Some of you may have heard about the Rapex procedure. The RAPEX System is a European system designed to quickly exchange information about the hazards resulting from the use of consumer goods. Every week, an update of hazardous products and of the corrective measures taken is published online. Among the product classes concerned, cosmetics are regularly pointed at due to nitrosamines. This odd name recently made the headlines again. But what are nitrosamines?
Nitrosamines are nitrogenous substances which form in many different, both plant and animal environments. They are formed during a nitrosation reaction between nitrites or nitrates and amines or amides. They have been known for over 100 years and the presence of nitrosamines in certain products is not a new issue: Magee and al confirmed their carcinogenicity as soon as 1976, maybe even earlier. Indeed, 90% of nitrosamines exhibited a carcinogenic power on many organs in all the animal species tested. And nothing seems to show that Man can resist the carcinogenic activity of N-nitrosated compounds.
A meeting in 1977 in the USA resulted in a warning against these substances. Concerns about the contamination of cosmetics by N-nitrosamines, mainly in the form of NDELA, date back to at least 1979 (United States Federal Register Notice, 44 FR 21365, April 10, 1979). N-nitrosamine traces in cosmetics can come from the use of specific cosmetic ingredients and/or from the nitrosation of precursors, in particular secondary amines found in finished cosmetic products (Harvey et al. 1994).
Experiments soon evidenced their presence in some products, in particular in the food industry. The risk mainly concerned food, meat, tin cans, etc. But also pharmaceuticals. Some drugs were recently suspected of containing nitrosamines: rapamycin, Zantac, losartan…
But cosmetics are also concerned. In fact, certain ingredients involved in the formation of nitrosamines are widely used in some cosmetic formulas: alkanolamines, in particular triethanolamine, nitrates, nitrated derivatives, etc. The products concerned include: foaming products, shampoo, bath & shower products, mascara, nail polish…
N-nitrosamines are covered by European regulations on cosmetics. The 15th Directive 92/86/EEC of the European Commission on cosmetic products bans the marketing of cosmetic products containing nitrosamines. The presence of traces in cosmetics is tolerated if the said traces are technically inevitable, as long as the product has no negative effect on human health when applied under the reasonably predictable conditions of use. Although no specific level was provided for in finished cosmetic products, it involves maintaining N-nitrosamine levels as low as reasonably possible. In one Directive, a limit of 50 µg·kg-1 (i.e. part per billion or ppb) was set for the level of N–nitroso di–n-alkanol amines in fatty acid dialkanolamides, monoalkanolamines, and trialkanolamines used as raw materials in cosmetic products. By extension, this limit served as reference for finished products. A European Directive on foodstuffs made things a bit clearer in 1997. Then, in 2003, European Directive 2003/83 of 24/09/2003 provided precise conditions for this group of substances, in particular the use of alkanolamines. Meanwhile, progress was made with analytical methods to put an end to these issues. But it is a key, recurring matter given the extremely low limits of detection required.
This characteristic would only have a limited interest if this reaction did not result, in many cases, in the formation of such substances in finished products. Given this situation, the industry took measures to maintain nitrosamine levels as low as possible. For foaming products, this action led to replacing ingredients based on alkanolamines, still complying with the conditions of use. For mascaras, it resulted in reformulations by adjusting alkanolamine doses (TEA) or qualities (MEA or DEA), or even in removals by substituting them for highly hydrophilic surfactants to preserve the products’ good wetting power and, consequently, a good brush/lash transfer.
Nail polish is a cosmetic product mainly based on nitrocellulose as film-forming agent, and organomodified clay (stearalkonium bentonite) to guarantee the suspension of pigments and mother-of-pearls, while ensuring a seamless application on the nails. As nail polish ages, nitrocellulose very slowly deteriorates, becoming a source of nitrites. On the other hand, secondary amines can be contained as traces or form over time in organomodified clays. For example, although nitrosamine precursors are never used in nail polish formulas, it is clear that as time goes by, nail polish can lead to the formation of molecules responsible for the appearance of nitrosamines.
To guarantee the safety of nail polish, the maximum value should be the lowest possible. So, rather than creating controversies about doses, IL Cosmetics and International Lacquers, in partnership with the CSTA, tried to find an efficient way to prevent the formation or presence of nitrosamine traces and get completely rid of them. They eventually chose to add maltol. Maltol is a small natural organic molecule which belongs to the pyranone family. It is a long-known antioxidant, but whose effect on nitrosamines in nail polish had neither been demonstrated nor even explored yet. Since it is soluble in the organic matrix of nail polish, the work consisted in assessing its potential of inhibition of the formation and degradation of nitrosamines in nail polish. After a three-year research programme, it was shown that this natural organic molecule acted both as an inhibitor of the formation of nitrosamines and a degradation agent of this family of pollutants. It helps regulate the presence of these undesirable substances at an extremely low level in preparations.
The results of the study conducted on random industrial nail polish also helped investigate raw materials much more in depth. Studies on ageing showed this effect lasts over time.
This work and its applications are the subject of a patent WO2019091923A1
This most interesting work helped the International Lacquer company make progress in controlling the global quality level of their products. In addition, it highlights the – sometimes overlooked – work done as part of a constant search for excellence.
Congratulations to International Lacquers and IL Cosmetics.