For the first time, science has confirmed that nanoparticles from your tattoos will end up in your lymph nodes.
Humans have been permanently decorating our skin with ink for at least 5,000 years, but we still don't really know what effect, if any, they have on our bodies.
Now, for the first time, scientists have found evidence that both pigments and impurities from the tattoo ink can travel around your body as nanoparticles.
How tattoos work is actually pretty brilliant. The ink is precisely deposited via a needle below both the dermis and epidermis, where, too big for your immune system to break down, the ink particles will remain permanently.
Laser removal breaks these particles down into small enough pieces so your body can dispose of them.
But, while most of the ink stays put, a minute amount of it does end up getting removed by the immune system. And, according to researchers at the European Synchrotron, that could be a problem, since we don't know what it could do to our body.
"When someone wants to get a tattoo, they are often very careful in choosing a parlour where they use sterile needles that haven't been used previously," said researcher Hiram Castillo.
"No one checks the chemical composition of the colours, but our study shows that maybe they should."
The composition of tattoo pigments could have an unknown effect on the body. They could, for instance, contain impurities. They contain preservatives and contaminants such as cobalt, chromium, manganese and nickel. Allergic and other reactions to tattoo inks are not uncommon.
One very common ingredient is titanium dioxide, used for white ink. This is also used to lighten other coloured pigments. The researchers tracked several of these types of tattoo nanoparticles through the body using X-ray microscopy and X-ray nanoprobe beamlines.
"We already knew that pigments from tattoos would travel to the lymph nodes because of visual evidence: the lymph nodes become tinted with the colour of the tattoo. It is the response of the body to clean the site of entrance of the tattoo," said one of the research team, Bernhard Hesse.
"What we didn't know is that they do it in a nano form, which implies that they may not have the same behaviour as the particles at a micro level. And that is the problem: we don't know how nanoparticles react."
The team tracked micro- and nanoparticles in the skin and lymph nodes. They found microparticles in the skin, but only nanoparticles made it into the lymph nodes, both of organic pigments and titanium dioxide.
They also used infrared spectroscopy to determine that there were structural changes in the tissue surrounding these particles.
Tattoos aren't all bad, though. Previous research showed that getting multiple tattoos strengthens your immune system by working it harder, like taking it to an immune system gym.
But the research could help determine not just the effects of tattoos, but substances such as cosmetics and sunscreens, which also contain titanium dioxide.
"In future experiments we will also look into the pigment and heavy metal burden of other, more distant internal organs and tissues in order to track any possible biodistribution of tattoo ink ingredients throughout the body," the researchers wrote in their paper.
"The outcome of these investigations not only will be helpful in the assessment of the health risks associated with tattooing but also in the judgment of other exposures such as ... the entrance of titanium dioxide nanoparticles present in cosmetics at the site of damaged skin."
The research has been published in the journal Scientific Reports.
In recent years, tattooing has become more and more popular, especially among young people. Why? Fun, a statement of personal identity, and peer pressure are all potential motivations. However, the decision to get a tattoo should not rely simply on social or aesthetic reasons. Other considerations should include health concerns about the ingredients of tattoo inks, the risks of unclean tattooing practices, potential costs for tattoo removal, and the minimum age for getting a tattoo without parental permission.
Behind all the practices of tattooing is a lot of science: from the biochemical effects of tattoo inks to the chemistry of pigments. To make science more relevant to the lives of our students, we have developed a lesson plan for lower-secondary schools that uses hands-on activities related to tattoos (Stuckey et al, 2013; Stuckey & Eilks, 2014; Stuckey & Eilks, 2015). Here we present four of the activities to investigate the contents and thermal stability of tattoo inks.
Detection of metal ions in tattoo inks
Some of the components of tattoo inks, such as heavy metal compounds, can be harmful to health. A simple flame test can be used to indicate the presence of different metals in tattoo inks.
Each group of students will require:
- Wooden splints
- A Bunsen burner
- Crucible tongs
- A selection of tattoo inks (colours and brands)
- Dip the end of a splint into a small drop of tattoo ink.
- Using the crucible tongs, hold the splint in the flame of the Bunsen burner.
