Both acute glyphosate and the aminomethylphosphonic acid intoxication decreased the acetylcholinesterase activity in rat hippocampus, prefrontal cortex and gastrocnemius muscle

It has been reported that glyphosate, one of the most common herbicides used in agriculture, impairs locomotion and cognition. Glyphosate has a variable half-life in soil up to biotic and/or abiotic factors transform the molecule in metabolites such as the aminomethylphosphonic acid (AMPA) that has a longer half-life. In this study, female Sprague Dawley rats were acutely exposed to different doses of glyphosate or AMPA (i.e. 10, 56 or 100 mg/kg) and, subsequently, the acetylcholinesterase (AChE) activity was measured in the hippocampus, prefrontal cortex (PFC) and the gastrocnemius muscle. Both glyphosate and AMPA produced a similar decrease in the AChE activity in all the tissues tested. These results suggest that interference with normal cholinergic neurotransmission may be one of the mechanisms involved in glyphosate-induced motor alterations in rats. Moreover, our results highlight the biological importance of AMPA as a molecule with anticholinesterase action in brain and skeletal muscle. To our knowledge, this is the first report showing in vivo that AMPA, the major metabolite of glyphosate, behaves as an organophosphate.

Exposure of children to glyphosate in Morocco: Urinary levels and predictors of exposure

Glyphosate is one of the most frequently used organophosphorus plant protection products worldwide, and has recently been classified as probably carcinogenic to humans by the International Agency for Research and Cancer (IARC). We aimed to evaluate the urinary levels of glyphosate and its metabolite aminomethylphosphonic acid (AMPA) in Moroccan children, to identify the main predictors and to perform a risk assessment. Data was collected during a cross sectional study of 48 children from an intensive agricultural area. Measurements included a questionnaire on life-style, socio-demographic and herbicide exposures. Urinary glyphosate and AMPA were extracted using solid phase extraction (SPE) and analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Overall, glyphosate and AMPA were detected in 73% and 75% of urine samples, respectively. The mean concentrations were 0.97 μg L^-1 (2.06 μg/g_creatinine) for glyphosate and 0.79 μg L^-1 (1.52 μg/g_creatinine) for AMPA. Children younger than 5 years had a higher AMPA and glyphosate urine concentration (mean = 2.24 μg L^-1; estimation coefficient (EC) = 1.39; 95% CI: 0.54-2.24) (mean = 4.05 μg L^-1; EC = 2.92; 95% CI: 1.68-4.15), respectively, than children aged 6-12. Children living near the pesticide spraying fields (<50 m) had 14.91 μg L^-1 and 2.35 μg L^-1 more glyphosate and AMPA, respectively, than children living in urban counties (95% CI: 8.14-20.91 for glyphosate and 95% CI: 0.55-4.14 for AMPA). AMPA concentration varied significantly with the source of drinking water, AMPA was higher among children that used water from open water sources (mean = 1.49 μg L^-1; EC = 2.98; 95% CI/0.67-5.78) compared to those using water from closed water sources. There were also non-significant associations found, such as total household net income, current parental job description, and dietary intake. With the regard to the health risk assessment, estimated daily intake (EDIs), hazard quotient (HQs), and a hazard index (HI) were calculated. The GMs of EDI were 4.38 and 2.26 μg/kg of body weight BW/day for glyphosate and AMPA, respectively. The HQs were calculated considering 0.5 mg/kg BW/day as an acceptable daily intake (ADI), which EFSA has established as a health-based reference value for both analytes. The value obtained were lower than 1, and therefore, low health risk due to glyphosate and AMPA was expected for the target population under the study. This study provides further evidence on factors associated with glyphosate exposure, especially in developing countries.

Environmental behaviour of a pesticide metabolite, the AMPA. Sequestration of Ca2+, Mg2+, Cu2+, Zn2+ and Al3. CHEMOSPHERE 2022;306:135535. [PMID: 35792217 DOI: 10.1016/j.chemosphere.2022.135535]

The chelating and sequestering ability of a glyphosate metabolite, the aminomethylphosphonic acid (AMPA) towards bi- and trivalent metal cations, such as Ca²⁺, Mg²⁺, Zn²⁺, Cu²⁺ and Al³⁺, were investigated in aqueous solutions of NaCl, in an ionic strength range of 0.1 ≤ I/mol dm^-3 ≤ 1.0 and at constant temperature of T = 298.15 ± 0.15 K. The investigations on the acid-base properties and complexing ability were performed, by means of potentiometry, in conditions of different c_M:c_AMPA molar ratios and pH values. The formation of insoluble species was experimentally observed in the Mⁿ⁺/AMPA^2- systems, and the solid phases were characterized by means of X-Ray Diffractometry (XRD), Scanning Electron Microscopy (SEM) and InfraRed Attenuated Total Reflection spectroscopy (IR-ATR). The dependence on ionic strength of the stability constants of the Mⁿ⁺/AMPA^2- complexes species, determined at different ionic strengths, was modelled by the Debye-Hückel type equation. The sequestering ability of AMPA toward the investigated metal cations was evaluated by pL_0.5 parameter.

Influence of glyphosate and its metabolite aminomethylphosphonic acid on aquatic plants in different ecological niches

Glyphosate and its metabolite aminomethylphosphonic acid (AMPA) draw great concern due to their potential threat to aquatic ecosystems. The individual and combined effects of glyphosate and AMPA on aquatic plants in different ecological niches need to be explored. This study aimed to investigate the ecotoxicity of glyphosate and AMPA on the emergent macrophyte Acorus calamus, phytoplankton Chlorella vulgaris, and submerged macrophyte Vallisneria natans after their exposure to glyphosate and AMPA alone and to their mixture. Medium and low concentrations of glyphosate (≤ 0.5 mg L^-1) significantly inhibited the growth of V. natans and promoted the growth of C. vulgaris (P < 0.05) but had no significant effect on the growth of A. calamus (P > 0.05). AMPA (≤ 5.0 mg L^-1) did not significantly influence the relative growth rate (except C. vulgaris) or malonaldehyde levels but significantly altered the expression levels of chlorophyll-related genes and superoxide dismutase [Cu-Zn] genes in the aquatic plants examined. AMPA mainly affected the oxidative phosphorylation pathway in V. natans and not those in other two plants, indicating that V. natans was more sensitive to AMPA-induced oxidative damage. Moreover, antagonistic effects on plant growth were observed when plants were exposed to low concentrations of glyphosate + AMPA (≤ 0.1 + 0.1 mg L^-1). When the concentration of glyphosate + AMPA reached 0.5 + 0.5 and 5.0 + 5.0 mg L^-1, the growth of the submerged macrophyte was additively or synergistically inhibited, but the growth of the emergent macrophyte and phytoplankton was antagonistically inhibited. Our results indicated that both the individual and combined effects of glyphosate and AMPA might alter the vertical structure of shallow lakes and accelerate the conversion of shallow lakes from grass-based to algal-based lakes.

