A full life-cycle bioassay with Cantareus aspersus shows reproductive effects of a glyphosate-based herbicide suggesting potential endocrine disruption

One-step electrodeposition of MWCNTs-Cu MOF films for the ratiometric electrochemical analysis of glyphosate

Sensitive and accurate determination of glyphosate (GLYP) is vital for food safety and environmental protection. Herein, a novel electrochemical ratiometric biosensor was designed for the accurate quantification of GLYP through one-step electrodeposition of MWCNTs-Cu MOF films. MWCNTs-Cu MOF nanostructures were directly electro-synthesized in situ on the electrode from the precursor solution. The combination of Cu MOFs with MWCNTs not merely improved the conductivity of MOFs, but also enhanced the sensitivity of the biosensor. Furthermore, Cu sites within Cu MOFs were turned into CuCl to further amplify the current signal and enable the specific recognition of GLYP through competing reactions with the transformation of CuCl into non-electroactive Cu-GLYP. Meanwhile, internal reference molecules of methylene blue (MB) were incorporated to improve the measurement accuracy of GLYP for reducing unpredictable measurement errors aroused by environmental deviations. The ratiometric electrochemical sensor exhibited a high linearity with the logarithmic value of GLYP concentration from 0.5 nM to 400 nM. The detection limit was estimated to be as low as 0.014 nM. Finally, the present sensor with ratiometric signal export was applied for GLYP analysis in real samples with high sensitivity and accuracy. The simplicity and reliability of the ratiometric sensor make it a worthy and powerful tool for food and environmental monitoring. This design strategy also provides an avenue for the development of simple and efficient biosensors for other substances.

Subacute exposure to Roundup® changes steroidogenesis and gene expression of the glutathione-glutaredoxin system in rat ovaries: Implications for ovarian toxicity of this glyphosate-based herbicide

Studies have indicated that glyphosate induces endocrine disruption and may adversely affect the male reproductive system. However, evidence of its effects on ovarian function is poorly understood so far, making further studies necessary on the mechanisms of the glyphosate toxicity in the female reproductive system. The aim of this work was to evaluate the effect of a subacute exposure (28 days) to the glyphosate-based formulation Roundup® (1.05, 10.5 and 105 μg/kg b.w. of glyphosate) on steroidogenesis, oxidative stress, systems involved in cell redox control and histopathological parameters in rat ovaries. Hence we quantify plasma estradiol and progesterone by chemiluminescence; non-protein thiol levels, TBARS, superoxide dismutase and catalase activity by spectrophotometry; gene expression of steroidogenic enzymes and redox systems by real-time PCR; and ovarian follicles by optical microscopy. Our results demonstrated that oral exposure increased progesterone levels and the mRNA expression of 3β-hydroxysteroid dehydrogenase. Histopathological analysis revealed a decrease in the number of primary follicles and an increase in the number of corpus luteum in rats exposed to Roundup®. An imbalance of the oxidative status was also evidenced by decreasing the catalase activity at all groups exposed to the herbicide. Increased lipid peroxidation and gene expression of glutarredoxin and decreased of glutathione reductase were also observed. Our results indicate that Roundup® causes endocrine disruption of hormones related to female fertility and reproduction and changes the oxidative status by altering antioxidant activity, inducing lipid peroxidation, as well as changing the gene expression of the glutathione-glutarredoxin system in rat ovaries.

Evaluation of the developmental toxicity of solvents, metals, drugs, and industrial chemicals using a freshwater snail (Biomphalaria glabrata) assay

A freshwater snail assay was employed to assess the embryotoxicity of solvents including acetone, methanol, ethanol, isopropanol, dimethyl-sulfoxide, glycerin, metals/metalloids including mercuric chloride (HgCl₂), cadmium chloride (CdCl₂,), antimony salts Sb⁺³ and Sb⁺⁵, drugs including colchicine, hydroxyurea, cyclophosphamide, an industrial chemical sodium azide (SA), an anionic surfactant dodecyl sodium sulfate-(DSS), H₂O₂ and sodium chloride (NaCl). The assay consists of exposing Biomphalaria glabrata egg masses (EM) to the substances for 96-hr and following up embryo/snail development for lethality, abnormal morphology (teratogenicity), and day of hatching up to day 10 or 14 after spawning. Based upon concentration-response relationships, LC_50%s (embryolethality), EC_50%s (teratogenicity) and IC_50%s (hatching retardation) and 95%CIs were determined for tested chemicals. The LOECs indicated that HgCl₂ (37 nM) and CdCl₂ (140 nM) are potent embryotoxic agents in snails. Teratogenic indices (TI = LC₅₀/EC₅₀) for almost all tested chemicals were lower than or close to unity suggesting that these compounds were not teratogenic in this assay. The snail assay may be adequately performed in a cost-effective standardized protocol which enables testing a number of environmental chemicals over a broad concentration range. The snail assay needs to undergo further validation to be recognized for an internationally harmonized hazard identification in ecotoxicity risk assessment.

