articleThe Brief The European Union is banning certain gel nail polish brands that contain TPO, or trimethylbenzoyl diphenylphosphine oxide. TPO is the chemical compound that makes gel polish harden under UV lights and gives it a glass-like finish. The European Union has banned a chemical used in many popular gel nail polish brands, citing studies that link it to fertility issues. The studies that prompted the EU to ban certain gel polishes that contain TPO often focused on animal subjects, not humans. UV/LED lamps safetyThe backstory:The lamps help to cure gel manicures and dry polish.