Modern tattoo inks vary greatly in compo- sition and can contain hazardous ingredients not originally intended for this purpose (Negi et al., 2022) and might not have a proven track record of safety in tattooing (Lehner et al., 2011; Vasold et al., 2004). Increasingly, there are concerns about tattoo ink e ects on human health, including potential carcino- genicity (Bauer et al., 2022; Desmedt et al., 2022). Additionally, it has been reported that tattoo inks can trigger acute allergic reactions immediately or lead to hypersensitivity after long-term exposure (Senaldi et al., 2016; Renzoni et al., 2018; Wang et al., 2021). For example, Klügl et al. (2010) reported that >70% of 3,411 tattooed persons experienced issues with their skin immediately or within a few weeks after getting their tattoo. More- over, allergic responses to tattoos, especially with red inks, have been reported to persist for months or years (Serup et al., 2017). Given the growing popularity of tattoos and the possibility of dangerous ingredients in tattoo products, regulations are needed to reduce the hazards caused by inappropriate tattoo inks (Wang et al., 2021). In Australia, for example, tattoo inks are not considered therapeutic materials and are not regulated by the Therapeutic Goods Administration. Instead, the National Industrial Chemi- cals Notification and Assessment Scheme (NICNAS) regulates the chemicals found in tattoo inks but typically does not legislate the import of a chemical that is used in tat- too ink if they are listed in the Australian Inventory of Chemical Substances. Little is known about tattoo ink contamination or adulteration (Musgrave, 2014); however, there is evidence of incorrect labeling. In 2016, a NICNAS report about tattoo ink composition advised that specific tattoo inks in Australia were noncompliant with regulations, marketed with incorrect ingre- dients, or not suitable for use (National Industrial Chemicals Notification and Assessment Scheme, 2018). In addition, according to a survey conducted among tattoo artists in downtown Brisbane and Melbourne Central in Australia, tattoo art- ists were unaware of the ingredients in their inks or the possible dangers associated with them (Matsika et al., 2016). In Europe, tattoo inks are regulated by the European Union’s General Product Safety Directive. According to this directive, a pro-
ducer is required to place only safe items on the market, and a comprehensive list of con- tents must be included on the product label, which is accomplished through classification, labeling, and packaging (Minghetti et al., 2019; Negi et al., 2022). In 2011, an analysis by Hauri (2011) reported finding 34 prohibited pigments in 30 tattoo ink samples. The pigment green 36 (PG36, C.I. [color index] 74265) was declared in three green inks, but the samples were dem- onstrated to include the prohibited pigment green 7 (PG7, C.I. 74260). Furthermore, a yellow and a blue pigment were stated for one ink, but the ink was again found to contain PG7, not the stated yellow and blue pigments. The ingredient list on a violet ink was incor- rect: The ink included the pigment white (tita- nium dioxide [TiO 2 ]) and the pigment blue 15 (PB15, C.I. 74160), which when combined produce a light blue. And the violet color was shown to be created with the prohibited pig- ment violet 23 (PV23, C.I. 51319). Concerningly, mislabeling and undeclared ingredients continue to persist in commercial formulations of tattoo ink. A study by Poon et al. (2008) examining 190 tattoo inks indicated that 37% of the inks included prohibited sub- stances and 53% contained >1 of A) excessive levels of nitrosamine, B) unreported material, or C) claimed material that was not found in the ink. More than a decade later, Wang et al. (2021) reported that for 50% of the tattoo inks they tested, labeling inaccurately stated at least one pigment component. Furthermore, a study by Moseman et al. (2024) showed major discrepancies between tattoo ink composition and ingredient labels, especially for the non- pigment components (e.g., carrier, vehicle). Regarding tattoo safety and the possibility of allergic sensitization, it is likely that some pig- ments have been removed from the ink formu- lations due to EU regulations banning specific pigments in tattoo inks (Kiszla et al., 2023; Wang et al., 2021). Identifying pigments in commercial tat- too inks presents a large challenge due to the inks’ complex composition, diverse combi- nations of pigments used to achieve subtle colors, poor solubility of pigments in tradi- tional solvents, and other additives present that enhance pigment dispersion (Bauer et al., 2019). Studies have primarily relied on mass spectrometry (MS) for pigment analy- sis. Both Hauri (2011) and Wang et al. (2021)
used MALDI-TOF MS to identify pigments in tattoo inks; however, this approach has limitations. For example, Wang et al. (2021) showed that some pigments were unable to be detected using MALDI-TOF MS due to poor ionization and or low mass. Further- more, MS-based techniques often require extensive sample preparation, making the analysis time-consuming and challenging for label compliance assessments. Given the complex and varied chemical nature of tattoo ink ingredients, our study aimed to develop a novel approach for pig- ment identification by applying a combina- tion of spectroscopic techniques. Unlike previous studies that primarily analyze tattoo inks after extensive pretreatment, digestion, or extraction, our approach focused on exam- ining inks in their dried, untreated state or with minimal sample preparation. Compared with MS, spectroscopic techniques such as infrared (IR), nuclear magnetic resonance (NMR), X-ray di raction (XRD), Raman, and energy dispersive X-ray (EDX) enable rapid, minimally destructive analysis of pig- ment molecular structures, crystallinity, and elemental composition with minimal sam- ple preparation requirements (Bauer et al., 2019, 2020; Moseman et al., 2024). Although most prior research uses these techniques in isolation, our study leveraged the com- bined information from spectroscopic and elemental analysis techniques of IR, NMR, XRD, Raman, EDX, and inductively coupled plasma optical emission spectroscopy (ICP- OES) to rapidly assess the pigment composi- tion of a set of yellow inks that have not been examined previously.
Methods
Materials and Instruments INTENZE brand lemon yellow (LY), golden yellow (GY), golden rod (GR), and bright orange (BO) tattoo inks were purchased from Tattoo Direct in Victoria, Australia. Pigment yellow 14 (PY14, C.I. 21095, 97% purity); pigment yellow 65 (PY65, C.I. 11740, 98% purity); pigment white (titanium dioxide [TiO 2 ], C.I. 77891, 99.5% purity); pigment blue 15 (PB15, C.I. 74160, technical grade); pigment orange 13 (PO13, C.I. 21110, tech- nical grade); and barium sulfate (BaSO 4 , C.I. 77120, 99% purity) were purchased from AK Scientific in Union City, California. Methy-
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September 2025 • Journal of Environmental Health
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