Effects of glyphosate on zebrafish: a systematic review and meta-analysis

Glyphosate herbicide is widely used in worldwide crop production. Consequently, its active ingredient, surfactants, and adjuvants commonly reach the aquatic ecosystem, thereby harming the biota. An investigation into how this herbicide affects aquatic species is important, especially in fish, as they have the ability to absorb and concentrate toxins. We aimed to evaluate the effects of glyphosate on the embryonic, larval and adult stages of zebrafish (Danio rerio), an appreciable organismal model. In this sense, we performed a meta-analysis using published articles from online databases (PubMed and ScienceDirect), which covered studies published until 2022. From a massive compilation of studies evaluating the effects of active substance glyphosate and Glyphosate-Based Herbicides (GBH) on zebrafish, we selected 36 studies used in downstream analyses. Overall, we report that glyphosate affects developmental stages and demonstrates toxicity and damage in zebrafish. We observed that embryos exposed to glyphosate exhibit increased mortality. There was also an increase in the number of morphological abnormalities related to yolk sac oedema, pericardial oedema, spinal curvature and body malformations, and a decrease in body size was observed. Furthermore, there was a decrease in the number of beats. The biochemical results demonstrated an increase in reactive oxygen species and antioxidant capacity against peroxyl radicals in the gills. The literature shows that glyphosate decreased the distance covered and the mean speed of the animals and increased the number of rotations. We concluded that glyphosate causes damage in the embryonic, larval and adult stages of this species. These results are valid for zebrafish and can be applied to other freshwater fish species. Graphical abstract.

Field mixtures of currently used pesticides in agricultural soil pose a risk to soil invertebrates

Massive use of pesticides in conventional agriculture leads to accumulation in soil of complex mixtures, triggering questions about their potential ecotoxicological risk. This study assessed cropland soils containing pesticide mixtures sampled from conventional and organic farming systems at La Cage and Mons, France. The conventional agricultural field soils contained more pesticide residues (11 and 17 versus 3 and 11, respectively) and at higher concentrations than soils from organic fields (mean 6.6 and 10.5 versus 0.2 and 0.6 μg kg^-1, respectively), including systemic insecticides belonging to neonicotinoids, carbamate herbicides and broad-spectrum fungicides mostly from the azole family. A risk quotient (RQ_i) approach evaluated the toxicity of the pesticide mixtures in soil, assuming concentration addition. Based on measured concentrations, both conventional agricultural soils posed high risks to soil invertebrates, especially due to the presence of epoxiconazole and imidacloprid, whereas soils under organic farming showed negligible to medium risk. To confirm the outcome of the risk assessment, toxicity of the soils was determined in bioassays following standardized test guidelines with seven representative non-target invertebrates: earthworms (Eisenia andrei, Lumbricus rubellus, Aporrectodea caliginosa), enchytraeids (Enchytraeus crypticus), Collembola (Folsomia candida), oribatid mites (Oppia nitens), and snails (Cantareus aspersus). Collembola and enchytraeid survival and reproduction and land snail growth were significantly lower in soils from conventional compared to organic agriculture. The earthworms displayed different responses: L. rubellus showed higher mortality on soils from conventional agriculture and large body mass loss in all field soils, E. andrei showed considerable mass loss and strongly reduced reproduction, and A. caliginosa showed significantly reduced acetylcholinesterase activity in soils from conventional agriculture. The oribatid mites did not show consistent differences between organic and conventional farming soils. These results highlight that conventional agricultural practices pose a high risk for soil invertebrates and may threaten soil functionality, likely due to additive or synergistic "cocktail effects".

Advances in organophosphorus pesticides pollution: Current status and challenges in ecotoxicological, sustainable agriculture, and degradation strategies

Organophosphorus pesticides (OPPs) are one of the most widely used types of pesticide that play an important role in the production process due to their effects on preventing pathogen infection and increasing yield. However, in the early development and application of OPPs, their toxicological effects and the issue of environmental pollution were not considered. With the long-term overuse of OPPs, their hazards to the ecological environment (including soil and water) and animal health have attracted increasing attention. Therefore, this review first clarified the classification, characteristics, applications of various OPPs, and the government's restriction requirements on various OPPs. Second, the toxicological effects and metabolic mechanisms of OPPs and their metabolites were introduced in organisms. Finally, the existing methods of degrading OPPs were summarized, and the challenges and further addressing strategy of OPPs in the sustainable development of agriculture, the environment, and ecology were prospected. However, methods to solve the environmental and ecological problems caused by OPPs from the three aspects of use source, use process, and degradation methods were proposed, which provided a theoretical basis for addressing the stability of the ecological environment and improving the structure of the pesticide industry in the future.

