From the Archives – Science behind Tattoos

One of more popular topics that All About Science covered in the Ponca City News was the science behind tattoos. Ultimately, this topic was covered in an expanded article for InChemistry, and other interviews. Here is the original column.

What do Otzi, the iceman; a Peruvian mummy, and Kat Von D all have in common?  They are all inked.  Tattooing, it seems has always been a part of human history and there are a variety of reasons why a person might get a tattoo.  Most of Otzi’s tattoos are located near his joints, which have caused speculation that they may be been associated with a treatment for arthritis.  Other tattoos are culturally driven such as those used by native peoples throughout the world.  Still others are associated with personal expression. But, have you ever really thought about those inks?  Or, the chemistries that may be involved in the overall process? How safe are they? 

According to a recent JRC report (insert report title), over 12% of the population of Europe has a tattoo and in the United States and Canada the percentage is approaching 24%.  And, for those between the ages of 18 and 40 in the U.S., approximately 1 in 3 are likely to have at least one tattoo.  This is the same age demographic that seems to be trending toward organic foods and removal of potentially toxic additives to foods and plastic. But, do they know what is actually in the inks that are being used to create the patterns on their skin?

The regulations associated with tattooing are varied and tend to be associated with the location and licensing of the tattoo parlor and when a person can legally consent to getting a tattoo.  (You can find a list of regulations by state here.) As the primary risk being monitored under these regulations is the possibility of infection or the transmission of disease through unsanitary procedures or conditions. But, when it comes to the inks, there is very little regulatory oversight.  The Food and Drug Administration is nominal responsible in the U.S. and the JRC report outlines the regulatory climate in Europe.   Additionally, until recently there was very little information about the potential risks from the ingredients in the tattoo inks.  Hence, the commissioning of the JRC report to gather information about the tattooing and permanent make-up industry.  This report compiled data associated with the inks and makeup products in use including the ingredient analysis and adverse reaction data.  And, have provided subsequent recommendations about labeling and future regulation.

The Tattoo

Most have a general idea of how permanent tattoo is achieved, a colorant is injected into the skin using needles.  (Inset – Skin) A colorant can be either a dye or pigment.  In the case of a tattoo, the colorant is typically a pigment.  There is a critical difference between dyes and pigments.  Dyes require a physical or chemical interaction in order for the dye to be anchored into place, i.e. dyes react with the surface that is being colored.  Whereas, pigments do not require this type of interaction.  Tattoo inks are a solution comprised of a carrier and a pigment.  

When the JRC gathered data related to tattoos and inks, it was found that most tattoos, approximately 50 to 60% are black.  Other popular colors in descending order were determined to be red, blue, green, yellow and white.  According to the JRC Report, there are more than 100 colorants and 100 additives in current use to produce the tattoo inks.    It is the specific chemical identities of the colorants and additives that are the cause of concern as only about 30% of the pigments and dyes in use are approved for cosmetic use.  Most were developed for industrial applications like paints and coatings or textiles not for use in cosmetics or tattoo inks.  Thus, these colorants have not undergone any specific testing or risk evaluation that takes into account their injection into human skin.

Traditionally, the pigments used in tattoo inks were likely derived from mineral or geological sources.  Carbon (carbon black) or iron oxide can be used to produce a black ink.  Cinnabar, a mercury sulfide compound, has been used to produce red hues has been used since antiquity.  Cadmium compounds such as “cadmium red (CdSe)” or “cadmium yellow (CdS or CdZnS)” may be used to produce shades of red, orange, and yellow.  Green inks may contain chromium oxide or copper compounds.  Blues pigments derived from mineral sources may contain copper (II) carbonate (azurite), sodium aluminum silicate (lapis lazuli) or cobalt aluminum oxides (cobalt blue).  White is likely to contain titanium oxide or possibly lead carbonate.   However, over the last 20 years, the ink manufacturers have moved away from the primarily mineral based pigments to organic ones. 

