From 1 September 2025, the EU banned TPO in cosmetics. But the same chemical — widely used as a photoinitiator in UV inks and 3D printing — remains on the market. For now.
Trimethylbenzoyl diphenylphosphine oxide (TPO) is little known outside laboratories. In the cosmetics sector, it is infamous — classified as a category 1B reprotoxic substance under EU chemical law. Regulation (EU) 2025/877 placed it on the prohibited list for cosmetics from the start of September, following adoption in May and Commission guidance in late August that confirmed the ban’s scope and timelines.
TPO is a synthetic organophosphorus compound developed in the late 1980s as a highly efficient photoinitiator. Produced mainly in China, India and Germany by fine-chemicals companies, it is supplied as a pale yellow crystalline powder or granules, usually packed in 20–25 kg drums for industrial use. When blended into UV-curable inks, coatings, adhesives or 3D printing resins (typically at 0.1–10% by weight), TPO absorbs UV light in the 350–420 nm range and splits into free radicals, initiating rapid polymerisation. Favoured for its high efficiency, ability to cure pigmented systems and for producing clear, colourless films, it became widely adopted across UV printing and additive manufacturing.
Yet while the cosmetics sector scrambles to replace it, Europe’s printing industry continues to rely on TPO. The compound is still addressed in the European Printing Ink Association’s suitability list for photoinitiators used in food-contact printing inks.
That contradiction worries experts. “Don’t you find it strange the media is silent?” wrote inkjet consultant Sergey Belokurov this week. He notes that even in cured inks, residual amounts of photoinitiators can migrate, especially in contact with fats, oils or solvents.
For those in the wide-format UV sector, the risk is practical. If Brussels extends restrictions beyond cosmetics, UV printer inks could face sudden reformulation, stranded stock, and customer delays, a pattern the industry has seen before when chemical classifications tighten.
There is also a human dimension. Workers in manufacturing plants, such as those filling bottles or operating UV printers, are exposed daily to uncured inks. Scientific literature shows that photoinitiator migration can occur from cured systems under certain conditions. Direct occupational data for TPO in print shops are limited, so the concern should be framed as potential rather than proven harm, but the question lingers whether TPO could become another decaBDE, once widely used, later banned outright after evidence of toxicity and persistence mounted.
With the cosmetics ban in place and pressure mounting on UV inks, suppliers are already exploring alternatives. Variants such as TPO-L (a liquid form with lower migration potential) and BAPO (bisacylphosphine oxide) are among the leading candidates. Yet both come with drawbacks: TPO-L is more expensive and less stable, while in-vitro studies suggest BAPO may be more cytotoxic than TPO. These are technical trade-offs, not regulatory endorsements, and they highlight how fragile the supply chain could become if restrictions expand.
And what of imports? Because inks containing TPO are not banned, UV inks with the substance can still be lawfully placed on the EU market. Customs inspections rarely verify the chemical composition, and enforcement often rests with overstretched national authorities. If restrictions are extended, importers and resellers holding stock could be left with warehouses of unsellable ink.
The cosmetics ban shows how fast regulation can move. For UV inkjet and 3D printing, the warning is written on the wall. Ignore it, and this “silent killer” may yet force an expensive and messy clean-up.
