Towards a strategic approaches in alternative tests for pesticide safety

Joint survival modelling for multiple species exposed to toxicants

In environmental risk assessment (ERA), the multitude of compounds and taxa demands cross-species extrapolation to cover the variability in sensitivity to toxicants. However, only the impact of a single compound to a single species is addressed by the general unified threshold model of survival (GUTS). The reduced GUTS is the recommended model to analyse lethal toxic effects in regulatory aquatic ERA. GUTS considers toxicokinetics and toxicodynamics. Two toxicodynamic approaches are considered: Stochastic death (SD) assumes that survival decreases with an increasing internalized amount of the toxicant. Individual tolerance (IT) assumes that individuals vary in their tolerance to toxic exposure. Existing theory suggests that the product of the threshold z_w and killing rate b_w (both SD toxicodynamic parameters) are constant across species or compounds if receptors and target sites are shared. We extend that theory and show that the shape parameter β of the loglogistic threshold distribution in IT is also constant. To verify the predicted relationships, we conducted three tests using toxicity studies for eight arthropods exposed to the insecticide flupyradifurone. We confirmed previous verifications of the relation- between SD parameters, and the newly established relation for the IT parameter β. We enhanced GUTS to jointly model survival for multiple species with shared receptors and pathways by incorporating the relations among toxicodynamic parameters described above. The joint GUTS exploits the shared parameter relations and therefore constrains parameter uncertainty for each of the separate species. Particularly for IT, the joint GUTS more precisely predicted risk to the separate species than the standard single species GUTS under environmentally realistic exposure. We suggest that joint GUTS modelling can improve cross-species extrapolation in regulatory ERA by increasing the reliability of risk estimates and reducing animal testing. Furthermore, the shared toxicodynamic response provides potential to reduce complexity of ecosystem models.

Green synthesis of metal-based nanoparticles for sustainable agriculture

The large-scale use of conventional pesticides and fertilizers has put tremendous pressure on agriculture and the environment. In recent years, nanoparticles (NPs) have become the focus of many fields due to their cost-effectiveness, environmental friendliness and high performance, especially in sustainable agriculture. Traditional NPs manufacturing methods are energy-intensive and harmful to environment. In contrast, synthesizing metal-based NPs using plants is similar to chemical synthesis, except the biological extracts replace the chemical reducing agent. This not only greatly reduces the used of traditional chemicals, but also produces NPs that are more economical, efficient, less toxic, and less polluting. Therefore, green synthesized metal nanoparticles (GS-MNPs) are widely used in agriculture to improve yields and quality. This review provides a comprehensive and detailed discussion of GS-MNPs for agriculture, highlights the importance of green synthesis, compares the performance of conventional NPs with GS-MNPs, and highlights the advantages of GS-MNPs in agriculture. The wide applications of these GS-MNPs in agriculture, including plant growth promotion, plant disease control, and heavy metal stress mitigation under various exposure pathways, are summarized. Finally, the shortcomings and prospects of GS-MNPs in agricultural applications are highlighted to provide guidance to nanotechnology for sustainable agriculture.

A scientometric analysis of ecotoxicological studies with the herbicide atrazine and microalgae and cyanobacteria as test organisms

Atrazine (ATZ) is one of the most widely used herbicides in the world. A scientometric study was conducted to analyze the evolution of research on ATZ. The study also looked at the use of microalgae and cyanobacteria as biological models for toxicity tests during the period from 1959 to 2019, in the category of toxicology of Web of Science. The results show an increase in the number of scientific publications mainly in the USA, Canada, and China. The majority of papers was published in journals with high impact factors, demonstrating the relevance of such studies. About 83% of the studies aimed to evaluate the effect of ATZ on non-target organisms. From those, 7.5% included microalgae and cyanobacteria. The majority of them worked with chlorophyceae to perform toxicity bioassays of ATZ and analyze its sublethal effects. The gaps identified by this analysis included a small number of collaborations between research groups from different countries; the number of studies with terrestrial organisms, which are larger in comparison to aquatic organisms; and the fact that none of the studies with ATZ and microalgae was performed in the field. These findings can point out to researchers and funding agencies the gaps in knowledge on the toxic effects of ATZ and guide the development of new research projects as well as environmental policies.

Environment permissible concentrations of glyphosate in drinking water can influence the fate of neural stem cells from the subventricular zone of the postnatal mouse

The developing nervous system is highly vulnerable to environmental toxicants especially pesticides. Glyphosate pesticide induces neurotoxicity both in humans and rodents, but so far only when exposed to higher concentrations. A few studies, however, have also reported the risk of general toxicity of glyphosate at concentrations comparable to allowable limits set up by environmental protection authorities. In vitro data regarding glyphosate neurotoxicity at concentrations comparable to maximum permissible concentrations in drinking water is lacking. In the present study, we established an in vitro assay based upon neural stem cells (NSCs) from the subventricular zone of the postnatal mouse to decipher the effects of two maximum permissible concentrations of glyphosate in drinking water on the basic neurogenesis processes. Our results demonstrated that maximum permissible concentrations of glyphosate recognized by environmental protection authorities significantly reduced the cell migration and differentiation of NSCs as demonstrated by the downregulation of the expression levels of the neuronal ß-tubulin III and the astrocytic S100B genes. The expression of the cytoprotective gene CYP1A1 was downregulated whilst the expression of oxidative stresses indicator gene SOD1 was upregulated. The concentration comparable to non-toxic human plasma concentration significantly induced cytotoxicity and activated Ca2+ signalling in the differentiated culture. Our findings demonstrated that the permissible concentrations of glyphosate in drinking water recognized by environmental protection authorities are capable of inducing neurotoxicity in the developing nervous system.

