Most if not all of the pigments used in tattoo inks are manufactured for industrial use such as in printer ink and paint. Pigment manufacturers base their safety information on the assumption that the pigments are used for industrial purposes, not for tattoos.
A 2009 study analyzed 13 inks from a single supplier and found the heavy metals cadmium, cobalt, chromium and nickel in all of them. Most of the inks also contained mercury.
A 2010 analysis of black inks based on carbon found that most of them contained polycyclic aromatic hydrocarbons (PAHs) which are known to be carcinogenic.