Pesticides are a class of chemical compounds that are used for the purpose of managing agriculture and ensuring that a sufficient amount of food is produced. Pesticides can be found in natural compounds or they are of synthetic origin. The widespread use of pesticides can have negative impacts on the environment and society as it is potentially toxic to animals and humans. In the Master's thesis, we investigated further the toxicological aspect of the use of ten selected pesticides, with an emphasis on their endocrine function. We chose green tea as the subject of the research, since China and Japan, which are the main importers of tea, rank high in terms of pesticide use compared to other countries. In order to evaluate the toxicological aspect of the use of pesticides, we first focused on their physical and chemical properties. We also examined the regulations considering pesticides, in the European Union and in Slovenia. To give an easier idea of how toxic a particular compound is, we also collected data on people's exposure to pesticides, as well as the possible health consequences of acute or chronic exposure. The toxicity of these compounds can be manifested, among other things, as abnormalities in the reproductive system and defects in the development of the fetus. Therefore we decided to investigate whether selected pesticides can potentially act as hormonal disruptors on the endocrine system.
Research of literature sources has shown that quite a few of the studied compounds act as endocrine disruptors. Most of them cannot be classified as safe chemicals, as there is not enough relevant data, and the determination of endocrine action is also complicated by the complexity of the action and binding of these molecules to endocrine receptors. We also predicted the endocrine activity by employing the Endocrine disruptome software. Our predictions showed that out of the ten pesticides involved in the research cypermethrin has the greatest potential for binding to various nuclear receptors, which is in agreement with the findings of other researchers. Carbendiazim, dicofol, endosulfan sulfate and imidacloprid also proved to be of some concern on account of their nuclear receptor binding capacities. Based on the Endocrine disruptome predictions, we assessed that acetamiprid, chlorpitifos, thiacloprid, methomyl and flonicamid are not cause for concern.
We then focused on determining the presence of pesticides in the green tea sample using chromatographic methods - we focused on trying to identify selected pesticides in a mix of standards and potentially in green tea sample, but not on concentration of said pesticides. We started developing the method on an HPLC-UV device, where we managed to optimize it to the extent, that we identified 8 out of 10 pesticide standards with narrow and high peaks in the chromatogram. The optimized chromatographic method was transferred to the UHPLC-MS system, where pesticide standards were initially injected. Despite the fact, that used column and parameters did not differ from the previous analysis, we were not able to detect all standards. This is likely attributed to the rapid degradation of pesticides and the fragmentation of the analyte due to the dissociation caused by the collision in the ion source.
We prepared the green tea sample using the Strata-X-C® cartridge, where we managed to retain only one of the pesticides on the cartridge - thiacloprid. Thus we can conclude that the green tea sample did not contain thiacloprid, at least not in concentrations that could be detected, but we cannot claim that it did not contain any of the other nine pesticides investigated, since we did not detect them in control samples.
|
