Skin sensitization and systemic quantitative risk assessment of nickel in tattoo ink.

Prolonged dermal exposure to nickel (Ni), a heavy metal found in tattoo ink, is associated with allergic contact dermatitis and skin sensitization in susceptible individuals. Although the systemic toxicity of Ni following inhalation and dermal exposure has been documented, limited information exists on the toxicological effects of intradermal exposure. Therefore, this study conducted a risk assessment to evaluate the potential for skin sensitization induction and non-cancer systemic toxicity from intradermal exposure to Ni-containing tattoo ink. A systematic literature review was performed to identify studies relevant to intradermal Ni exposure from tattoo ink. Risk characterization was conducted using margin of safety (MOS) calculations for dermal and systemic exposure scenarios. The dermal MOS was calculated by dividing the acceptable exposure level (AEL) by the consumer exposure level (CEL). The AEL was calculated by applying a safety assessment factor of 300 to the Ni no expected sensitization induction level (NESIL) of 401.07 μg/cm2/day. The systemic MOS was calculated by dividing the systemic exposure dose (SED) by an adjusted Office of Environmental Health and Hazard Assessment oral reference exposure level (REL) of 0.0044 mg/kg, accounting for the 40% oral bioavailability. For dermal exposure, the AEL (1.34 μg/cm2) exceeded the CEL (0.03 μg/cm2), yielding an MOS of 44.67. For systemic exposure, the SED (0.000027 mg/kg/day) was below the adjusted REL, yielding an MOS of 162. Sensitivity analyses confirmed MOS values greater than 1. Skin sensitization and non-cancer systemic toxicity are not expected from exposure to Ni in tattoo ink.