Innovative strategy based on mechanisms to substitute animal testing for ocular toxicity assessment of agrochemical formulations market in Brazil

Considering the successful employment of alternative methods for eye toxicity assessment of products for regulatory purposes, and the recent advances in Brazilian legislative scenario, which adopted the UN GHS classification system for agrochemical formulations toxicity assessment, there is an emerging demand for strategies that allow the evaluation of such products. Based on this, the present study aimed to address the applicability of a mechanistic-based defined approach for eye toxicity assessment of agrochemical formulations. It was investigated the opacity/permeability, depth and location of corneal injury in bovine cornea, and vascular events in chorioallantoic membrane induced for different Brazilian agrochemicals using a Sequential Testing Strategy (STS). Cytotoxicity induced by the agrochemical formulations was evaluated by Short Time exposure (STE) (OECD TG 491) assay (step 1), corneal injury was investigated by standard Bovine Corneal Opacity and Permeability (BCOP) (OECD TG 437) followed by histopathological evaluation (step 2), and Hen Chorionic-allantoic Membrane test (HET-CAM) was used to evaluate vascular injury (step 3). The results demonstrated that the proposed defined approach enabled a classification corresponding UN GHS classification of agrochemical formulations while minimizing the use of live animals. Therefore, this approach may be useful for categorization of agrochemicals in Brazil according to the new regulatory scenario.

Nanotechnology as a new sustainable approach for controlling crop diseases and increasing agricultural production

Climate change will negatively affect crop production by exacerbating the incidence of disease and decreasing the efficacy of conventional approaches to disease control. Nanotechnology is a promising new strategy for plant disease management that has many advantages over conventional products and approaches, such as better efficacy, reduced input requirements, and lower eco-toxicity. Studies on crop plants using various nanomaterials (NMs) as protective agents have produced promising results. This review focuses on the use of NMs in disease management through three different mechanisms: (i) as antimicrobial agents; (ii) as biostimulants that induce plant innate immunity; and (iii) as carriers for active ingredients such as pesticides, micronutrients, and elicitors. The potential benefits of nanotechnology are considered, together with the role that NMs might play in future disease management and crop adaptation measures.

Sequential assessment via daphnia and zebrafish for systematic toxicity screening of heterogeneous substances

Environment and organisms are persistently exposed by a mixture of various substances. However, the current evaluation method is mostly based on an individual substance's toxicity. A systematic toxicity evaluation of heterogeneous substances needs to be established. To demonstrate toxicity assessment of mixture, we chose a group of three typical ingredients in cosmetic sunscreen products that frequently enters ecosystems: benzophenone-3 (BP-3), ethylhexyl methoxycinnamate (EHMC), and titanium dioxide nanoparticle (TiO2 NP). We first determined a range of nominal toxic concentration of each ingredient or substance using Daphnia magna, and then for the subsequent organismal level phenotypic assessment, chose the wild-type zebrafish embryos. Any phenotype change, such as body deformation, led to further examinations on the specific organs of transgenic zebrafish embryos. Based on the systematic toxicity assessments of the heterogeneous substances, we offer a sequential environmental toxicity assessment protocol that starts off by utilizing Daphnia magna to determine a nominal concentration range of each substance and finishes by utilizing the zebrafish embryos to detect defects on the embryos caused by the heterogeneous substances. The protocol showed additive toxic effects of the mixtures. We propose a sequential environmental toxicity assessment protocol for the systematic toxicity screening of heterogeneous substances from Daphnia magna to zebrafish embryo in-vivo models.

Saccharomyces cerevisiae as a model in ecotoxicological studies: A post-genomics perspective

The budding yeast Saccharomyces cerevisiae represents a well-consolidated and widely used eukaryotic model, with a number of features that make it an ideal organism to carry out functional toxicological studies. Several advantages are permitted by the use of yeast cells, as the possibility to identify molecular biomarkers, unknown mechanisms of action and novel potential targets. Thanks to the evolutionary conservation, yeast can provide also useful clues allowing the prioritization of more complex analyses and toxicity predictions in higher eukaryotes. The last two decades were incredibly fruitful for yeast "omics", but referring to the analysis of the effects of pesticides on yeast much still remains to be done. Furthermore, a deeper knowledge of the effects of environmental pollutants on biotechnological processes associated with the use of yeasts is to be hoped.

Evaluation of Eye Irritation Potential of Solid Substance with New 3D Reconstructed Human Cornea Model, MCTT HCE(TM)

The eye irritation potential of drug candidates or pharmaceutical ingredients should be evaluated if there is a possibility of ocular exposure. Traditionally, the ocular irritation has been evaluated by the rabbit Draize test. However, rabbit eyes are more sensitive to irritants than human eyes, therefore substantial level of false positives are unavoidable. To resolve this species difference, several three-dimensional human corneal epithelial (HCE) models have been developed as alternative eye irritation test methods. Recently, we introduced a new HCE model, MCTT HCE^TM which is reconstructed with non-transformed human corneal cells from limbal tissues. Here, we examined if MCTT HCE^TM can be employed to evaluate eye irritation potential of solid substances. Through optimization of washing method and exposure time, treatment time was established as 10 min and washing procedure was set up as 4 times of washing with 10 mL of PBS and shaking in 30 mL of PBS in a beaker. With the established eye irritation test protocol, 11 solid substances (5 non-irritants, 6 irritants) were evaluated which demonstrated an excellent predictive capacity (100% accuracy, 100% specificity and 100% sensitivity). We also compared the performance of our test method with rabbit Draize test results and in vitro cytotoxicity test with 2D human corneal epithelial cell lines.