PITTSBURGH —

That glossy gel manicure might look flawless, but it’s what’s inside some gel polish that is causing concern and changes across the European Union.

“TPO is trimethyl benzoyl diphenyl phosphine oxide," said Dr. Charles Mount, dermatologist and associate director of the AHN Cancer Institute skin cancer center. "It's what's known as a photoinitiator." Advertisement

That means TPO reacts with UV or LED light, transforming sticky, gooey gel into a hard, shiny, durable nail finish.

The EU just banned TPO after animal studies linked it to fertility problems in rats and potential carcinogenic effects.

"They essentially fed the chemical to rats in those animal studies, and they saw that there was decreased fertility rates. Specifically, there was decreased sperm production and te

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