Icelandic moss, with the Latin name Cetraria islandica, is commonly used in the pharmaceutic industry. It is mostly used as a plant extract to soothe a sore throat and to heal upper respiratory tract infections. Due to the components present in the extract, it is lately also increasingly used in the cosmetic industry. The extract can be used in various types of cosmetic products; its properties are suitable for skin care cosmetics as well as for cosmetics intended for the mucous membranes. Extracts show a huge variation in qualitative and quantitative structure which is mainly affected by its environment and growing conditions. To this end, we must take extra care when handling the extract and follow the recommendations and instructions for use, based on the safety assessment. In this thesis we have conducted a safety assessment for the Icelandic moss extract with the use of the threshold of toxicological concern (TTC) approach, which evaluates the compounds with the implementation of the Cramer classification scheme providing the exposure limits (TTC values). We have examined the qualitative and quantitative compositions of the actual plant and extract based on the literature and determined the potential extent of absorption based on the physicochemical properties of each individual compound. These values in addition to the concentration of the compounds have enabled us to calculate the systemic exposure when using cosmetic products containing this extract. Due to the varied and complex chemical composition of the plant extract it is clear that they contain compounds, whose concentrations are not known. In this case, we have determined the maximal tolerated systemic exposure of the compounds based on the range of the absorption potential and the TTC values from the Cramer classification scheme. For some of the compounds, we have also calculated the acceptable daily intake by employing the NOAEL values, which in all cases were significantly higher than the TTC values and the potential systemic exposure via the extract. The latter was very low for most of the compounds and did not exceed the TTC values based on the Cramer classification scheme of systemic toxicity due to its low absorption through the skin. Still, some of the compounds showed systemic exposure above the permitted levels that are somewhat conservative and higher levels for these limits have already been recommended. Despite some slight deviation in the values, we have managed to declare the Icelandic moss extract to be safe to use under normal conditions, based on all calculations and acquired values.
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