- Record the colour of the flame. The colour corresponds to particular metal atoms in the ink. For example, blue tattoo inks regularly produce a green flame due to the presence of copper atoms.
- Cut off the used end of the splint or use a new one to repeat the experiment with a different ink sample.
- Suggest which metals are contained in which inks.
Discuss with your students whether there are allergy or safety concerns about these metals. For example, red inks containing chromium salts can often cause allergic reactions.
Identifying the compounds in the inks
While there is a European regulatory framework for tattoo chemicals, not all countries have signed up to it. In some countries, such as Germany, tattoo inks must be licenced and comprehensibly labelled. Not all brands of tattoo ink provide this level of detail, however; although they are not licenced for use in Germany, they can be bought cheaply over the Internet. If your tattoo inks are comprehensibly labelled, your students can investigate their contents in more detail.
- Referring to the labels, list the colouring agents in the inks, including the ‘CI’ number.
- Consult Colour Indexw1, an online reference database of dyes and pigments, to determine the identity of the chemicals. For example, CI 74160, which is found in some blue tattoo inks, is the pigment phthalocyanine blue, a copper complex.
- How do these results compare to the results of the flame tests in the previous activity?
- What can you find out about these pigments? For example, are there any health concerns? What other purposes are the pigments used for? Some tattoo pigments, for instance, are also found in car finishes.
If your tattoo inks are not comprehensibly labelled, why might this be a problem?
Stability of tattoo inks
Students can also investigate the thermal stability of different tattoo inks. It is important that the inks are thermally stable to avoid changes once they are tattooed into the skin.
- Porcelain crucibles with lids
- Crucible tongs
- A tripod
- Metal gauze
- A Bunsen burner
- A selection of tattoo inks
- Put a drop of one ink into a porcelain crucible.
- Put a lid over the crucible and place it on the gauze above the Bunsen burner.
- Heat the crucible for 30 seconds, then remove from the heat using the tongs.
- Remove the lid and record any changes in the appearance of the ink drop.
- Repeat for the other inks.
Many tattoo inks are quite heat resistant but others rapidly decompose into a muddy brown mass. When tested by our students, some of the cheap inks bought via the Internet decomposed rapidly. There are also reports of some inks losing their colour when exposed to sunlight.
Investigating the impact on enzyme activity
The potential health impact of tattoo inks can be investigated by looking at their effects on enzyme activity.
- Petri dishes
- Aqueous hydrogen peroxide (3%)
- Raw potatoes
- A selection of tattoo inks, diluted with water to a thin, water-like, consistency.
- Carefully cut a potato into pieces around 1cm3.
- Place one piece of potato into one of the diluted tattoo inks and leave for 10–15 minutes.
- Remove the piece of potato and place it in a Petri dish of hydrogen peroxide solution.
- Observe what happens.
- Repeat for the other tattoo inks.
- Place one piece of potato that has not been treated with ink in the Petri dish full of hydrogen peroxide solution.
Potatoes contain the enzyme catalase, which catalyses the decomposition of hydrogen peroxide into water and oxygen. The piece of potato that was not treated with tattoo ink will react strongly with the hydrogen peroxide solution, causing effervescence as oxygen is generated. The reactions of the treated pieces of potato will vary, as many of the metal ions used in tattoo inks (such as copper) inhibit the action of catalase.
- How might the observed effects on the potato pieces translate to the human body? Are the effects cause for concern?
- German-language instructions for carrying out these and other activities related to tattoos can be downloaded free of charge from the Profiles Bremen website.
- Full teaching and learning materials for the activities (in German) can be found in:
- Stuckey M, Eilks I (2014) Tätowierungen - Chemie, die unter die Haut geht. RAABits Chemie Sekundarstufe I, February: 1-30
Marc Stuckey is a teacher at the IGS Wilhelmshaven (comprehensive school), Germany, and a former student in Ingo Eilks’ chemistry education research group based at the University of Bremen, Germany. Together they developed this activity and are grateful for the generous support of the Profiles project funded by the European Union under the 7th Framework Programme for Research Funding, Science in Society, under grant agreement number 266589.
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