Parabens are the most commonly used preservatives in the cosmetic industry. We can find them in the pharmaceutical and food industry also. Because of their method of use, it is very difficult to avoid the intake of parabens in the aquatic environment. In the aquatic environment halogen elements, such as chlorine and bromine are present on many occasions. Parabens can react with chlorine and bromine which leads to the emergence of halogenated degradation products. Because parabens are classified in the group of weak endocrine disruptors, it is very important to know their path in the aquatic environment and their influence on live organisms. In the thesis, we predicted environmental influence, acute toxicity, and endocrine functioning for seven different parabens, para-hydroxybenzoic acid (PHBA), and their halogenated degradation products by means of two programs, i.e. Endocrine disruptome and VegaNIC. The logP value influences the path of parabens in the environment importantly. We were also interested in the probability of their biological degradation, resistance against biodegradation, and bioaccumulation factor (BCF). In predicting the resistance of parabens, we ascertained that there is the same pattern in all of them. The biggest probability of degradation is for the original paraben. Biological degradation of very little probability is characteristic for mono- and dichlorinated products. Brominated degradation products are biologically non-degradable, which means that they are far more resistant in the environment in comparison to the original parabens. We classified methylparaben with lowest BCF value as the least resistant. The most resistant was benzylparaben. The results of acute toxicity showed that the most toxic is benzylparaben. It is followed by butylparaben and iso-butylparaben. The highest LC50 value and thus the least toxicity proved methylparaben. The results gained by in silico methods showed that brominated derivatives are more acutely toxic as chlorinated derivatives of the same paraben. In researching endocrine functioning, the results showed that the highest probability is binding to androgen and thyroid receptors (AR, AR an and TR α and TR β). The possibility of binding did not increase by the degradation of the original paraben. On the basis of all results gained by means of computer programs, we estimated that the safest is methylparaben because it had the lowest logP value, low acute toxicity, and low BCF value which classifies it among substances who are not bioaccumulated. According to the results, the most toxic paraben is benzylparaben and its brominated degradation products because they have a high logP value, are the most acute toxic, and have a high affinity of binding to the androgenic receptor and the medium possibility of binding to thyroid receptors. Parabens were believed as safe ingredients for a long time. Lately, however, there is an increasing amount of research which rejects this hypothesis. We could surely say that the mentioned preservatives do not represent a very high risk in the environment because they do not emerge in very high concentrations. In the future, however, further research will be necessary mostly in the field of their endocrine functioning and the connection with the emergence of breast cancer.
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