Investigating the Effects of Pesticides on Ramshorn Snails (Planorbella [Helisoma] trivolvis) Infected with Echinostoma spp

Globally, parasite-induced diseases in humans and wildlife are on the rise, and pesticide pollution may be a contributing factor. Echinostoma spp. trematode parasites are prominent in North America, and they use ramshorn snails (Planorbella [Helisoma] trivolvis) as intermediate hosts. We investigated the impact of chronic exposure to 1 of 5 pesticide treatments (control, or 50 μg/L of atrazine, glyphosate, carbaryl, or malathion) on uninfected and Echinostoma-infected snails for 41 d in the laboratory. We recorded snail mortality, the number of egg masses laid, change in mass, and behavior. Chronic exposure to atrazine, carbaryl, and malathion significantly decreased snail survival, whereas parasite infection status or exposure to glyphosate did not. Pesticide and parasite treatments did not influence growth or behavior, but parasite infection caused complete reproductive failure in snail hosts. Our results indicated that the direct effects of pesticides could threaten snail populations in natural environments and disrupt host-parasite dynamics.  Environ Toxicol Chem 2021;40:2755-2763. © 2021 SETAC.

Toxicological Effects of Roundup® on Drosophila melanogaster Reproduction

Herbicide use has increased dramatically since 2001, particularly Roundup®. Effective in agricultural practice, Roundup® adversely affects non-target organisms, including reproductive and endocrine systems. We exposed fruit flies, Drosophila melanogaster, to either Roundup® Ready to Use, containing pelargonic acid and glyphosate, or Roundup® Super Concentrate, that includes glyphosate and POEA, at sublethal concentrations. Both Roundup® formulations reduced ovary volume with fewer mature oocytes, most adversely at the highest concentration tested. Flies exposed within 2 h of eclosion were affected more than at 4 h, suggesting a critical period of increased ovarian sensitivity. These results support multi-species evidence that glyphosate-based herbicides interfere with normal development of the reproductive systems of non-target organisms.

Combining human and snail indicators for an integrative risk assessment of metal(loid)-contaminated soils

With the new soil uses such as land restoration and to protect wilderness, the human health risk assessment (HHRA) and environmental risk assessment (ERA) should be combined. Based on the relationships demonstrated between an indicator of soil quality, the land snail, and human exposure, the aim of this study is to examine the snail and human risk indicators for twenty-nine soils contaminated by metal(loid)s. HHRA was evaluated by both hazard quotient and carcinogenic risk. When the human health indicators were ranked as uncertain, they were weighted by bioaccessibility to refine the risk assessment. The ERA was performed with risk coefficient after ex situ snail exposure. The results showed strong and novel relationships between human health and environmental risk indicators that had never been found before. For 62% of the soils, both indicators revealed either a confirmed risk or an uncertain level of risk. Overall pollutants present greater risk for human than for environment, with 55 vs 28% of the studied soils classified in the proven risk, respectively. An original integrative risk assessment of polluted soils has been proposed, that shall help setting up relevant strategies to manage contaminated soils considering not only human but also environmental indicators of risk.

From bioavailability to risk assessment of polluted soil using snails: link between excess transfer and inhibition of sexual maturation

An accurate assessment of the environmental risk of soils contaminated by metal(loid)s (MEs) requires quantifying exposure and knowing the toxicity of contaminants transferred to biota. For this purpose, two indices have been developed with the bioindicator Cantareus aspersus to assess exposure (SET: sum of the excess of transfer) and risk (ERITME: evaluation of the risk of the transferred metal elements) of multi-contaminated soils. If the SET and ERITME indices allow characterization of exposure and risk based on unspecific toxicity points, then the link between these indices and real effects on some toxicological endpoints, such as growth or sexual maturation, remains to be demonstrated. For this purpose, sub-adult snails were exposed for 28 days to 38 ME-contaminated soils. Relationships between the SET and/or ERITME indices and health alterations in C. aspersus were determined using Spearman correlations, linear regressions, univariate regression trees, and kinetic models. Relationships were determined between the values of the SET and ERITME indices, bioaccumulation as an indicator of ME bioavailability, and the alteration in physiological endpoints, such as the shell development used as a non-invasive indicator of sexual maturation. The results enabled the determination of three levels of risk according to the differences in reaching sexual maturity: no risk, uncertain, and proven risk depended on whether the value of ERITME was below, in, or beyond the interval [2574-22720], respectively. This study provides the first benchmarks with the SET and ERITME indices to interpret the risk of contaminated soils to snails and to relate the environmental and toxicological bioavailability of ME mixtures.

