It’s not surprising that many nail polishes contain potentially toxic chemicals. Now a study conducted by researchers at Duke University and EWG finds that at least one of those chemicals could be ending up in your body.
Triphenyl phosphate, or TPHP, a suspected endocrine-disrupting chemical, is commonly used to make plastics and as a fire retardant in foam furniture. And if you wear nail polish, it could be in your body too.
Researchers at Duke University tested the urine of 26 women who had recently painted their nails and found evidence of TPHP in every participant. Evidence of the chemical in the women’s urine increased sharply after they applied the nail polish.
TPHP is listed on the ingredient labels of a wide array of nail polishes now on the market. Out of more than 3,000 nail products in EWG’s Skin Deep database, half disclose the use of TPHP.*
Here’s where we found it:
Want to know more about TPHP and how you can avoid it? Click here to read the full report.
Nail polish chemical doubles as furniture fire retardant
A study co-authored by researchers at Duke University and EWG has detected evidence of a common nail polish chemical called triphenyl phosphate, or TPHP, in the bodies of every woman who volunteered to paint her nails for the study.
The results represent compelling evidence that TPHP, a suspected endocrine-disrupting chemical also used in plastics manufacturing and as a fire retardant in foam furniture, enters the human body via nail polish. These results are troubling because a growing body of scientific data from other studies indicates that TPHP causes endocrine disruption, meaning that it interferes with normal hormone functioning. In animal studies, it has caused reproductive and developmental irregularities. (Some studies use the acronym TPP for this chemical.)
TPHP is listed on the ingredient labels of a wide array of nail polishes now on the market. Fully 49 percent of more than 3,000 nail polishes and treatments compiled in EWG’s Skin Deep database disclose that they contain TPHP. Even worse, some polishes contain it but don’t disclose it.
The Duke-EWG study, published October 19, 2015 in Environment International, tested 10 nail polishes in all for TPHP and found it in eight of them.
Importantly, two of the eight polishes that tested positive for TPHP did not disclose its presence on product labels. 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. As well, the Duke team anticipated that some or all the manufacturers might update their product labels to disclose their TPHP use before the study could be published.
The manufacturers likely added TPHP as a plasticizer, to render their polishes more flexible and durable. The concentrations in the eight nail polishes with TPHP ranged from 0.49 percent to 1.68 percent by weight. Clear polishes generally contained more TPHP than colored polishes.
The study found that when women applied nail polish with TPHP directly to their nails, the levels of a biomarker of that chemical in their urine increased sharply. Technically, the researchers tested the women’s urine for a chemical called diphenyl phosphate or DPHP, which is created when the body metabolizes TPHP.
Most studies of TPHP involve investigations of its effects on cells and test animals. A few have associated the chemical with changes in the hormone and reproductive systems of humans. The most recent studies are striking—they suggest that TPHP interacts with a protein central to regulating the body’s metabolism and production of fat cells. Scientists are conducting more investigations to discover whether, in fact, TPHP contributes to weight gain and obesity.
Nail polish manufacturers may have turned to TPHP as a replacement plasticizer for dibutyl phthalate, or DBP, that was added to polish to improve flexibility. This chemical fell out of use in nail polish because highly publicized scientific studies showed that DBP and other phthalates are likely endocrine disruptors and toxic to the reproductive system.
Urine tests have found that Americans are extensively exposed to TPHP, probably because it is a common plasticizer and fire retardant often applied to foam cushioning in furniture. A recent biomonitoring study by Duke scientists who investigated TPHP exposure in adults found significantly higher levels of DPHP in women than in men who were tested in a separate study. These findings suggest that women may absorb more TPHP through personal care products, such as nail polish, that are marketed specifically to women.
Another biomonitoring study conducted last year by Duke and EWG researchers found DPHP, the metabolite of TPHP, in the urine of 95 percent of the adults and 100 percent of the children who participated (Butt 2014). A separate study by scientists from Duke University and the University of North Carolina found DPHP in more than 90 percent of samples collected from pregnant women (Hoffman 2014). An Australian study found DPHP in more than 95 percent of samples tested, and researchers in Asia found TPHP in 86 percent of breast milk samples from Japan, the Philippines and Vietnam (Kim 2014, Van den Eede 2015).
To investigate how TPHP from nail polish was absorbed into the body, study participants collected urine samples before and after they applied a polish that was about 1 percent TPHP by weight. When the participants wore gloves and applied polish to synthetic nails, their urinary levels of the metabolite DPHP did not change appreciably. However, when they applied the polish directly to their own nails, the levels of DPHP in their urine increased sharply.
Normally, most molecules do not permeate nails (Gupchup 1999). The researchers theorized that other polish ingredients such as solvents rendered nails more absorbent. They also suspected that the network of capillaries in the cuticle that surrounds the nail might play a role in carrying the chemical into the body.
Two to six hours after they painted their nails, 24 of the 26 volunteers in the study had slightly elevated levels of DPHP in their urine. Ten to 14 hours after polishing their nails, the DPHP levels in all 26 participants had risen by an average of nearly sevenfold, suggesting that more of the TPHP had entered their bodies and been metabolized into DPHP.
Four volunteers collected urine over 48 hours. For three of the four, their concentrations of DPHP peaked between 10 and 20 hours after painting their nails.
These results indicate that nail polish may be an important contributor to short-term TPHP exposure. For frequent users of nail polish, exposure to TPHP may be a long-term hazard.
TPHP: a new endocrine disruptor
Scientists knew little about the toxicity of TPHP until recently. But now there is growing evidence that the chemical could affect hormones, metabolism, reproduction and development.