Glyphosate infiltrates the brain and increases pro-inflammatory cytokine TNFα: implications for neurodegenerative disorders

BACKGROUND

Herbicides are environmental contaminants that have gained much attention due to the potential hazards they pose to human health. Glyphosate, the active ingredient in many commercial herbicides, is the most heavily applied herbicide worldwide. The recent rise in glyphosate application to corn and soy crops correlates positively with increased death rates due to Alzheimer's disease and other neurodegenerative disorders. Glyphosate has been shown to cross the blood-brain barrier in in vitro models, but has yet to be verified in vivo. Additionally, reports have shown that glyphosate exposure increases pro-inflammatory cytokines in blood plasma, particularly TNFα.

METHODS

Here, we examined whether glyphosate infiltrates the brain and elevates TNFα levels in 4-month-old C57BL/6J mice. Mice received either 125, 250, or 500 mg/kg/day of glyphosate, or a vehicle via oral gavage for 14 days. Urine, plasma, and brain samples were collected on the final day of dosing for analysis via UPLC-MS and ELISAs. Primary cortical neurons were derived from amyloidogenic APP/PS1 pups to evaluate in vitro changes in Aβ40-42 burden and cytotoxicity. RNA sequencing was performed on C57BL/6J brain samples to determine changes in the transcriptome.

RESULTS

Our analysis revealed that glyphosate infiltrated the brain in a dose-dependent manner and upregulated TNFα in both plasma and brain tissue post-exposure. Notably, glyphosate measures correlated positively with TNFα levels. Glyphosate exposure in APP/PS1 primary cortical neurons increases levels of soluble Aβ40-42 and cytotoxicity. RNAseq revealed over 200 differentially expressed genes in a dose-dependent manner and cell-type-specific deconvolution analysis showed enrichment of key biological processes in oligodendrocytes including myelination, axon ensheathment, glial cell development, and oligodendrocyte development.

CONCLUSIONS

Collectively, these results show for the first time that glyphosate infiltrates the brain, elevates both the expression of TNFα and soluble Aβ, and disrupts the transcriptome in a dose-dependent manner, suggesting that exposure to this herbicide may have detrimental outcomes regarding the health of the general population.

Aminomethylphosphonic acid (AMPA) alters oxidative status during embryonic development in an amphibian species

Glyphosate's primary metabolite (aminomethylphosphonic acid, AMPA) is known to alter embryonic development at environmentally relevant concentrations in amphibians. However, we have limited understanding of the physiological mechanisms through which AMPA affects organisms. In this study, we tested whether alteration of the oxidative status is one mechanism through which AMPA affects organism performance. To this end, we analysed several oxidative status markers in hatchling tadpoles that were exposed to sublethal concentrations of AMPA during embryonic development (~16 days). We compared the influence of environmentally relevant concentrations of AMPA (from 0.07 to 3.57 μg l^-1) on the relation between developmental traits (i.e, embryonic development duration, embryonic mortality and hatchling size) and oxidative status markers known to alter homeostasis when unbalanced (superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), thiols and ratios thereof). We included measures of telomere length as an indicator of physiological state. We found that AMPA concentrations induce non-monotonic effects on some oxidative status markers with hatchlings displaying elevated antioxidant responses (elevated thiols and unbalanced SOD/(GPx + CAT) ratio). The lack of effect of AMPA on the relation between developmental traits, oxidative status and telomere length suggests that selective mortality of embryos susceptible to oxidative stress may have occurred prior to hatching in individuals less resistant to AMPA which display lower hatching success. Future studies are required to disentangle whether oxidative unbalance is a cause or a consequence of AMPA exposition. This study highlights the need to investigate effects of the metabolites of contaminants at environmental concentrations to comprehensively assess impacts of anthropogenic contamination on wildlife.

AMPA-15N - Synthesis and application as standard compound in traceable degradation studies of glyphosate

Stable isotope labeling of pollutants is a valuable tool to investigate their environmental transport and degradation. For the globally most frequently used herbicide glyphosate, such studies have, so far, been hampered by the absence of an analytical standard for its labeled metabolite AMPA-15N, which is formed during the degradation of all commercially available glyphosate isotopologues. Without such a standard, detection and quantitation of AMPA-15N, e.g. with LC-MS/MS, is not possible. Therefore, a synthetic pathway to AMPA-15N from benzamide-15N via the hemiaminal was developed. AMPA-15N was obtained in sufficient yield and purity to be used as a standard compound for LC-MS/MS analysis. Suitable MS-detection settings as well as a calibration using the internal standard (IS) approach were established for Fmoc-derivatized AMPA-15N. The use of different AMPA isotopologues as IS was complicated by the parallel formation of [M+H]+ and [M]+• AMPA-Fmoc precursor ions in ESI-positive mode, causing signal interferences between analyte and IS. We recommend the use of either AMPA-13C-15N, AMPA-13C-15N-D2 or a glyphosate isotopologue as IS, as they do not affect the linearity of the calibration curve. As a proof of concept, the developed analysis procedure for AMPA-15N was used to refine the results from a field lysimeter experiment investigating leaching and degradation of glyphosate-2-13C-15N. The newly enabled quantitation of AMPA-15N in soil extracts showed that similar amounts (0.05 - 0.22 mg·kg-1) of the parent herbicide glyphosate and its primary metabolite AMPA persisted in the topsoil over the study period of one year, while vertical transport through the soil column did not occur for either of the compounds. The herein developed analysis concepts will facilitate future design and execution of experiments on the environmental fate of the herbicide glyphosate.

One-step purification/extraction method to access glyphosate, glufosinate, and their metabolites in natural waters

A new green method for trace level quantification of four herbicides, glyphosate (GLYP), glufosinate (GLUF), and their main metabolites, aminomethylphosphonic acid (AMPA) and 3-(methyl-phosphinico)-propionic acid (MPPA), was developed. The purification step without any derivatization was conducted by solid-phase extraction using Chelex-100 resin in the Fe (III) form, followed by elution with 5% NH4OH. The four analytes were quantified by ultra-high-performance liquid chromatography coupled to tandem mass spectrometry. The developed extraction method was validated on five fresh and sea water matrices with mean recoveries ranging from 80.1% to 109.4% (relative standard deviation < 20%). The extraction conditions were evaluated and certified for the high applicability of the extraction method too. The limits of detection (ng/L) in the five water matrices were in ranges 0.70 - 4.0, 2.4 - 3.9, 1.8 - 4.7, and 1.6 - 4.0 for GLYP, AMPA, GLUF, and MPPA, respectively. The method was successfully applied to detect the four compounds in surface waters sampled along the Red River Delta region in July 2019. The highest concentrations were detected at 565, 1,330, 234, and 871 ng/L for GLYP, AMPA, GLUF, and MPPA, respectively. These results showed the potential capacity of this new method for convenient monitoring of herbicides and their metabolites in the diverse natural water system.

