Bioacumulação de cianotoxinas em hortaliças irrigadas com águas eutrofizadas de reservatórios superficiais do semiárido.

Abstract

The eutrophication of reservoirs favors the emergence of cyanobacteria and cyanotoxins in their waters, which are commonly used to irrigate agricultural crops. This has generated concern, due to the potential for bioaccumulation of cyanotoxins in vegetables intended for human consumption. In this scenario, the objective of this work was to evaluate the bioaccumulation of cyanotoxins in vegetables irrigated with eutrophicated waters from surface reservoirs in the Brazilian semi-arid region. The work was divided into three chapters. Chapter I was focused on the introduction of the topic, the justification of the work and the bibliographic review, where the need and importance of carrying out research on the problem addressed was verified. In Chapter II, the focus was to study the bioaccumulation of microcystins (MCs), cylindrospermopsin (CYN) and saxitoxin (STX) in vegetables irrigated with water from the Epitácio Pessoa reservoir, an important water source in the State of Paraíba. Cyanotoxin analyzes were performed using the ELISA method. It was found that, at the point of collection for irrigation, the water from the Epitácio Pessoa reservoir was eutrophic and contained MCs, CYN and STX. MCs showed greater bioaccumulation potential in the vegetables studied and coriander and parsley were more prone to accumulation. It was found that the irrigation method influenced cyanotoxin concentrations in certain regions of the plant and that peppers with different ages did not show a significant difference in bioaccumulation. Finally, it was found that the estimated daily intakes (EDIs) of cyanotoxins from the vegetables evaluated were lower than the recommended total daily intakes (TDIs). In Chapter III, the focus was to evaluate the bioaccumulation of MCs, CYN and STX in lettuce and coriander irrigated with eutrophicated waters from a surface reservoir in the rural area of Pocinhos, Paraíba, with emphasis on determining a better solvent, between water and methanol, for the extraction of MCs, CYN and STX from plant tissues; and the effects of plant age and the use of sodium hypochlorite (NaClO) as a sanitizer on the concentrations of MCs, CYN and STX accumulated in vegetables. The analysis of cyanotoxins was once again carried out using the ELISA method. It was found that the water in the studied reservoir was eutrophic and contained MCs, CYN and STX. Once again, MCs showed greater potential for bioaccumulation in the vegetables studied and coriander proved to be more prone to accumulation. Methanol proved to be the most suitable solvent for extracting MCs, CYN and STX, cleaning with NaClO was not effective in degrading these toxins and the age of the plant had a positive influence on the clearance of CYN, however the same was not observed for MCs and STX. Finally, it was found that the CDEs of MCs from coriander exceeded the TDI recommended by the WHO by up to 3.61 times, and that 70 g of the studied lettuce would also be enough to exceed the TDI of MCs. The CDEs of CYN and STX from lettuce and coriander were lower than the recommended TDIs. In general, the risk of bioaccumulation of cyanotoxins in vegetables associated with the increasing eutrophication of waters from semi-arid reservoirs has become evident and points to the need to implement quality parameters that encompass cyanotoxins in irrigation waters, in order to guarantee the production of healthy and safe food for human consumption and thus protect public health.