While red causes the most problems, most other colors of standard tattoo ink are also derived from heavy metals (including lead, antimony, beryllium, chromium, cobalt nickel and arsenic) and can cause skin reactions in some people. Sivas says the ink used for a 3 by 5 inch tattoo contains 1–23 micrograms of lead, versus the 0.5 micrograms per day permitted under Proposition 65. Understanding exposure to lead and other metals once incorporated into a tattoo is not Simple.