LC-MS/MS characterisation and determination of dansyl chloride derivatised glyphosate, aminomethylphosphonic acid (AMPA), and glufosinate in foods of plant and animal origin

Glyphosate and other polar and acidic pesticides have been particularly studied due to the concerns over widespread and intensive use. The chemical properties of these compounds necessitate use of customised methods, such as derivatisation or ion exchange chromatography. These approaches present a compatibility problem with ESI-MS due to presence of salts and non-volatile compounds. For that reason, a simple procedure has been developed for the extraction, pre-column derivatisation with dansyl chloride (5-(dimethylamino)naphthalene-1-sulfonyl chloride), and mass spectrometric detection of glyphosate, AMPA, and glufosinate after the separation on a C₁₈stationary phase. The dansyl derivatives were characterised with ESI-MS and their separation from derivatisation reagent byproducts was demonstrated with UV absorption detection. Reagent byproducts eluted before the analytes and were separated from the analytes completely, thus the proposed procedure did not contaminate the mass spectrometers. The proposed procedure was evaluated with respect to the matrix effects and extraction efficiency, and was validated with different mass spectrometers for milk, cucumber, honey, porridge formula, bovine kidney and liver matrix. The LOQ was 10 μg kg^-1 for AMPA and glufosinate, and 10-25 μg kg^-1for glyphosate, depending on matrix. Measurement uncertainties ranged from 4 to 44%. Method performance was compared to the QuPPe (Quick Polar Pesticides) procedure in combination with a diethylamino-based column from Waters™. In the case of Orbitrap™ detection, the proposed procedure had a comparable performance to the QuPPe procedure. Although, improved peak shape, higher absolute peak intensity, and lower standard deviation of the calibration curve slope was observed with the proposed procedure. This could be explained by the superior electrospray stability and lower extent of ion suppression.

Binding interaction of glyphosate with glyphosate oxidoreductase and C-P lyase: Molecular docking and molecular dynamics simulation studies

Widespread application of glyphosate poses a threat to living organisms. Microbial strains are able to degrade glyphosate via contrasting metabolic pathways with the help of enzymes. Glyphosate oxidoreductase (GOX) and C-P lyase are the key enzymes for the biodegradation of glyphosate and its intermediate metabolite aminomethylphosphonic acid (AMPA) in microbes. The microbial degradation of glyphosate has been reported, but the underlying molecular mechanism is still unclear. Therefore, in this study, the interaction mechanism of GOX and C-P lyase with glyphosate and AMPA were investigated by using molecular docking and molecular dynamics (MD) simulations. The results indicate that glyphosate contacts with the active site of GOX and C-P lyase by hydrogen bonds as well as hydrophobic and van der Waals interactions in aqueous solution to maintain its stability. The presence of glyphosate and AMPA in the active site significantly changes the conformation of GOX and C-P lyase. The results of the MD simulations confirm that GOX and C-P lyase complexes are stable during the catalytic reaction. This study offers a molecular level of understanding of the expression and function of GOX and C-P lyase for the bioremediation of glyphosate.

Environmental behavior and influencing factors of glyphosate in peach orchard ecosystem

In this paper, several experiments were carried out to study the environmental behavior and influencing factors of glyphosate (PMG) in peach orchard ecosystem. The results of field experiments showed that PMG and its metabolite aminomethylphosphonic acid (AMPA) were detected in peach tree leaves and peach tree fruits, although PMG was only sprayed on the soil. The residues of PMG and AMPA in peach tree leaves were ~0.1 mg/kg and ~0.5 mg/kg and in peach tree fruits were ~0.01 mg/kg and 0.07-0.11 mg/kg, respectively. By conducting a series of laboratory simulation experiments, the environmental factors affecting the degradation of PMG were screened and evaluated. The results showed that PMG metabolized much faster in loess soil than red soil and black soil (with the DT50 of 11.6 days, 62.4 days, and 34.1 days, respectively). By analyzing the basic properties of the soil, we investigated the effects of pH, moisture content, organic matter (exogenous biochar) and ambient temperature using orthogonal experiments, and the results were further confirmed by microbial experiment. The results showed that alkaline conditions (pH = 7.8/9), high water content (25%) and microorganisms could promote the degradation of PMG. Sterile soil environment had a negative impact on the metabolic behavior of PMG to AMPA.

Analysis of glyphosate, aminomethylphosphonic acid, and glufosinate from human urine by HRAM LC-MS

Aminomethylphosphonic acid (AMPA) is the main metabolite of glyphosate (GLYP) and phosphonic acids in detergents. GLYP is a synthetic herbicide frequently used worldwide alone or together with its analog glufosinate (GLUF). The general public can be exposed to these potentially harmful chemicals; thus, sensitive methods to monitor them in humans are urgently required to evaluate health risks. We attempted to simultaneously detect GLYP, AMPA, and GLUF in human urine by high-resolution accurate-mass liquid chromatography mass spectrometry (HRAM LC-MS) before and after derivatization with 9-fluorenylmethoxycarbonyl chloride (Fmoc-Cl) or 1-methylimidazole-sulfonyl chloride (ImS-Cl) with several urine pre-treatment and solid phase extraction (SPE) steps. Fmoc-Cl derivatization achieved the best combination of method sensitivity (limit of detection; LOD) and accuracy for all compounds compared to underivatized urine or ImS-Cl-derivatized urine. Before derivatization, the best steps for GLYP involved 0.4 mM ethylenediaminetetraacetic acid (EDTA) pre-treatment followed by SPE pre-cleanup (LOD 37 pg/mL), for AMPA involved no EDTA pre-treatment and no SPE pre-cleanup (LOD 20 pg/mL) or 0.2-0.4 mM EDTA pre-treatment with no SPE pre-cleanup (LOD 19-21 pg/mL), and for GLUF involved 0.4 mM EDTA pre-treatment and no SPE pre-cleanup (LOD 7 pg/mL). However, for these methods, accuracy was sufficient only for AMPA (101-105%), while being modest for GLYP (61%) and GLUF (63%). Different EDTA and SPE treatments prior to Fmoc-Cl derivatization resulted in high sensitivity for all analytes but satisfactory accuracy only for AMPA. Thus, we conclude that our HRAM LC-MS method is suited for urinary AMPA analysis in cross-sectional studies.