Bioconcentration of glyphosate in wetland biofilms

Wetland biofilms were exposed to the herbicide glyphosate via in situ field exposures and controlled microcosm experiments to measure bioconcentration and metabolism of glyphosate by biofilm organisms. Concentrations of glyphosate in biofilms were two to four orders of magnitude higher than the surrounding water, bioconcentration factors averaged 835 and 199 L·kg-1 in field- and lab-exposed biofilms, respectively. Glyphosate in water where it had been detected in biofilms at field-exposed sites ranged from below detection (<1 μg·L-1) up to 130 μg·L-1. Bioconcentration of glyphosate in biofilms was inversely proportional to concentrations in the surrounding water, and the retention kinetics were similar to both adsorption and enzymatic models. Microorganisms present in both the water and biofilms metabolized glyphosate to its primary breakdown product aminomethyl phosphonic acid (AMPA), with increased rates of breakdown in and around the biofilms. Photosynthetic efficiency of the algae within the biofilms was not affected by 24 h controlled glyphosate exposures. Our results demonstrate the role of biofilms in improving wetland water quality by removing contaminants like glyphosate, but also as a potential exposure route to higher trophic levels via consumption. Due to bioconcentration of pesticides, exposure risk to organisms consuming or living in biofilms may be much higher than indicated by concentrations in ambient water samples.

Impact of ageing and soil contaminants on telomere length in the land snail

Telomeres (TLs) are non-coding DNA sequences that are usually shortened with ageing and/or chemical exposure. Bioindicators such as the land snail can be used to assess the environmental risk of contaminated soils. As for most invertebrates, the evolution of TLs with ageing or exposure to contaminants is unknown in this mollusc. The aims of this study were to explore the relationships between ageing, contaminant exposure, sublethal effects and TL length in the terrestrial gastropod Cantareus aspersus. TL length was investigated in haemocytes from five age classes of C. aspersus. The impact of contaminants on sub-adult snails exposed to Cd, Hg or a mixture of polycyclic aromatic hydrocarbons (PAHs) in soils for one or two months was studied. Bioaccumulation, growth, sexual maturity and TLs were measured. TL attrition was significant for the juvenile and sub-adult stages, but not later. Exposure to Cd increased the mortality (around 30%). Exposure to polluted soils inhibited growth (19-40%) and sexual maturity (6-100%). Although the health of the snails exposed to Cd, Hg and PAHs was altered, TL length in haemocytes was not disturbed, suggesting a high capacity of this snail species to maintain its TLs in haemocytes under chemical stress. These results first address TL length in snails and reveal that the relationship commonly proposed for vertebrates between TL shortening and ageing or exposure to contaminants cannot be generalized.

Evaluation of apoptotic potential of glyphosate metabolites and impurities in human peripheral blood mononuclear cells (in vitro study)

Glyphosate is used for cereal, vegetable and fruit crops for reducing or inhibiting the growth of weeds as well as a desiccant for various grain crops. That is why, glyphosate has been shown to be accumulated in humans and animals through ingestion of food of both plant and animal origin. The study aimed to assessed the effect of glyphosate, its metabolites: aminomethylphosphonic acid (AMPA), methylphosphonic acid and its impurities: PMIDA, N-methylglyphosate, hydroxymethylphosphonic acid and bis(phosphonomethyl)amine on apoptosis induction in human peripheral blood mononuclear cells (PBMCs). PBMCs were exposed to the compounds studied at the concentrations ranging from 0.01 to 5 mM for 4 h. We have observed an increase in reactive oxygen species (including hydroxyl radical) and cytosolic calcium ions levels as well as reduction of transmembrane mitochondrial potential (ΔΨm) in PBMCs exposed to the compounds examined. All substances studied changed PBMCs membrane permeability, activated caspase-8, -9, -3 and caused chromatin condensation, which showed that they were capable of inducing apoptosis both via extrinsic and particularly intrinsic pathway. Generally the study demonstrated that there were no differences between apoptotic changes induced by glyphosate, its metabolites or impurities, and observed changes were provoked by high concentrations of investigated compounds.

