Nail Polish Source of Exposure to Toxic Chemical.

A research team that includes a School of Public Health environmental health professor has found evidence that a suspected endocrine-disrupting chemical widely used in nail polishes seeps into the bodies of women when they paint their nails.

The study, by authors from Duke University, the Environmental Working Group (EWG), and SPH Professor Thomas Webster, found that all 26 female study participants had a metabolite of triphenyl phosphate, or TPHP, in their bodies just 10 to 14 hours after painting their nails. Their levels of diphenyl phosphate, which forms when the body metabolizes TPHP, increased nearly sevenfold.

TPHP is primarily used as a flame retardant or plasticizer and is listed as an ingredient in about half of nail polishes. Scientists are increasingly concerned about TPHP because animal studies indicate it is an endocrine disruptor that may cause reproductive, developmental, and other problems.

The research, published in the journal Environment International, measured TPHP in 10 different nail polish samples purchased from department stores and pharmacies in 2013–2014. Concentrations of up to 1.68 percent TPHP by weight were detected in eight samples, including two that did not list TPHP as an ingredient.

Participants provided urine samples before and after applying one brand of polish, and levels of diphenyl phosphate (DPHP) were measured. Urinary DPHP was significantly diminished when wearing gloves, suggesting that the primary exposure route is dermal.

The results “indicate that nail polish may be a significant source of short-term TPHP exposure and a source of chronic exposure for frequent users or those occupationally exposed,” the researchers said.

They said additional research is needed to determine exposure routes, and to better understand variability in DPHP excretion following exposure.

The study was led by Heather Stapleton of Duke University.

—Lisa Chedekel