On Jul. 2, 2024, a study was released that showed evidence that commercial tattoo and PMU inks are frequently contaminated with pathogenic microorganisms. No significant association was found between sterility claims on the ink label and the absence of bacterial contamination. The results indicate that tattoo and PMU inks can also contain anaerobic bacteria.

The findings, published in Applied and Environmental Microbiology revealed that unopened and sealed tattoo inks can harbor anaerobic bacteria, known to thrive in low-oxygen environments, such as the dermal layer of the skin, alongside aerobic bacteria.