Introduction
Nitrosamines are a carcinogenic chemical compound family, prohibited as ingredients in formulation but which can appears during ageing process of cosmetic products. Hindering this phenomenon is one of the actual major concerns of cosmetic formulators to guarantee the safety and cleanliness of cosmetic products. If all the tracks explored for nitrosamines limitation in nail polishes have been rather deceiving, the 3 years collaboration between ILCosmetics Group, European leader of nail polish, and CSTA, a consulting company, bring a convincing solution
Maltol is a tiny natural anti-oxidiser from the pyranones family but its efficiency against nitrosamines in nail polishes had never been explored. Being soluble in nail polish matrix, we investigated its inhibition and degradation of nitrosamines potential in such cosmetic product. Using it in nail polishes stopped the formation of nitrosamines and also degraded the ones brought by raw materials!
Nitrosamines and nail polish
Stable nitrosamines come from the combination of molecules not used directly in a nail polish formulation, but which can appear during the ageing process.
Moreover, providers or manufacturers do not systematically explore the presence of nitrosamines in raw materials used in nail polish formulation since this kind of pollution is not necessarily expected. However, nitrosamines traces can easily come from accidental pollution or goods ageing. Using such untested raw material can be one of the sources of nitrosamines in cosmetic products.
Anyway, if nitrosamines are observed in nail polishes, it always is as traces (a hundred of ppb), no matter that they come from a raw material pollution or nail polishes ageing. To guarantee the innocuousness of nail polishes, the maximal value of 466 ppb of cumulated nitrosamines (NDMA, NDEA, NMor, NDELA) has been proposed by Swiss authorities. Nevertheless, to guarantee the highest quality and security level for consumer, there is a need to find an efficient way to degrade and prevent from the formation of nitrosamines in nail polishes, trying to totally suppress them.
Study results
We analysed the evolution of the concentration of the 4 most commonly found nitrosamines: nitrosodimethylamine (NDMA), nitrosodiethylamine (NDEA), nitrosomorpholine (NMor) and nirsodiethanolamine (NDELA). Nitrosamines quantification has been performed by GC-MSMS with a quantification limit of 5 ppb. A genuine method of sample preparation has been set up for nail polish, specifically developed in ILCosmetics Group, under the direction of Robin Cisneros and Frederic Derosier by Benjamin Forquin.
To determine the activity of maltol as anti-nitrosamines agent, we evaluated its ability to hinder the formation of nitrosamines and its nitrosamines degradation activity in nail polishes. We first worked on ideal nail polishes, formulated in laboratory and totally nitrosamine free at formulation to demonstrate maltol efficiency, after what we realised a 30 months statistical study on a hundred of randomly sampled industrial production batches with and without maltol. All the results of this study are available in annex of this article.
Limitation of nitrosamines formation
After 30 months of ageing, the presence of maltol strongly limits the formation of all four studied nitrosamines. Strongest effects are observed with NDEA for which a total degradation is evidenced, and with NMor for which the average concentration is divided by 50. Concentrations of NDMA and NDELA remain low even without maltol, but using it divides their concentration by a factor 2 to 4.
The use of maltol keeps nitrosamines average concentration in levels corresponding to the quantification limits of our analysis method during over 30 months of ageing of nail polishes.
Degradation of nitrosamines brought by raw materials
First of all we can observe that the average total amount of nitrosamines in industrial batches of nail polishes after production is around 150 ppb, with a rather important standard deviation. This presence of nitrosamines in freshly produced nail polishes comes from technically unavoidable traces contained by raw materials while the important standard deviation is explained by the important varieties of sampled formulas for this study. This evidences the fact that raw materials play a major role in initial pollution of nail polishes (nacres, pigments, glitters, mattifying agents, etc.). However, during all the study and regardless tested shades, with or without maltol, the global nitrosamines level observed remained below the 466 ppb limit stated as safe by Swiss authorities.
When we compare the evolution of the concentration of nitrosamines between nail polishes, we observe that the total amount of nitrosamines decreases in the presence of maltol, leading to relatively low levels, below 100 ppb after an average of 3 months from production.
This compared study of the evolution of total nitrosamines concentration in nail polishes confirms that maltol can hinder the formation of nitrosamines in a nail polish and degrade traces of such pollutants coming from raw materials. The use of maltol in a nail polish as anti-nitrosamines agent has been patented . Furthermore, results obtained through this study lead us to work with much more care with raw materials evaluation to limit the ones containing technically unavoidable traces of nitrosamines.
Conclusion
Thanks to this 3 years study based on ideal nail polishes produced in laboratory and totally free of nitrosamines and a hundred of randomly sampled industrial nail polish batches; we evidenced the double efficiency of maltol as anti-nitrosamine agent.
This tiny natural organic molecule acts as an inhibitor if nitrosamines formation as well as a degradation agent of such pollutants. Thus, the nail polishes formulas with maltol guarantee a very low amount of nitrosamines —and even null if the nail polish was free from nitrosamines at its production— during over 30 months.
Results of the study realised on industrial batches of nail polishes randomly sampled pushed us to investigate much more carefully our raw materials to reduce at a maximum the ones containing traces of nitrosamines.
Then, considering the demonstrated efficiency of maltol as anti-nitrosamines agent and the hindsight on raw materials given by this 3 years study, ILCosmetics Group is now in capacity to provide nail polishes with minimal amount of nitrosamines during all their shelf life, guaranteeing always cleaner and safer products.