Sensitive and selective quantification of glyphosate and aminomethylphosphonic acid (AMPA) in urine of the general population by gas chromatography-tandem mass spectrometry

Glyphosate is the highest volume herbicide used worldwide, and its main biodegradation product is aminomethylphosphonic acid (AMPA), both are listed as priority substances in the Human Biomonitoring for Europe (HBM4EU) initiative which aims at improving policy by filling knowledge gaps by targeted research. The objective of the current study was to advance the sensitivity of an existing gas chromatography-tandem mass spectrometry analytical method to measure environmental population exposures. A 50% lower limit of quantification of 0.05 µg/L was achieved for both analytes by slight modifications in sample work-up, and use of another isotope labelled internal standard. In a pilot study, 41 urine samples from the general German population were analysed, of which glyphosate and AMPA could be quantified in 66% and 90% of the samples respectively, which is sufficient to reliably describe distributions of urinary concentrations in the non-occupationally exposed population.

Aminomethylphosphonic acid alters amphibian embryonic development at environmental concentrations

Despite intense societal and scientific debates regarding glyphosate toxicity, it remains the most widely used herbicide. The primary metabolite of glyphosate, AMPA (aminomethylphosphonic acid), is the main contaminant detected in surface waters worldwide, both because of the extensive use of glyphosate and because of other widespread sources of AMPA (i.e., industrial detergents). Studies on potential effects of glyphosate using environmentally relevant concentrations of AMPA on non-target wildlife species are lacking. We experimentally tested the effects of AMPA on embryonic development in a common European toad at concentrations spanning the range found in natural water bodies (from 0.07 to 3.57 μg l^-1). Our experimental concentrations of AMPA were 100-6000 times lower than official Predicted-No-Effect-Concentrations. We found that these low-level concentrations of AMPA decreased embryonic survival, increased development duration and influenced hatchling morphology. Response patterns were more complex than classical linear concentration-response relationships, as concentration responses were nonmonotonic, with greater effects at low-concentrations of AMPA than at high levels. Based on our results we recommend that investigators focus not only on effects of "parent compounds," but also their metabolites at environmentally relevant concentrations in order to comprehensively assess impacts of anthropogenic contaminants on the environment.

Occurrence and transformation of phosphonates in textile dyeing wastewater along full-scale combined treatment processes

Phosphonates discharged from wastewater treatment plants (WWTPs) have attracted increasing concerns because of their potential impact on eutrophication and potential risks to aquatic ecosystems. However, very few studies are available on their occurrence and transformation in WWTPs, partly due to the lack of sensitive methods for phosphonate analysis in complex matrices. Herein, based on our recent progress in phosphonate analysis, the occurrence and transformation of phosphonates along the full-scale wastewater treatment processes of two textile dyeing WWTPs were revealed. A set of typical phosphonates, including six phosphonate chelators (PCs) and four potential degradation products of PCs (DP-PCs) were quantified in different units and the final dewatered sludge. Three PCs (2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC), 1-hydroxyethane 1,1-diphosphonic acid (HEDP) and nitrilotris(methylene phosphonic acid) (NTMP)) at upmost mg/L and a considerable amount of four DP-PCs (9.12-608 μg/L) were detected in the influents of both WWTPs. In the subsequent treatment, NTMP could be removed more efficiently than PBTC and HEDP, especially in the coagulation unit, and the dissolved phosphonates were eliminated more readily than other dissolved organic phosphorus fractions. Of particular note, the toxicologically critical DP-PC (i.e., aminomethylphosphonic acid) was produced during the coagulation and biological treatment units. The final precipitation unit seemed essential to ensure satisfactory removal of PCs and DP-PCs. In addition, a significant accumulation of phosphonates in dewatered sludge (up to 7.81 g/kg) and the widespread occurrence of harmful DP-PCs also reminded us to pay more concerns on their potential risks during further sludge disposal in future.

The selected epigenetic effects of aminomethylphosphonic acid, a primary metabolite of glyphosate on human peripheral blood mononuclear cells (in vitro)

Aminomethylphosphonic acid (AMPA) is a primary metabolite of glyphosate and amino-polyphosphonate. We have determined the effect of AMPA on selected epigenetic parameters and major cell cycle drivers in human peripheral blood mononuclear cells (PBMCs). The cells were incubated with AMPA at 0.5, 10 and 250 μM for 24 h. The performed analysis included: global DNA methylation by colorimetric measurement of 5-methylcytosine in DNA, methylation in the promoter regions of selected tumor suppressor genes (P16, P21, TP53) and proto-oncogenes (BCL2, CCND1) as well as the expression profile of the indicated genes by Real-Time PCR assays. The obtained results have revealed significant reduction of global DNA methylation level in PBMCs exposed to AMPA. Investigated xenobiotic changed methylation pattern of the P21 and TP53 suppressor gene promoters, but in case of other analyzed genes: P16, BCL2 and CCND1 no statistically significant changes have been noted. Gene profiling have shown that AMPA only changed the expression of CCND1. Summing up, our results have revealed a small potential disturbance in methylation processes and the absence of changes in expression of tested tumor suppressor genes (P16, P21, TP53) and protooncogenes (BCL2) in human PBMCs exposed to AMPA.

Emerging contaminants in water used for maize irrigation: Economic and food safety losses associated with ciprofloxacin and glyphosate

Chemicals used to assure agricultural production and the feasibility of planting sites often end up in bodies of water used for crop irrigation. In a pot study, we investigated the consequences associated with the irrigation of maize with water contaminated by ciprofloxacin (Cipro; 0, 0.2, 0.8, 1.4 and 2.0 μg l-1) and/or glyphosate (0, 5, 25 and 50 mg l-1) on yields and food safety. Glyphosate in concentrations ≥25 mg l-1 prevented plant establishment, regardless of Cipro presence. Evaluations made at the V5 stage of plants reveal that Cipro concentrations ≥0.8 μg l-1 and glyphosate decreased photosynthesis and induced changes in leaf anatomy and stem biophysical properties that may contribute to decreased kernel yields. When those chemicals were applied together, kernel yield reductions were accentuated, evidencing their interactive effects. Irrigation with contaminated water resulted in accumulations of Cipro and glyphosate (as well as its metabolite, aminomethylphosphonic acid) in plant tissues. Accumulation of these chemicals in plant tissues such as leaves and kernels is a problem, since they are used to feed animals and humans. Moreover, these chemicals are of potential toxicological concern, principally due to residue accumulations in the food chain. Specially, the antibiotic residue accumulations in maize tissues can assist the induction of antibiotic resistance in dangerous bacteria. Therefore, we point out the urgency of monitoring the quality of water used for crop irrigation to avoid economic and food-quality losses.

