Dirty needles may be the chief health concern with tattoos, but preliminary research suggests the inks used to make the body art may harbor potentially toxic heavy metals.

In an analysis of 17 tattoo inks from five manufacturers, researchers found evidence of a number of different metals, such as nickel and copper, in the products. It’s unclear how much metal may be in the different inks - or whether there is any health risk.

Still, the study authors say the findings highlight the lack of oversight of tattoo ink manufacturing.

The U.S. Food and Drug Administration (FDA), which approves the color additives used in foods, cosmetics and drugs, does not regulate the inks used for tattooing, and no color additive has ever been approved for injection into the skin.

“A lot of people are surprised by that,” said Leslie Wagner, a chemistry student at Northern Arizona University in Flagstaff and a co-author on the new study.

Many tattoo enthusiasts may assume that an ink that’s injected into the skin has been approved by regulators to meet certain standards, she noted in an interview with AMN Health.

However, it is not even clear what goes into a given tattoo pigment. Because the inks are not sold directly to consumers, manufacturers are not required to list the components on the product label, according to the FDA.

And no previous scientific studies have attempted to describe the composition of the inks, Wagner said.

In their research, Wagner and co-author Haley Finley-Jones have so far found that tattoo ink compositions vary from manufacturer to manufacturer, and from color to color. Moreover, Wagner said, “we’ve found a lot of indications of metals.”

She and Finley-Jones presented the preliminary findings Sunday in San Diego, at the 229th national meeting of the American Chemical Society.

Tests are still underway to confirm the identities of all the metals in the tattoo inks, as well as the concentrations present. The health effects, if any, will require further research, according to Wagner.

However, she pointed to reports of certain tattoo complications for which the causes are currently unknown. People have, for example, been burned in tattooed skin areas during MRI scans, while others have developed allergic reactions to tattoo inks.

Whether the presence of metals in the inks has anything to do with these problems is not yet clear, according to Wagner.

“We’re not trying to make any big claims that this is harmful,” she said.

Even if tattoo ink components turn out to have no ill health effects, knowing their make-up could at least make things for easier for those who have second thoughts about their body art, Wagner noted.

Right now, tattoo removal is a fairly difficult process - often requiring several laser treatments to lighten the tattoo, with varying aesthetic results. It’s possible, Wagner said, that knowing the exact composition of tattoo pigments will help refine tattoo removal techniques.