September always brings with it a let’s–get-stuff-done energy, and apparently, the EU has taken note. Starting September 1st, the EU banned all nail polishes that contain the ingredient TPO from being sold or used by technicians and salons. They listed the ingredient as a CMR (carcinogen, mutagen, and reprotoxic), meaning it could promote cancer, cause permanent change to genetic material, or lead to reproductive and fetal issues. The UK also looks set to follow suit before long. For all those wondering, here’s what the change means for your biweekly manicure stateside.

What is TPO?

“TPO, or trimethylbenzoyl diphenylphosphine oxide, is a key ingredient found in many gel products, especially top coats,” celebrity manicurist Michelle Class explains. TPO is not present in normal, air-dry nail polishes. “It’s the photoinitiator that reacts to UV or LED light, transforming soft, uncured gel into the hard, glossy finish we love.”

TPO is expected to also be banned in the UK from late 2026 or early 2027, due to ongoing concerns around it potentially causing fertility and reproductive issues. Research performed on rats found that when TPO was ingested, reproductive difficulties and negative effects on the endocrine (hormonal) systems followed. “Because of these issues, the EU regulatory body decided to ban TPO,” Claire Aggarwal, CEO of UK-only brand Bio Sculpture, says. In fact, the EU has gone so far as to label TPO as a “reprotoxic substance,” meaning it’s been proven to negatively affect the ability to reproduce and could harm the development of any offspring.

Is TPO dangerous for humans?

“We have to be aware, though, that these issues arose only when TPO was ingested, and when it’s used on nails, it isn’t ingested,” Aggarwal points out. “There are still many products on the market – and from big brands – that are not TPO free. So, if you have any issues with your endocrine system or, perhaps, are trying to get pregnant, choosing a brand that is TPO-free could be advisable.”

With all this concern, why has TPO been used for so long? Largely because of how effective it is at creating a hard, chip-resistant finish and, crucially, because of its low “yellowing” rate. Yellowing can happen with some topcoats when they’re cured, giving nails an unwanted, slightly off-color tint. Plus, the risk posed by polishes containing TPO is low.