Simultaneous and direct determination of glyphosate and AMPA in water samples from the hydroponic cultivation of eucalyptus seedlings using HPLC-ICP-MS/MS

Glyphosate is the main herbicide currently used in the world due to wide applicability and efficiency in controlling weeds in many crops. However, its overuse may lead to undesirable impacts on the environment and to human health in the long run. This present study aimed to optimize and validate solid phase extraction (SPE) using an anionic resin for the simultaneous and direct determination of glyphosate and aminomethylphosphonic acid (AMPA) in water samples using high-performance liquid chromatography combined with inductively coupled plasma with triple quadrupole mass spectrometer (HPLC-ICP-MS/MS). The results showed that recovery percentage and relative standard deviation were 103.9 ± 7.9 and 99.40 ± 9.9% for glyphosate and AMPA, respectively. The validation certified that the method was precise, accurate, linear, and selective, with a limit of quantification of 1.09 and 0.29 μg L-1 for glyphosate and AMPA, respectively. The optimized methodology reached the concentration factor of 250 times and was successfully applied to analyze water samples from hydroponic cultivation of the eucalyptus seedlings. The results showed that the exudation process occurs at glyphosate doses starting from 2 L ha-1.

Honeybee and consumer's exposure and risk characterisation to glyphosate-based herbicide (GBH) and its degradation product (AMPA): Residues in beebread, wax, and honey

In order to assess bee and human exposure to residues of glyphosate-based herbicide (GBH) and its main degradation products aminomethylphosphonic acid (AMPA) and to characterise the risk posed by these substances, we analysed 3 different bee matrices; beebread (N = 81), wax (N = 100) and 10-paired samples of wax/honey collected in 2016/2017 from 379 Belgian apiaries. A high-performance liquid chromatography-electrospray ionisation tandem mass spectrometry (HPLC-ESI-MS-MS) was used as analytical method. Limit of quantification and detection (LOQ and LOD) for GBH residues and AMPA in the 3 matrices was respectively of 10 ng g-1 and 1 ng g-1. In beebread, 81.5% of the samples showed a residue concentration > LOQ and 9.9% of the samples a residue concentration < LOQ (detection without quantification); no significant difference in detection rate was found between the north and the south of the country. Glyphosate was detected in beeswax less frequently than in beebread (i.e. 26% >LOQ versus 81.5% >LOQ). The maximum GBH residues and AMPA concentration found in beebread (respectively 700 ng g-1 and 250 ng g-1) led to sub-lethal exposure to bees. The Hazard Quotient (HQ) for beebread and beeswax (7 and 3.2, respectively) were far below the "safety" oral and contact thresholds for bees. For human health, the highest exposure to GBH residues in pollen corresponded to 0.312% and 0.187% of the ADI and of the ARfD respectively and, to 0.002% and to 0.001% for beeswax. No transfer of glyphosate from wax to honey was detected. Considering our results and the available regulatory data on the glyphosate molecule considered solely, not including the adjuvants in GBH formulation, the consumption of these three contaminated matrices would not be a food safety issue. Nonetheless, caution should be taken in the interpretation of the results as new studies indicate possible glyphosate/GBH residues toxicity below regulatory limits and at chronic sub-lethal doses.

Robust and highly sensitive micro liquid chromatography-tandem mass spectrometry method for analyses of polar pesticides (glyphosate, aminomethylphosfonic acid, N-acetyl glyphosate and N-acetyl aminomethylphosfonic acid) in multiple biological matrices

Glyphosate is the most used herbicide in agriculture. To monitor glyphosate exposure, analytical methods have to fulfill requirements with regard to sensitivity, reproducibility, ease of handling/high-throughput and applicability to multiple biological matrices. Furthermore, the methods have to include the degradation product of glyphosate, aminomethylphosfonic acid (AMPA) and preferably metabolites of glyphosate and AMPA, N-acetyl AMPA and N-acetyl glyphosate. Majority of the published methods for glyphosate and AMPA require derivatization to be able to achieve high sensitivity. In this work, we present highly sensitive microLC-MS/MS method for simultaneous quantification of glyphosate, AMPA, N-acetyl AMPA and N-acetyl glyphosate in multiple biological matrices without derivatization. The combination of simple sample clean-up procedures for simultaneous handling of 96 sample and short chromatographic run of only 3.4 min, meets the requirements for high-throughput methods. Simple mobile phase of water containing formic and medronic acids and isocratic run provided robust chromatographic separation on hypercarb column. The use of micro-flow system decreased the background noise, increasing the sensitivity. Achieved Low Limits of Quantification (LOQs) for liquid samples (plasma/serum/urine) were 0.00005 mg L-1 and 0.0001 mg kg-1 for solid samples (grain and soybean based feed/stomach/gizzard/intestinal content), which is more than 100 time more sensitive compared to QuPPe-Method. The method was validated in representative matrices with minimum of five fortification levels, six measurements per spiked concentration and three batches. All the samples were spiked with corresponding internal standards for all four analytes before sample clean-up procedures, ensuring high accuracy and precision. Recoveries for plasma/serum ranged between 86-108%, urine 93-120%, feed 91-115% and stomach/gizzard/intestinal content 92-110% with precision below 20%. The method's applicability was tested on 2000 samples measured during one year period.

Field-amplified sample injection and sweeping micellar electrokinetic chromatography in analysis of glyphosate and aminomethylphosphonic acid in wheat

Glyphosate, a widely used herbicide, has been classified as probably carcinogenic to humans by the International Agency for Research on Cancer (IARC). In the present study a method based on Field-Amplified Sample Injection and Sweeping Micellar Electrokinetic Chromatography (FASI sweep-MEKC) has been developed and validated for determination of glyphosate and its microbial metabolite aminomethylphosphonic acid (AMPA) in wheat flour. The method involved a preliminary solid phase extraction for cleanup of the aqueous extracts from wheat flour, based sequentially on C18 and strong anion exchange cartridges, followed by derivatization using 9-fluorenylmethylchloroformate. Optimization of sample cleanup and derivatization procedure was carried out by a HPLC-UV method, whereas FASI sweep-MEKC was applied for achieving the sensitivity necessary for analysis of real samples. To this regard, optimum conditions involved the use of an extended path fused-silica capillary (80 cm total length, 50 μm, i.d.) filled with a high concentration buffer (sodium phosphate 100 mM, pH 2.2). Electrokinetic sampling was carried out at -10 kV with injection time of 700 s and the separation of the loaded analytes was performed under MEKC conditions using sodium phosphate buffer 50 mM at pH 2.2, supplemented with sodium dodecyl sulfate, 100 mM. The method was validated for linearity, precision, accuracy and sensitivity, showing that using conventional UV detection (210 nm) the achieved limit of quantitation (LOQ) values for both the analytes were widely lower than those set by Authorities. In particular, LOQ for glyphosate and AMPA were found to be 5 and 2.5 ng/mL, respectively, corresponding to 0.1 and 0.05 mg/kg, in wheat flour. The method, applied to commercially available real samples (wheat flour from different manufacturers) and to an experimental sample obtained by cv. Svevo wheat, can be considered as a convenient alternative to the existing approaches in analysis of complex matrices.