The JRC Report indicates that over 80% of the colorant’s used today come from organic sources.  These organic pigments come with their own potential hazards. The long term fate, i.e. how these pigments degrade over time, is not well understood.  As approximately 60% of these organic pigments are azo pigments, there is the potential that the pigments can release carcinogenic aromatic amines as they breakdown, particularly when exposed to solar and ultraviolet radiation.  (See Azo Pigment Inset.)

In addition to the pigment, the inks are also comprised of the carrier and additives.  The carrier is the fluid that is used to transport the pigment to the application location.  In today’s inks the carrier solution may contain glycerin, water, isopropyl alcohol, and witch hazel.  The solution is also likely to contain a number of additives including surfactants, binding agents, fillers, and preservatives.  Many of these additives are employed to keep the pigments in a uniform suspension and to avoid microorganism growth in the product after opening.

The Potential Risks

The most common risk associated with a tattoo is that of an infection.  However, there are other potential known adverse reactions including allergic/hypersensitivity and auto-immune reactions, granulomas, and medical diagnostic and treatment interferences.  What is not known is the influence of the long term exposure to the pigment ingredients and the possible degradation products of the azo pigments.

The long term risks are associated with the quantity and type of pigment left in the skin producing the tattoo, i.e. the quantity of the ink injected and the overall coverage of the tattoo(s).  The JRC investigation determined that the inks used may contain up to 60% by weight of the pigment component.  But, what does that equate to under the skin?  The research showed that on average a tattoo contains 2.53 mg of colorant per square centimeter, or 400 cm2 (approximately 6”x10”) will contain 1 gram of pigment.  Thus, a little bit of pigment goes a long way, and not all pigments have potentially hazardous ingredients.  So, the individual risk associated with a tattoo is highly variable.

What Next?

Information is key to minimizing any risk. Distributors of quality inks now provide lists of ingredients used in their products as well as information about the conditions of use and other warnings.  This information can be obtained from the manufacturer or distributor of the ink.  While the FDA has yet to make recommendations, the JRC report is recommending consistent labeling and communication materials for tattoo inks.  At a minimum the packaging should contain, the name and address of the manufacturer, an expiration date, conditions of use and warnings, batch identification, list of ingredients and a guarantee of sterility.  It is also recommended that inks be packaged for single use.

While the most common reason for getting a tattoo may be associated with personal expression, there are others.  There are a number of iatrogenic tattoos used for medical applications.  For example, tattoos may be used to identify specific landmarks, such as the location of a biopsy site.   Therapeutic applications such as coloration of nipples in breast reconstruction.  Thus, there is a developing body of literature examining the chemistry of the tattoo as well as the ultimate fates of the pigments.  There is even research into the development of a potentially “erasable” tattoo utilizing polymers that can be degraded with a laser, should the person receiving the tattoo experience “tattoo regret” in the future.

Whether or not you have a tattoo, tattoos are a part of our culture. Tattoos have been around for more than 6000 years, and will be around for the foreseeable future.  It is tied to the chemistry of pigments as we humans seem to like to add a bit of color and self-expression to ourselves and surroundings.  And, it seems that we have a lot of potential avenues of investigation making even more interesting.

References for this Column

“The Chemistry of Tattoo Ink” 7/11/13 – Blog by acsundergrad.

“Tattoo Ink” What is that Stuff C&EN 11/12/2009

“Chemistry under your skin? Experiments with Tattoo Inks for Secondary Students”  M. Stuckey and I. Eiks. Journal of Chem. Ed. 2015, 92, 192-134

“Historic Mineral Pigments: Colorful Benchmarks of Ancient Civilizations” Mary Virgina Orna

“Safety of tattoos and permanent make-up” Final Report JRC Science for Policy Report

Subsequent Mentions and Other Information

Reference in the News & Observer

Reference in the Hartford Courant

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