Background Tattoo inks have been reported to elicit allergic contact dermatitis. Objectives To investigate the labels and the contents of metals and pigments in tattoo inks, considering restrictions within the European Union. Methods Seventy‐three tattoo inks currently available on the market, either bought or donated (already used), were investigated for trace metals and pigments by inductively coupled plasma mass spectrometry and by matrix‐assisted laser desorption/ionization time of flight tandem mass spectrometry. Results Ninety‐three percent of the bought tattoo inks violated European, legal requirements on labeling. Fifty percent of the tattoo inks declared at least one pigment ingredient incorrectly. Sixty‐one percent of the inks contained pigments of concern, especially red inks. Iron, aluminium, titanium, and copper (most in green/blue inks) were the main metals detected in the inks. The level of metal impurities exceeded current restriction limits in only a few cases. Total chromium (0.35‐139 μg/g) and nickel (0.1‐41 μg/g) were found in almost all samples. The levels of iron, chromium, manganese, cobalt, nickel, zinc, lead, and arsenic were found to covary significantly. Conclusions To prevent contact allergy and toxic reactions among users it is important for tattoo ink manufacturers to follow the regulations and decrease nickel and chromium impurities.

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Additive manufacturing (AM) or industrial 3D printing uses cutting-edge technologies and materials to produce a variety of complex products. However, the effects of the unintentionally emitted AM (nano)particles (AMPs) on human cells following inhalation, require further investigations. The physicochemical characterization of the AMPs, extracted from the filter of a Laser Powder Bed Fusion (L-PBF) 3D printer of iron-based materials, disclosed their complexity, in terms of size, shape, and chemistry. Cell Painting, a high-content screening (HCS) assay, was used to detect the subtle morphological changes elicited by the AMPs at the single cell resolution. The profiling of the cell morphological phenotypes, disclosed prominent concentration-dependent effects on the cytoskeleton, mitochondria, and the membranous structures of the cell. Furthermore, lipidomics confirmed that the AMPs induced the extensive membrane remodeling in the lung epithelial and macrophage co-culture cell model. To further elucidate the biological mechanisms of action, the targeted metabolomics unveiled several inflammation-related metabolites regulating the cell response to the AMP exposure. Overall, the AMP exposure led to the internalization, oxidative stress, cytoskeleton disruption, mitochondrial activation, membrane remodeling, and metabolic reprogramming of the lung epithelial cells and macrophages. We propose the approach of integrating Cell Painting with metabolomics and lipidomics, as an advanced nanosafety methodology, increasing the ability to capture the cellular and molecular phenotypes and the relevant biological mechanisms to the (nano)particle exposure.