Effects of aminomethylphosphonic acid, the main breakdown product of glyphosate, on cellular and biochemical parameters of the mussel Mytilus galloprovincialis

The effects of the breakdown products of herbicides on aquatic species are largely unknown. In a recent study, we evaluated the effects of glyphosate on the mussel Mytilus galloprovincialis. This study was designed to evaluate for the first time the impact of aminomethylphosphonic acid (AMPA) - the main breakdown product of glyphosate - on cellular and biochemical parameters of the mussel Mytilus galloprovincialis. Bivalves were exposed for 7, 14 and 21 days to 1, 10 and 100 μg/L of AMPA and various biomarkers were measured in haemolymph (total haemocyte counts, haemocyte diameter and volume, haemolymph pH, haemocyte proliferation, haemolymph lactate dehydrogenase activity, haemocyte lysate lysozyme and acid phosphatase activities), as well as in gills and digestive gland (superoxide dismutase, catalase, glutathione S-transferase and acetylcholinesterase activities). AMPA concentrations in seawater samples from the experimental tanks were also measured in order to correlate the biomarker responses of mussels with their exposure to the actual concentrations of AMPA. The MANOVA analysis demonstrated that the experimental variables considered (exposure dose, exposure duration, and their interaction) affected significantly biomarker responses. Nevertheless, the two-way ANOVA analysis revealed significant effects of AMPA on most of the biomarkers measured. The overall results of this study demonstrated that AMPA can affect cellular and biochemical parameters in mussels, similarly to glyphosate.

The different behaviors of glyphosate and AMPA in compost-amended soil

The broad-spectrum herbicide glyphosate is one of the most widely used pesticides. Both glyphosate and its major metabolite, aminomethylphosphonic acid (AMPA), persist in waters; thus, their environmental fates are of interest. We investigated the influence of compost dose, sampling depth, moisture and saturated hydraulic conductivity (Ks) on the persistence of these substances. The amounts of AMPA quantified by triple quadrupole liquid chromatography-mass spectrometry (LC-QqQ-MS/MS) using isotopically labeled extraction standards were higher than those of glyphosate and differed among the samples. Both glyphosate and AMPA showed gradually decreasing concentrations with soil depth, and bootstrapped ANOVA showed significant differences between the contents of glyphosate and AMPA and their behavior related to different compost dosages and sampling depths. However, the compost dose alone did not cause significant differences among samples. Bayesian statistics revealed that the amounts of glyphosate and AMPA were both dependent on the sampling depth and compost dose, but differences were found when considering the physical factors of Ks and moisture. Glyphosate was influenced by moisture but not Ks, whereas AMPA was influenced by Ks but not moisture. Importantly, we found behavioral differences between glyphosate and its major metabolite, AMPA, related to the physical properties of Ks and moisture.

Herbicides in river water across the northeastern Italy: occurrence and spatial patterns of glyphosate, aminomethylphosphonic acid, and glufosinate ammonium

Glyphosate and glufosinate ammonium are the active ingredients of commonly used herbicides. Active agricultural lands extend over a large part of the Veneto region (Eastern Po Valley, Italy) and glyphosate and glufosinate ammonium are widely used. Consequently, surface waters can be potentially contaminated. This study investigates the occurrence of glyphosate and glufosinate ammonium as well as aminomethylphosphonic acid (AMPA, the degradation product of glyphosate) in river water of Veneto. Eighty-six samples were collected in 2015 at multiple sampling points across the region. Samples were analyzed for the two target herbicides, AMPA as well as for other variables, including water temperature, pH, dissolved oxygen, conductivity, hardness, BOD, COD, inorganic ions, total nitrogen, total phosphorus, total suspended solids, arsenic, and lead. The average concentrations (all samples) were 0.17, 0.18, and 0.10 μg L-1 for glyphosate, AMPA, and glufosinate ammonium, respectively. The European upper tolerable level for pesticides (annual average 0.1 μg L-1) was often exceeded. Chemometric analysis was therefore applied to (i) investigate the relationships among water pollutants, (ii) detect the potential sources of water contamination, (iii) assess the effective water pollution of rivers by identifying river basins with anomalous pollution levels, and (iv) assess the spatial variability of detected sources. Factor analysis identified four factors interpreted as potential sources and processes (use of herbicides, leaching of fertilizers, urban/industrial discharges, and the biological activity on polluted or stagnant waters). A discriminant analysis revealed that the pollution from anthropogenic discharges is homogeneously present in surface water of Veneto, while biological activity and fertilizers present heterogeneous distributions. This study gives insights into the concentrations of herbicides in rivers flowing through a wide region that has heavy use of these chemicals in agriculture. The study also points out some hot-spots and suggests the future implementation of the current monitoring protocols and network.

Some aspects of the adsorption of glyphosate and its degradation products on montmorillonite

The most worldwide used herbicide is glyphosate, phosphonomethylglycine (PMG). Consequently, a significant amount of PMG, its metabolites (sarcosine, SAR, and aminomethylphosphonic acid, AMPA) and the degradation product, methylphosphonic acid (MPA), reaches the soil, which acts as final sink. Because clays are one of the most reactive components of soils, expansive clays such as montmorillonite (Mt) are used to retain agriculture contaminants with some success. In this work, as a preliminary step for the evaluation of the risk that PMG, SAR, AMPA, and MPA occurrence could have on the environment, their adsorption on Mt surface was performed. The adsorption process was analyzed at constant adsorbate concentrations and two pH values to take into account the different protonation states of the amino group. DTA, XRD, zeta potential measurements, and XPS were used to identify the interactions or association mechanisms with the clay surface, the entry of adsorbates into the Mt interlayer, and electric charge changes on the Mt surface, and evaluate the acid-base surface complex constants, respectively. The interlayer thickness in acid media indicated that adsorbates are able to enter the interlayer in planar form. Besides, for the Mt-PMG sample, some PMG molecules could be also inserted as a bilayer or with a tilt angle of 52.4° in the interlayer. However, in alkaline media, the interlayer thickness indicated that the adsorbate arrangement differed from that of acidic media where PMG and MPA could have more than one orientation. The surface complex deprotonation constants were determined for the =NH+2 ⇆ =NH+H+ process, being 3.0, 5.0, and 7.3 for PMG, AMPA, and SAR, respectively.

