Everybody knows there are dangerous-sounding chemicals in nail polish, but many of us think our limited contact with wet polish is too minimal to cause much risk. After all, we're not drinking it!
But new research may chip away at your worry-free tradition of weekly mani-pedis: A study led by Duke University and the public health advocacy organization Environmental Working Group suggests that we absorb at least one potentially hormone-disrupting chemical every time we get a polish. While the impact of this chemical on our health is still unclear, the fact that our body can absorb chemicals through nail polish is cause for concern.
The chemical in question is triphenyl phosphate, or TPP. Companies add it to products to make them less flammable, although in nail polish it's used to make the product stick more strongly to the nail.
TPP is listed as an ingredient in about 49 percent of the 3,000 nail polishes and treatments in EWG’s database, but the group suspects there may be more companies who use the chemical but don’t disclose it. TPP is also commonly used in many consumer goods, like foam seating, bedding products, and electronic products, which might be why researchers have found the chemical in the majority of participants in studies on pregnant women and international samples of breast milk.
Companies have been using TPP in consumer products since it was first patented in 1910. A definitive report from the Organization for Economic Cooperation and Development, an international policy forum for democratic market-based governments, found in 2002 that because TPP causes almost no irritation to the skin and barely any irritation to the eyes, the chemical is of "low priority for further work" when it comes to human health. While people are advised to seek medical help immediately if accidentally ingested, according to the National Institute for Occupational Safety and Health, it's generally regarded as safe to use in products.
However, worrying new correlational studies about the chemical's potential to disrupt hormones in people and animals are causing scientists and activists to take a fresh look. In particular, the Duke study raises questions about the potential effects of low-level TPP absorption over time.
Urine analysis finds TPP metabolites
To see whether TPP enters the body through paint on nails or particles in the air, the researchers divided study participants into two groups: the first would get a normal manicure in which nail polish was painted directly onto their nails, while the second group wore gloves and got nail polish applied on fake nails. The polish used in these experiments contained about one percent TPP by weight.
Then they tested participants' urine for levels of diphenyl phosphate, or DPHP, a chemical created when the body metabolizes TPP. They compared the results to urine samples participants had submitted before the experiment and found that while DPHP levels didn’t change very much in the participants who used gloves and fake nails, levels of DPHP increased sharply in the women who had received nail polish directly on their nails.
About ten to 14 hours after getting their nails painted, the participants had DPHP levels that were on average seven times higher than they were before the experiment. About 10 to 20 hours later, the chemical seemed to peak and decrease, indicating that the nail polish could be a source of short-term TPP exposure. The study did not name the nail polishes used, in part because they only had ten sample polishes and also because they weren’t sure if TPP content was uniform among brands.
Should you be worried?
Not yet. Richard Sachleben, an expert spokesman for the American Chemical Society and an organic chemist with more than 30 years of experience, points out that research to date on TPP suggests that the chemical is a "low priority" for further research because both acute and chronic toxicity is low in humans and the outcome amounts to mild irritation.
Sachleben praised the Duke and EWG study as sound science, but pointed out that the research as it's designed doesn't establish whether elevated levels of TPP actually hurt human beings. The most disturbing thing about the chemical is its potential to interfere with hormones, but these studies have only been conducted in animals or show correlation, not causation, in human beings.
A July 2015 study found that mice treated with TPP for about a month had shrunken testes, while a June 2015 study found that TPP was among a class of flame retardants that can alter sex hormones in zebra fish. And a study in human beings found that higher levels of TPP in the home (most likely found in furniture foam) was linked to a lower sperm concentration and an increase in prolactin, a hormone associated with sexual problems in men.
An occupational hazard
While consumers have less cause for concern, the people who actually do nails for a living, day in and day out, are awash in these chemicals and bear the brunt of their harmful effects in the body.
Thu Quach, a research scientist at the Cancer Prevention Institute of California and research directer at Asian Health Services in California's Bay Area, finds Duke and EWG’s findings more alarming.
She’s spent the past 10 years researching the health effects of nail polish chemicals, and her organizations are core members of a coalition called the California Healthy Nail Salon Collaborative that aims to make nail salons safer for workers.
Part of their campaign in the past has focused on removing the “toxic trio” of formaldehyde, toluene and dibutyl phthalate from nail polish formulas because of their harmful effects on nail techs. But Quach suspects that as more companies remove the chemicals from nail polish, they’re replacing them with chemicals that may be just as harmful, or have the potential for harm — like TPP. Dibutyl phthalate, for instance, is also a hormone disruptor, and Quach has observed that as this chemical is removed from nail polish, other chemicals are increasing in volume to replace it.
"There have been concerns that as the manufacturers are phasing out the dibutyl phthalates, they’re replacing it more with triphenyl phosphates," said Quach.
She added that while TPP has always been in nail polishes in smaller doses, its amount is now increasing in association with the decreasing use of dibutyl phthalate. And because nail techs are exposed to these polishes all day through particles in the air, the potential risks are even greater for them than they are for consumers. To be clear, however, the Duke research identified chemical uptake via nail polish, not particles in the air, as the problem.
Fighting for regulation
Instead of activists and researchers playing wack-a-mole with chemicals, campaigning against one toxic substance only for it to be replaced by another, Quach thinks that voters should push the government to regulate cosmetic products comprehensively, so that there are no more endocrine disruptors or toxic chemicals in them.
Nail polishes and other nail products are regulated by the Food and Drug Administration, but not at the pre-market stage. That means the FDA does not have to approve formulations before they hit store shelves. Instead, the FDA can enforce the law against products or companies that violate it. The agency acknowledges that there are harmful ingredients in nail polish, but says they are safe when used as directed (i.e. painted, not ingested). But Duke and EWG point out that while human nails are generally not absorbent, certain nail solvents or treatments used before nail polish application may wear down nail material and make it more permeable, allowing the body to absorb the chemicals.
"It was great that the study highlights another endocrine disruptor that can be found in consumer products, but again it really points to the gap in our regulatory system that says we have to go after chemical by chemical," said Quach. "We’re really trying to get the government to be more accountable in getting these manufacturers to report what’s in there, rather than wait for studies to come out."