In a 2014 study, rats exposed before and after birth to the flame retardant mixture Firemaster 550®, which contains up to 20 percent TPHP, grew obese. The females went through early puberty, an indication of irregularities in hormone signaling (Patisaul 2013).
In experiments with zebrafish, which scientists often use as a model to study endocrine disruption and development, researchers from Seoul National University in South Korea found that TPHP exposure altered sex hormone balance, which could harm reproductive performance. The scientists observed that TPHP changed the gene expression of certain receptors that could increase or decrease hormone activity; this change could interfere with endocrine and developmental signaling (Isales 2015, Liu 2012, Liu 2013a, Liu 2013b). Research on zebrafish showed that TPHP interfered with reproduction and could cause heart defects (Du 2015, Liu 2013b, McGee 2013).
In experiments on animal cells, scientists from the Hokkaido Institute of Public Health in Japan found that TPHP stimulated receptors for female sex hormones and antagonized the receptors for male sex hormones (Komija 2013). These fluctuations in the hormone system could alter reproductive function.
In another set of experiments, scientists from Boston University, the University of Cincinnati College of Medicine, Duke University and North Carolina State University found that Firemaster 550® activated the body’s “master regulator” of the process that governs the development of fat cells (Belcher 2014, Pillai 2014). The Duke/Boston team reported that Firemaster 550® stimulated fat cell maturation. Further experiments showed that TPHP diverted immature cells away from bone formation and toward fat development. Together, these results suggest TPHP could contribute to obesity.
TPHP has some structural similarity to tributyl tin—a substance suspected as a contributor to obesity because it can alter biological activity in a manner that leads to fat accumulation in animals exposed during early development.
A study led by a researcher at the University of Michigan School of Public Health found that adult men exposed to TPHP via house dust had lower sperm counts and produced more prolactin, a hormone that stimulates breast development and milk production in women (Meeker 2010). A second study led by the same team associated decreased semen quality with higher urinary concentrations of DPHP (Meeker 2013).
These and other recent studies raise serious questions about the possible impact of TPHP on hormones and fertility. Yet the chemical is hard to avoid. American manufacturers produced or imported more than 10 million pounds of TPHP in 2012 (EPA 2014). The biggest U.S. manufacturer of TPHP is a single chemical company, ICL-IP, which is a leader in the American fire retardant chemical market. The same company also makes plasticizers for a variety of industrial uses. EWG scientists could not determine how much TPHP from any source winds up in nail polish.
Chemical policy reform is urgently needed to protect Americans from endocrine disruptors
Beginning in 2004, in response to pressure from EWG and other environmental health advocates, U.S. manufacturers voluntarily stopped making and using a class of fire retardant chemicals called polybrominated diphenyl ethers or PBDEs. PBDEs are endocrine disruptors that persist in the environment and in the food chain. But instead of banishing toxic fire retardants from consumer items manufacturers continued to use other chemicals, including TPHP, and produced new mixtures with little to no safety information.
Under the federal law, chemical manufacturers are not required to provide information about the safety of their products and the effects on humans, animals and the environment before they market them. Because of this gaping loophole, manufacturers constantly swap out one toxic chemical for another that may be less controversial but is potentially just as hazardous.
The federal law has failed to control human exposure to toxic chemicals such as fire retardants. Its ambiguous, fatally flawed safety standard has contributed to the widespread use of chemicals whose safety has not been established.
EWG is working to reform federal chemical and cosmetics regulation by establishing a stronger safety standard that would require chemical makers to prove that their products posed “reasonable certainty of no harm.” Such a standard would put a rigorous, health-protective burden of proof on the manufacturer to show its products were safe before they came to market.
- If you use nail polish, read the label. If the label says triphenyl phosphate, TPHP, dibutyl phthalate or DBP, don’t buy it. Use EWG’s Skin Deep database to find products without these ingredients.
- Nail polish marketed especially to children may be formulated differently from adult polish. But parents should check labels. Youngsters should not use adult nail polish containing triphenyl phosphate or its synonyms – TPHP and TPP.
- If you are shopping for new furniture, check with the store or manufacturer to find out if your prospective purchases contain fire retardants. TPHP isn’t the only fire retardant that may cause health problems. Choose products free of fire retardants.
- Americans need chemical policy reform. Congress should enact legislation to update federal chemical and cosmetics law with a safety standard that requires a chemical to present “reasonable certainty of no harm.”
Dr. Heather Stapleton, study Principal Investigator, Associate Professor of Environmental Sciences and Policy in the Nicholas School of the Environment, Duke University.
Emma Mendelsohn, study lead author, Nicholas School of the Environment, Duke University.
*The product ratings, images, conclusions, recommendations, and findings that appear on EWG’s web, database, and mobile application properties, or in e-mail messages, reflect EWG’s research at the time of publication. Please be advised that this information frequently relies on data obtained from many sources, and accordingly, EWG cannot guarantee the accuracy of the information provided or any analysis based thereon. Moreover, in light of evolving regulatory and market conditions, subsequent product reformulations, and other factors, this information may no longer be current. Please read our full disclaimer here.
**On October 20th 2015, Butter London informed EWG that it had removed triphenyl phosphate (TPHP) from its products last year. However, EWG was still able to find nail polish products containing triphenyl phosphate on store shelves in September 2015. If you would like to avoid triphenyl phosphate, please check the label on Butter London products and purchase ones with the newer formulation that do not contain this ingredient.