehydrogenase. C Comparison of the metabolite distributions in total urine (urine C–F) calculated from raw peak area ratios. Data are displayed for three tattoo study subjects (Black 8, Black 10, Red 5) and the three peroral PABA subjects for the first 24 h after tattooing