Lipophilic properties of pesticides: bioaccumulation and biomagnification in animals, the toxicity forecasting (review)

The problem of pesticides contamination save actuality because of the growing demand for food and multi-factorial processes of their biotransformation and bioaccumulation in living organisms. As of July 11, 2023, more than 1,200 approved insecticides, acaricides and herbicides have been registered in Russian Federation (excluding fungicides, rodenticides, repellents, desiccants, plant growth regulators, microbiological and biological pesticides, etc.), many of them are included in the list of particularly dangerous according to PAN data, for example, diazinon, chlorpyrifos, dimethoate, imidacloprid, malathion, spinosad (PAN List of HHPs, 2021). Their uncontrolled using results the accumulation of parent compounds, metabolites and degradation products in soil, water, plants, and animals and the subsequent biomagnification of persistent pollutants at higher trophic levels (V.P. Kalyabina et al., 2021; C.M. Volschenk et al., 2019; Z. Zhang et al., 2019). Pesticides have an adverse effect not only for target pests, but also on the crops, soil microbiota, natural ecosystems objects and humans. Biopesticides are safer, but at the same time, their high selectivity becomes a disadvantage in solving several agrotechnical objectives (W.-H. Leong et al., 2020; De O.H. Gomes et al., 2020). The absorption, distribution, and transport of pesticides in biological systems are determined by their lipophilicity (T. Chmiel et al., 2019; R. Beiras, 2018; S.-K. Kim et al., 2019). High lipophilicity generates conditions for high metabolic clearance of compounds. The biological activity of substances in the organism could be predicted by logP which describes their affinity for target proteins (T. Chmiel et al., 2019), where P is the distribution coefficient showing the ratio of the compound concentrations in two immiscible phases at equilibrium state. The extremely lipophilicity of pesticides (logP > 5) can result to their binding to hydrophobic targets, which provides non-selectivity and higher toxicity (C. Olisah et al., 2021). Insufficient data has been obtained on the metabolism and bioaccumulation of pesticides in farm animals and synergistic effects in real conditions by this time. The distribution of pesticides in soil, ground and surface waters depends not only on their lipophilicity, but on pH, temperature, the initial amounts of preparations, organic and inorganic substances content, solids sorption properties (S.D. Burlaka et al., 2019; S. Hintze et al., 2021; F.A.P.C. Gobas et al., 2018). The accumulation of pesticides in the soil results the decreasing of the involved in the circulation of elements and organic substances degradation soil microorganism activity and can be the biological indicator of ecosystems pollution. Generally, the levels of pesticide residues in environment are measured by gas, high-performance and ultra-high-performance liquid chromatography, enzyme immunoassay and capillary electrophoresis (A. Samsidar et al., 2018; S. Hintze et al., 2021; L. Fu et al., 2018). Gas chromatography is appropriate for volatile and thermally stable compounds, while high-performance liquid chromatography is more relevant for non-volatile and polar compounds. A combination of chromatographic separation with high-resolution mass spectrometry could be required for non-targeted analysis that allows the not detected in the target study compounds identification and determination. The search for safe plant protection substances and forecasting of their toxicity, bioaccumulation processes in environment and the transfer through food chains, is possible using a combination of two approaches. These are «non-targeted search» and modern QSAR mathematical models. The «non-targeted search» allows both targeted and non-targeted analysis of pesticides and their metabolites, and QSAR models are based on the correlation of physicochemical, particularly lipophilic properties of molecules and their effects on living organisms (A. Speck-Planche, 2020; N.A.Ilyushina, 2019; O.G. Columbin, 2020).