Scientists explore the chemistry of tattoo inks amid growing safety concerns

Larger / Scientists have found that tattoo ink ingredient labels are often inaccurate and some inks contain nano-scale particles that can damage human cells.

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Scientists at Binghamton University (State University of New York) have analyzed nearly 100 different tattoo inks and found that manufacturers’ ingredient labels (when used) are often inaccurate and that many inks contain tiny nano-scale particles that can be harmful to human cells. . They presented their findings at this week’s meeting of the American Chemical Society (ACS) in Chicago.

According to principal investigator John Swierk, a chemist in Binghamton, the project first began when his group became interested in tattoos as tools for medical diagnosis. This shifted to an interest in laser tattoo removal, specifically how laser light causes tattoos to fade. “We realized we didn’t understand much about the interaction between light and tattoos,” Swierk said during a press conference at the ACS meeting. “My group studies how light can drive chemical reactions, so it was a natural fit.”

This meant learning more about the chemistry of tattoo inks, which is also not well understood. One reason for this significant gap in scientific understanding is that, at least in the US, tattoo ink manufacturers are not required to disclose ingredients, and even when they do, there is no real oversight of whether those disclosures are accurate, Swierk said.

Typical tattoo ink contains one or more pigments (which give the ink its color) inside a “carrier package” to help deliver the pigments to the skin. The pigments are the same as those used in paints and textiles. They can be either small pieces of solids or discrete molecules, such as titanium dioxide or iron oxide (for white or rust-brown colors, respectively). As for the retainer packs, most ink manufacturers use grain or rubbing alcohol, sometimes with a little witch hazel added to the mix to help the skin heal after the tattooing process. There may also be other additives to adjust the viscosity and keep the pigment particles suspended in the carrier package.

The European Union has recently cracked down on blue and green pigments used in tattoo inks.
Larger / The European Union has recently cracked down on blue and green pigments used in tattoo inks.

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First, the team interviewed several tattoo artists and found that while the artists had their favorite brands, they knew very little about the chemical composition of their favorite inks. Swierk’s lab then used various methods to analyze a wide range of commonly used tattoo inks, including Raman spectroscopy, nuclear magnetic resonance spectroscopy, and electron microscopy. This enabled them to identify specific pigments and other ingredients in different paints.

They found that many ingredients did not appear on manufacturers’ labels, such as a paint that contained ethanol even though it was not listed on the label. And 23 of the dyes analyzed so far show evidence of an azo-containing dye. Such pigments are usually inert, but exposure to bacteria or ultraviolet light can cause them to degrade into a potentially cancer-causing nitrogen-based compound.

Additionally, says Swierk, “Often the particle sizes used in tattoo inks are very small—less than 100 nanometers in diameter. When you get to that size regime, you start to have concerns about nanoparticles penetrating cells, getting into the core and doing damage, possibly causing cancer.” About half of the 18 paints analyzed by electron microscopy had particles in this worrisome size range.

Bottles of colored ink mixed together in a box in a tattoo parlor in Berlin.
Larger / Bottles of colored ink mixed together in a box in a tattoo parlor in Berlin.

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The European Commission has recently begun cracking down on harmful chemicals in tattoo ink, including two widely used blue and green pigments (Pigment Blue 15 and Pigment Green 7), claiming they are often of low purity and can contain dangerous substances. “Anyone getting a tattoo in the US with blue or green tattoo inks should assume that those pesky pigments will be involved,” Swierk said. “Most tattoo manufacturers are discontinuing the sale of blue and green inks in Europe [in response to the regulatory crackdown]not necessarily changing pigments, because there’s no obvious replacement at this point.”

However, he added that while the EU’s scientific data is worrying, it is not yet conclusive on the general safety of pigments alone. “Those particular pigments have been used in tattoos for a very long time,” Swierk said. “As with everything involving tattoos, it is up to consumers to make a decision about their particular comfort level and then proceed accordingly.”

That’s why Swierk and his team have created a new website, What’s in My Ink? Their research will ultimately constitute the first comprehensive study of tattoo inks on the US market, according to Swierk. There is currently only rudimentary data from previous peer-reviewed studies available on the site, but once his team completes its analysis of commercial tattoo inks and the resulting data goes through the peer-review process, the site will serve as a valuable consumer resource for information about the composition of tattoo inks.

The science and chemistry at play on our skin reacts with tattoo ink.

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