TPO is specifically a type of photoinitiator that absorbs UV light and triggers the hardening process of gel-based nail products. It is known for providing a fast cure time and can be used in both UV and LED lamp systems commonly found in nail salons. It is currently considered "safe" to use in concentrations of up to 5% in cosmetics for use by professionals. It is commonly also used in the dental industrt so important to note that it is not specifically the nail industry being targeted.
TPO is being banned in cosmetic products in the EU from September 2025, but why?
Lets first look at TPO...
TPO is currently so widely used as its such an effective photo initiator. TPO (Trimethylbenzoyl-diphenylphosphine oxide) is considered more effective as a photoinitiator in certain applications, for several reasons:
- Broad Absorption Spectrum:TPO has a broad absorption spectrum in the ultraviolet (UV) region, particularly in the near-UV range (around 350-400 nm). This allows it to be activated by a wider range of UV light sources, including LED UV lights, which are increasingly used in curing processes.
- High Reactivity:TPO is highly reactive, meaning it can efficiently initiate polymerization when exposed to UV light, this leads to faster curing times and more complete polymerization,
- Low Yellowing:Unlike some other photoinitiators, TPO tends to produce less yellowing in cured products.
- Compatibility with Various Monomers:TPO is compatible with a wide range of monomers and oligomers used in UV-curable formulations. This makes it a flexible option for formulators who need to create products with specific performance characteristics.
- Effective in Thick Layers:TPO is effective in curing thicker layers of material because it can penetrate deeper into the material due to its absorption characteristics.
- Reduced Oxygen Inhibition:TPO is less susceptible to oxygen inhibition compared to other photoinitiators, which helps ensure a complete and even cure, even in the presence of air.
If we take out TPO what will happen? Going forward with the removal of TPO from nail formulations its important to understand that there may be a difference in the ways your gels perform. As an example a common replacement of TPO is TPO-L, this tends to polymerise faster leading to more heat being generated in a shorter period of time, this heat may be felt by clients. Unfortunately there are no other photo initiators that are quite as effective as TPO which means that there could be noticeable differences in formulas in the nail industry in the future in terms of colour and the heat felt and or expelled during the curing process.
Why is it being banned? TPO is being banned following a study performed on rats in Germany is 2020 that concluded that the exposure to TPO had caused reproductive toxicity. The rats in the study were fed 600 mg/kg of body weight every day for 10 days.
To put this into context, if you took a rat of 200g this would equate to 0.12g of TPO being ingested every day for 10 days. To compare this to nail products, an entire 25g jar of Dura Gel contains 0.07g of TPO. For a human to be exposed to the same level of toxicity, a 60kg person would need to ingest 36,000mg (36g) everyday for 10 days, this would be the equivalent of 514 jars of Dura gel eaten every day for 10 days.
What are Nail Order doing about TPO in their formulas? Here at Nail Order, we have been aware of the upcoming ban on TPO for some time. We only have a couple of gels that contain TPO and at very low percentages (0.99% and 0.29%, and the good news is that these gels have already been reformulated to be free from TPO and they will be rolled out in the coming months.
Should you be worried about using a gel with TPO in it? Whilst its always important to be aware of concerns regarding the chemicals that you are using, its also important to be aware of the facts surrounding these concerns. As demonstrated above, a human would need to ingest a very large quantity of gel to be exposed to the same level of toxicity as the rats that showed reproductive problems. So, as with everything its about eduction, using professional use products and using them in a safe manner.