Recent advances in glyphosate biodegradation

Glyphosate has emerged as the most widespread herbicide to control annual and perennial weeds. Massive use of glyphosate for decades has resulted in its ubiquitous presence in the environment, and poses a threat to humans and ecosystem. Different approaches such as adsorption, photocatalytic degradation, and microbial degradation have been studied to break down glyphosate in the environment. Among these, microbial degradation is the most effective and eco-friendly method. During its degradation, various microorganisms can use glyphosate as a sole source of phosphorus, carbon, and nitrogen. Major glyphosate degradation pathways and its metabolites have been frequently investigated, but the related enzymes and genes have been rarely studied. There are many reviews about the toxicity and fate of glyphosate and its major metabolite, aminomethylphosphonic acid. However, there is lack of reviews on biodegradation and bioremediation of glyphosate. The aims of this review are to summarize the microbial degradation of glyphosate and discuss the potential of glyphosate-degrading microorganisms to bioremediate glyphosate-contaminated environments. This review will provide an instructive direction to apply glyphosate-degrading microorganisms in the environment for bioremediation.

Persistence of glyphosate and aminomethylphosphonic acid in loess soil under different combinations of temperature, soil moisture and light/darkness

The dissipation kinetics of glyphosate and its metabolite aminomethylphosphonic acid (AMPA) were studied in loess soil, under biotic and abiotic conditions, as affected by temperature, soil moisture (SM) and light/darkness. Nonsterile and sterile soil samples were spiked with 16mgkg-1 of glyphosate, subjected to three SM contents (20% WHC, 60% WHC, saturation), and incubated for 30days at 5°C and 30°C, under dark and light regimes. Glyphosate and AMPA dissipation kinetics were fit to single-first-order (SFO) or first-order-multicompartment (FOMC) models, per treatment combination. AMPA kinetic model included both the formation and decline phases. Glyphosate dissipation kinetics followed SFO at 5°C, but FOMC at 30°C. AMPA followed SFO dissipation kinetics for all treatments. Glyphosate and AMPA dissipation occurred mostly by microbial activity. Abiotic processes played a negligible role for both compounds. Under biotic conditions, glyphosate dissipation and AMPA formation/dissipation were primarily affected by temperature, but also by SM. Light regimes didn't play a significant role. Glyphosate DT50 varied between 1.5 and 53.5days, while its DT90 varied between 8.0 and 280days, depending on the treatment. AMPA persisted longer in soil than glyphosate, with its DT50 at 30°C ranging between 26.4 and 44.5days, and its DT90 between 87.8 and 148days. The shortest DT50/DT90 values for both compounds occurred at 30°C and under optimal/saturated moisture conditions, while the largest occurred at 5°C and reaching drought stress conditions. Based on these results, we conclude that glyphosate and AMPA dissipate rapidly under warm and rainy climate conditions. However, repeated glyphosate applications in fallows or winter crops in countries where cold and dry winters normally occur could lead to on-site soil pollution, with consequent potential risks to the environment and human health. To our knowledge, this study is the first evaluating the combined effect of temperature, soil moisture and light/dark conditions on AMPA formation/dissipation kinetics and behaviour.

A simple method for the determination of glyphosate and aminomethylphosphonic acid in seawater matrix with high performance liquid chromatography and fluorescence detection

Glyphosate (GLYP) is an important herbicide which is also used as the phosphorus source for marine organisms. The wide applications of GLYP can lead to its accumulation in oceans and coastal waters, thus creating environmental issues. However, there is limited methods for detection of GLYP and its degradation product, aminomethylphosphonic acid (AMPA) in saline samples. Therefore, a simple and fast method for the quantification of GLYP and AMPA in seawater matrix has been developed based on the derivatization with 9-fluorenylmethylchloroformate (FMOC-Cl), separation with high performance liquid chromatography (HPLC) and detection with fluorescence detector (FLD). In order to maximize sensitivity, the derivatization procedure was carefully optimized regarding concentration of FMOC-Cl, volume of borate buffer, pH of borate buffer, mixing and derivatization time. The derivatization reaction could be completed within 30min in seawater samples without any additional clean-up or desalting steps. Under the optimized conditions, the developed HPLC method showed a wide linear response (up to several mg/L, R2>0.99). The limits of detection were 0.60μg/L and 0.30μg/L for GLYP and AMPA in seawater matrix, respectively. The relative standard deviation was 14.0% for GLYP (1.00mg/L) and 3.1% for AMPA (100μg/L) in saline samples with three different operators (n=24). This method was applied to determine the concentration of GLYP and AMPA in seawater culture media and the recovery data indicated minimal matrix interference. Due to its simplicity, high reproducibility and successful application in seawater culture media analysis, this method is a potentially useful analytical technique for both marine research and environmental science.

Glyphosate and aminomethylphosphonic acid chronic risk assessment for soil biota

Glyphosate is a broad-spectrum herbicide used widely in agriculture, horticulture, private gardens, and public infrastructure, where it is applied to areas such as roadsides, railway tracks, and parks to control the growth of weeds. The exposure risk from glyphosate and the primary soil metabolite aminomethylphosphonic acid (AMPA) on representative species of earthworms, springtails, and predatory soil mites and the effects on nitrogen-transformation processes by soil microorganisms were assessed under laboratory conditions based on internationally recognized guidelines. For earthworms, the reproductive no-observed-effect concentration (NOEC) was 472.8 mg glyphosate acid equivalent (a.e.)/kg dry soil, which was the highest concentration tested, and 198.1 mg/kg dry soil for AMPA. For predatory mites, the reproductive NOEC was 472.8 mg a.e./kg dry soil for glyphosate and 320 mg/kg dry soil for AMPA, the highest concentrations tested. For springtails, the reproductive NOEC was 472.8 mg a.e./kg dry soil for glyphosate and 315 mg/kg dry soil for AMPA, the highest concentrations tested. Soil nitrogen-transformation processes were unaffected by glyphosate and AMPA at 33.1 mg a.e./kg soil and 160 mg/kg soil, respectively. Comparison of these endpoints with worst-case soil concentrations expected for glyphosate (6.62 mg a.e./kg dry soil) and AMPA (6.18 mg/kg dry soil) for annual applications at the highest annual rate of 4.32 kg a.e./ha indicate very low likelihood of adverse effects on soil biota. Environ Toxicol Chem 2016;35:2742-2752. © 2016 The Authors. Environmental Toxicology and Chemistry Published by Wiley Periodicals, Inc. on behalf of SETAC.

