If you regularly apply nail polish, you may want to check the label.

And depending on what you find, you might want to switch nail polish brands.

A study from the Environmental Working Group (EWG) and Duke University shows that wearing nail polish for 10-14 hours could have some unexpected (and undesirable) side effects.

The study looked at 26 volunteers, who applied nail polish, then went about their daily business. About 10 to 14 hours later, researchers tested the subjects and found triphenyl phosphate (TPHB) in every single participant. What’s more, a release accompanying the study notes that “evidence of the chemical in the women’s urine increased sharply after they applied the nail polish.”

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“Importantly, two of the eight polishes that tested positive for TPHP did not disclose its presence on product labels,” the press release states. “The Duke researchers decided not to make public the names of those two polishes or the six others that contained TPHP and disclosed it because the lab tested only 10 samples, not the manufacturers’ entire nail product lines.”

The study’s authors also anticipated that some manufacturers might change their labels to report the presence of TPHB prior to the study’s release.

So, why is that potentially a big deal?

TPHB is a plasticizer, used to make products more flexible. In nail polish, it may be used to prevent premature cracking.

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Several studies show that TPHB can create changes in the endocrine systems of animals and in the hormone and reproductive systems of humans. Some scientists worry that the chemical might also increase the risk of certain illnesses.

What’s more, some studies show a correlation between TPHB and weight gain. It may affect body metabolism, raising the risk of obesity.

Nail polish manufacturers have only recently started using TPHB, often as a replacement for another potentially dangerous chemical, dibutyl phthalate (DBP). DPB was linked to reproductive system issues, and manufacturers tend to avoid it, along with other chemicals in the phthalate class.

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The press release also notes that TPHB is also used in fire retardant foam cushioning in furniture.

Normally, the chemicals in nail polish are unable to get through fingernails to enter the body. Researchers believe that some of the other ingredients in polishes may weaken the nails, however, allowing potentially harmful chemicals like TPHB to permeate the surface.

In total, about 1,500 or the 3,000 products in EWG’s database use the chemical.Of course, this study uses an extremely small selection of participants, and further research will be necessary to determine whether the chemicals really pose a serious health threat.

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“These results indicate that nail polish may be an important contributor to short-term TPHP exposure,” the study reads. “For frequent users of nail polish, exposure to TPHP may be a long-term hazard.”

Still, it’s alarming news for anyone who uses polish—or, at least, anyone who uses one of the polishes that include the ingredient. EWG has published a list of the brands and manufacturers that use TPHP.

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You can view the organization’s full list here.