Nitrosamines are known carcinogens and genotoxins that were first detected in cosmetics in 1977. They are formed as a reaction product of a nitrosamine precursor, usually a secondary amine, and a nitrosating agent. Substances that can lead to the formation of nitrosamines enter the cosmetic product as an ingredient or impurity of an ingredient. The nitrosation reaction is further catalysed/inhibited by the presence of nitrosation catalysts/inhibitors. In Slovenia, the field of nitrosamines in cosmetic products is regulated by the EU Cosmetic Directive. It specifies that nitrosamines may be present as impurities only up to 50 µg/kg.
In our thesis, we have evaluated which cosmetic products are most likely to contain nitrosamines, which nitrosamines are present and which ingredients may lead to the formation of nitrosamines, based on a review of scientific publications. We found that N-nitrosodiethanolamine is the most common nitrosamine in cosmetics, forming from diethanolamine in the presence of a nitrosating agent. Nitrosamines were most frequently detected in shampoos whose main ingredients are surfactants, which are often precursors of nitrosamines. Based on the results of a review of scientific publications, we decided to investigate the composition of shampoos on the Slovenian market, including shampoos from a Slovenian online drugstore and a Slovenian online pharmacy. Among the ingredients, we looked for nitrosamine precursors, nitrosating agents as well as catalysts and inhibitors of nitrosation. About 9% of the 391 shampoos studied contained a nitrosamine precursor or nitrosating agent. The majority of them also contained nitrosation inhibitors and none contained a nitrosation catalyst. We found that none of the shampoos contained both a nitrosamine precursor and a nitrosating agent. None of the shampoos contained banned secondary amines and ingredients banned in the EU Cosmetic Directive.
Finally, we used the RAPEX system, which is used for the rapid exchange of information on dangerous products intended for consumers in the European Union, to identify cosmetic products that were recalled from the market due to excessive nitrosamine levels. Most of the cases involved excessive levels of N-nitrosodiethanolamine. Shampoos were among the most frequently recalled products. The low number of recalled cosmetic products (10) is not in line with the results of scientific publications, indicating that the verification of the safety of products on the market is insufficient and needs to be more controlled.
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