Roundup®, but Not Roundup-Ready® Corn, Increases Mortality of Drosophila melanogaster

Genetically modified foods have become pervasive in diets of people living in the US. By far the most common genetically modified foods either tolerate herbicide application (HT) or produce endogenous insecticide (Bt). To determine whether these toxicological effects result from genetic modification per se, or from the increase in herbicide or insecticide residues present on the food, we exposed fruit flies, Drosophila melanogaster, to food containing HT corn that had been sprayed with the glyphosate-based herbicide Roundup®, HT corn that had not been sprayed with Roundup®, or Roundup® in a variety of known glyphosate concentrations and formulations. While neither lifespan nor reproductive behaviors were affected by HT corn, addition of Roundup® increased mortality with an LC50 of 7.1 g/L for males and 11.4 g/L for females after 2 days of exposure. Given the many genetic tools available, Drosophila are an excellent model system for future studies about genetic and biochemical mechanisms of glyphosate toxicity.

Cytotoxic and genotoxic effect of oxyfluorfen on hemocytes of Biomphalaria glabrata

Chemicals released from anthropogenic activities such as industry and agriculture often end up in aquatic ecosystems. These substances can cause serious damage to these ecosystems, thus threatening the conservation of biodiversity. Among these substances are pesticides, such as oxyfluorfen, a herbicide used for the control of grasses and weeds. Considering its widespread use, it is important to investigate the possible toxicity of this compound to aquatic organisms, especially invertebrates. Hence, the use of biological systems able to detect such effects is of great importance. The mollusk Biomphalaria glabrata has been shown to be useful as an environmental indicator to assess the potential ecological effects of physical and chemical stressors in freshwater environments. The present study sought to detect mutagenic changes in hemocytes of B. glabrata exposed to oxyfluorfen. To perform these tests, this study used ten animals per group, exposed acutely (48 h) and chronically (15 days) to oxyfluorfen. The herbicide concentrations were 0.125, 0.25, and 0.5 mg/L. The results showed that oxyfluorfen induced significant frequencies of micronuclei, binucleated cells, and apoptosis in hemocytes of mollusks when compared to the control group. Unlike chronic exposure, acute exposure was dose-dependent. The present study's results demonstrate the cytotoxic and genotoxic effects of oxyfluorfen on hemocytes of B. glabrata.

An integrative omics approach to unravel toxicity mechanisms of environmental chemicals: effects of a formulated herbicide

The use of integrative molecular approaches can aid in a comprehensive understanding of the effects of toxicants at different levels of biological organization, also supporting risk assessment. The present study aims to unravel the toxicity mechanisms of a widely used herbicide to the arthropod Folsomia candida exposed in a natural soil, by linking effects on reproduction, proteomics and genome-wide gene expression. The EC50 effects on reproduction over 4 weeks was 4.63 mg glyphosate/kg of soil. The formulation included a polyethoxylated tallowamine as an adjuvant, which at 50% effect on reproduction had an estimated concentration of 0.87-1.49 mg/kg of soil. No effects were observed on survival and reproduction when using the isolated active substance, pointing the toxicity of the formulated product to the co-formulant instead of the active ingredient, glyphosate. RNA sequencing and shotgun proteomics were applied to assess differential transcript and protein expressions between exposed and control organisms in time, respectively. Specific functional categories at protein and transcriptome levels were concordant with each other, despite overall limited correlations between datasets. The exposure to this formulation affected normal cellular respiration and lipid metabolism, inducing oxidative stress and leading to impairment in biological life cycle mechanisms such as molting and reproduction.

Cigarette butts may have low toxicity to soil-dwelling invertebrates: Evidence from a land snail

Cigarette butts are a common form of litter that is often deposited on soil, where toxins from butts may affect soil-dwelling organisms. We examined possible toxicity of cigarette butts to the woodland snail Anguispira alternata using a toxicity study with cigarette butt effluent and a lab-based habitat choice experiment in which snails could feed or rest on areas with different butt densities. No mortality occurred during the 32-day toxicity study, which used six effluent concentrations ranging from 0 to 4butts/l (0 to 0.92butts/kg of soil). Neither food consumption nor snail growth differed among the effluent concentrations. When provided a choice among four habitats with 0 to 4 cigarette butts, snails selected to preferentially rest in the 0-butt habitat and avoided the 4-butt habitat. This distribution pattern was strong during the first wk. but became weaker over time and largely disappeared by the end of the 3-wk experiment. Snails did not discriminate among butt densities when feeding. This is the first toxicity test using cigarette butts on soil-dwelling invertebrates. Declining aversion to cigarette butts over a 3-wk period may indicate declining toxicity of terrestrially deposited butts as they age, but further testing is needed.