Aminomethylphosphonic acid has low chronic toxicity to Daphnia magna and Pimephales promelas

Aminomethylphosphonic acid (AMPA) is the simplest member of a class of compounds known as aminomethylenephosphonates and the only environmental metabolite measured in significant amounts during the degradation of the herbicide glyphosate in soil. However, there are additional sources of AMPA in the environment, originating from organic phosphonates which are used in water treatment to inhibit scale formation and corrosion. Like glyphosate, AMPA has low acute toxicity to aquatic animals, and the no-observed-adverse effect concentration (NOAEC) obtained from a fish full-life cycle study for glyphosate was determined to be 26 mg/L. However, the chronic toxicity of AMPA to aquatic animals has not been evaluated before. The purpose of the present study was to assess the potential for chronic toxicity of AMPA to fathead minnow (Pimephales promelas) and Daphnia magna. Chronic toxicity to P. promelas was evaluated in a fish early-life stage study. The primary endpoints were larval survival, growth, and development. The NOAEC for P. promelas was determined to be 12 mg/L, the highest concentration tested. The chronic toxicity to D. magna was evaluated in a Daphnia reproduction test. The primary endpoints were survival, growth, and reproduction. The no-observed-effect concentration for D. magna was determined to be 15 mg/L. Conservatively predicted environmental surface water concentrations for AMPA from typical foliar agricultural application rates and values from surface water monitoring programs are 100 to 1000 times less than the NOAEC values from both studies. Consequently, there is a large and highly protective margin of safety between realistic environmental exposures to AMPA and chronic toxicity to aquatic vertebrates and invertebrates.

Determination of glyphosate and aminomethylphosphonic acid in aqueous soil matrices: a critical analysis of the 9-fluorenylmethyl chloroformate derivatization reaction and application to adsorption studies

The assessment of the environmental fate of glyphosate and its degradation product (aminomethylphosphonic acid) is of great interest given the widespread use of the herbicide. Studies of adsorption-desorption and transport processes in soils require analytical methods with sensitivity, accuracy, and precision suitable for determining the analytes in aqueous equilibrium solutions of varied complexity. In this work, the effect of factors on the yield of the derivatization of both compounds with 9-fluorenylmethyl chloroformate for applying in aqueous solutions derived from soils was evaluated through factorial experimental designs. Interference effects coming from background electrolytes and soil matrices were established. The whole method had a linear response up to 640 ng/mL (R(2) > 0.999) under optimized conditions for high-performance liquid chromatography with fluorescence detection. Limits of detection were 0.6 and 0.4 ng/mL for glyphosate and aminomethylphosphonic acid, respectively. The relative standard deviation was 4.4% for glyphosate (20 ng/mL) and 5.9% for aminomethylphosphonic acid (10 ng/mL). Adsorption of compounds on four different soils was assessed. Isotherm data fitted well the Freundlich model (R(2) > 0.97). Kf constants varied between 93 ± 3.1 and 2045 ± 157 for glyphosate and between 99 ± 4.1 and 1517 ± 56 (μg(1-1/) (n)  mL(1/) (n) ( ) g(-1) ) for aminomethylphosphonic acid, showing the broad range of applicability of the proposed method.

Alteration of plant physiology by glyphosate and its by-product aminomethylphosphonic acid: an overview

It is generally claimed that glyphosate kills undesired plants by affecting the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) enzyme, disturbing the shikimate pathway. However, the mechanisms leading to plant death may also be related to secondary or indirect effects of glyphosate on plant physiology. Moreover, some plants can metabolize glyphosate to aminomethylphosphonic acid (AMPA) or be exposed to AMPA from different environmental matrices. AMPA is a recognized phytotoxin, and its co-occurrence with glyphosate could modify the effects of glyphosate on plant physiology. The present review provides an overall picture of alterations of plant physiology caused by environmental exposure to glyphosate and its metabolite AMPA, and summarizes their effects on several physiological processes. It particularly focuses on photosynthesis, from photochemical events to C assimilation and translocation, as well as oxidative stress. The effects of glyphosate and AMPA on several plant physiological processes have been linked, with the aim of better understanding their phytotoxicity and glyphosate herbicidal effects.

Dynamics and environmental risk assessment of the herbicide glyphosate and its metabolite AMPA in a small vineyard river of the Lake Geneva catchment

The use of pesticides may lead to environmental problems, such as surface water pollution, with a risk for aquatic organisms. In the present study, a typical vineyard river of western Switzerland was first monitored to measure discharged loads, identify sources, and assess the dynamic of the herbicide glyphosate and its metabolite aminomethylphosphonic acid (AMPA). Second, based on river concentrations, an associated environmental risk was calculated using laboratory tests and ecotoxicity data from the literature. Measured concentrations confirmed the mobility of these molecules with elevated peaks during flood events, up to 4970 ng/L. From April 2011 to September 2011, a total load of 7.1 kg was calculated, with 85% coming from vineyards and minor urban sources and 15% from arable crops. Compared with the existing literature, this load represents an important fraction (6-12%) of the estimated amount applied because of the steep vineyard slopes (∼10%). The associated risk of these compounds toward aquatic species was found to be negligible in the present study, as well as for other rivers in Switzerland. A growth stimulation was nevertheless observed for the algae Scenedesmus vacuolatus with low concentrations of glyphosate, which could indicate a risk of perturbation in aquatic ecosystems, such as eutrophication. The combination of field and ecotoxicity data allowed the performance of a realistic risk assessment for glyphosate and AMPA, which should be applied to other pesticide molecules.

Questions concerning the potential impact of glyphosate-based herbicides on amphibians

Use of glyphosate-based herbicides is increasing worldwide. The authors review the available data related to potential impacts of these herbicides on amphibians and conduct a qualitative meta-analysis. Because little is known about environmental concentrations of glyphosate in amphibian habitats and virtually nothing is known about environmental concentrations of the substances added to the herbicide formulations that mainly contribute to adverse effects, glyphosate levels can only be seen as approximations for contamination with glyphosate-based herbicides. The impact on amphibians depends on the herbicide formulation, with different sensitivity of taxa and life stages. Effects on development of larvae apparently are the most sensitive endpoints to study. As with other contaminants, costressors mainly increase adverse effects. If and how glyphosate-based herbicides and other pesticides contribute to amphibian decline is not answerable yet due to missing data on how natural populations are affected. Amphibian risk assessment can only be conducted case-specifically, with consideration of the particular herbicide formulation. The authors recommend better monitoring of both amphibian populations and contamination of habitats with glyphosate-based herbicides, not just glyphosate, and suggest including amphibians in standardized test batteries to study at least dermal administration.