The manufacturers likely added TPHP as a plasticizer, to render their polishes more flexible and durable. 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.
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. TPHP is also used in plastics manufacturing and as a fire retardant in foam furniture.
This study was conducted on 26 volunteers. Researchers tested the urine of 26 women volunteers before and after they applied nail polish. Technically, they looked for a chemical called Diphenyl phosphate (DPHP), which is created when the body metabolizes TPHP.
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. 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.
*‘It is very troubling that nail polish being marketed to women and teenage girls contains a suspected endocrine disruptor,”* said Johanna Congleton, Ph.D., MSPH, a senior scientist at EWG and co-author of the Duke-EWG study. “It is even more troubling to learn that their bodies absorb this chemical relatively quickly after they apply a coat of polish.’’
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.
A few tips to limit the risks of exposure:
• Read labels, and avoid products containing Triphenyl phosphate
• Use less nail polishes, or less often, especially if you’re a pregnant woman or a teenager
• Apply the colour in well-ventilated place, and do not inhale
• Avoid contact with cuticles
• Duke-EWG Study Finds Toxic Nail Polish Chemical In Women’s Bodies, October 19, 2015