Aminomethylphosphonic acid alters amphibian embryonic development at environmental concentrations

Gestational glyphosate exposure and early childhood neurodevelopment in a Puerto Rico birth cohort

INTRODUCTION

N-(phosphonomethyl)glycine, or glyphosate, is a non-selective systemic herbicide widely used in agricultural, industrial, and residential settings since 1974. Glyphosate exposure has been inconsistently linked to neurotoxicity in animals, and studies of effects of gestational exposure among humans are scarce. In this study we investigated relationships between prenatal urinary glyphosate analytes and early childhood neurodevelopment.

METHODS

Mother-child pairs from the PROTECT-CRECE birth cohort in Puerto Rico with measures for both maternal urinary glyphosate analytes and child neurodevelopment were included for analysis (n = 143). Spot urine samples were collected 1-3 times throughout pregnancy and analyzed for glyphosate and aminomethylphosphonic acid (AMPA), an environmental degradant of glyphosate. Child neurodevelopment was assessed at 6, 12, and 24 months using the Battelle Developmental Inventory, 2nd edition Spanish (BDI-2), which provides scores for adaptive, personal-social, communication, motor, and cognitive domains. We used multivariable linear regression to examine associations between the geometric mean of maternal urinary glyphosate analytes across pregnancy and BDI-2 scores at each follow-up. Results were expressed as percent change in BDI-2 score per interquartile range increase in exposure.

RESULTS

Prenatal AMPA concentrations were negatively associated with communication domain at 12 months (%change = -5.32; 95%CI: 9.04, -1.61; p = 0.007), and communication subdomain scores at 12 and 24 months. At 24 months, four BDI-2 domains were associated with AMPA: adaptive (%change = -3.15; 95%CI: 6.05, -0.25; p = 0.038), personal-social (%change = -4.37; 95%CI: 7.48, -1.26; p = 0.008), communication (%change = -7.00; 95%CI: 11.75, -2.26; p = 0.005), and cognitive (%change = -4.02; 95%CI: 6.72, -1.32; p = 0.005). Similar trends were observed with GLY concentrations, but most confidence intervals include zero. We found no significant associations at 6 months.

CONCLUSIONS

Our results suggest that gestational exposure to glyphosate is associated with adverse early neurodevelopment, with more pronounced delays at 24 months. Given glyphosate's wide usage, further investigation into the impact of gestational glyphosate exposure on neurodevelopment is warranted.

Exposure to Low Concentrations of AMPA Influences Morphology and Decreases Survival During Larval Development in a Widespread Amphibian Species

Glyphosate's primary metabolite, AMPA (aminomethylphosphonic acid), is one of the most widely detected anthropogenic substance in surface waters worldwide. However, ecotoxicological studies on the potential effects of this metabolite at environmental concentrations on wildlife are scarce. Yet, due to its chemical properties, AMPA is likely to affect non-target species. In this study, we investigated sublethal effects of environmental concentrations of AMPA on the larval development of a widespread amphibian species, the spined toad Bufo spinosus. We performed a factorial experiment to study the effect of concentration and the timing of exposure (during embryonic development, larval development or both) to AMPA on the morphology, rate of development and survival of tadpoles. AMPA and timing of exposure interactively affected tadpole size (individuals exposed to AMPA after hatching were transitorily smaller, while individuals exposed to AMPA before hatching were longer), but not duration of development. Most of these effects were linked to exposure during embryonic development. Such effects in individuals exposed during embryonic development solely were long-lasting and persisted until the latest larval stages. Finally, we found that exposure to AMPA after hatching (during the larval stage) increased mortality. Exposure to low environmental concentrations of AMPA could have long-lasting consequences on fitness and population persistence. These findings are especially important to take into account at a time when multiple threats can interact to affect wildlife.

Direct, automated and sensitive determination of glyphosate and related anionic pesticides in environmental water samples using solid-phase extraction on-line combined with liquid chromatography tandem mass spectrometry

An automated procedure for the simultaneous determination of six anionic pesticides, including glyphosate (GLY) and its transformation product aminomethylphosphonic acid (AMPA), was developed and applied to the analysis of environmental water samples. The proposed method combines on-line concentration of water samples (0.160 mL), with compounds separation in an anion-exchange liquid chromatography (LC) column, followed by their selective determination by tandem mass spectrometry (MS/MS). The global procedure was completed in 25 min, providing limits of quantification (LOQs) between 5 ng L^-1 and 20 ng L^-1, with reduced effect of the surface water matrix in the efficiency of process (SPE and ionization yields). The method was applied to the analysis of grab samples obtained from three watersheds, in two rural and one residential area, in Galicia (Northwest Spain). Out of six investigated compounds, Fosetyl, AMPA and GLY were noticed in the set of processed samples. Their detection frequencies increased from 12% (Fosetyl) to 88% (AMPA). Median concentrations followed the same trend varying from 9 ng L^-1 (Fosetyl) to 44 ng L^-1 (AMPA). The higher levels and the large seasonal variations in the residues of the latter species were noticed in small rivers affected by discharges of municipal sewage treatment plants (STPs).

Exposure, but not timing of exposure, to a sulfonylurea herbicide alters larval development and behaviour in an amphibian species

Environmental contamination is one of the major causes of biodiversity loss. Wetlands are particularly susceptible to contamination and species inhabiting these habitats are subjected to pollutants during sensitive phases of their development. In this study, tadpoles of a widespread amphibian, the spined toad (Bufo spinosus), were exposed to environmental concentrations of nicosulfuron (0 μg/L; 0.15 ± 0.05 μg/L and 0.83 ± 0.04 μg/L), a sulfonylurea herbicide, during different phases of development. Tadpoles were exposed during embryonic (12.98 ± 0.90 days) or larval development (93.74± 0.85 days), or throughout both phases, and we quantified development duration, morphological traits and behavioural features as responses to exposure. Developing tadpoles exposed to nicosulfuron were larger, but with smaller body, and had shorter but wider tail muscles. They were also more active and swam faster than control tadpoles and showed diverging patterns of behavioural complexity. We showed that higher concentrations had greater effects on individuals than lower concentrations, but the timing of nicosulfuron exposure did not influence the metrics studied: Exposure to nicosulfuron triggered similar effects irrespective of the developmental stages at which exposure occurred. These results further indicate that transient exposure (e.g., during embryonic development) can induce long-lasting effects throughout larval development to metamorphosis. Our study confirms that contaminants at environmental concentrations can have strong consequences on non-target organisms. Our results emphasize the need for regulation agencies and policy makers to consider sublethal concentrations of sulfonulyrea herbicides, such as nicosulfuron, as a minimum threshold in their recommendations.

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.

Did decades of glyphosate use have selected for resistant amphibians in agricultural habitats?

Glyphosate-based herbicides are used worldwide, and glyphosate's primary metabolite (aminomethylphosphonic acid: AMPA), is globally retrieved in surface waters. AMPA induces various adverse effects on aquatic wildlife, including selective mortality, which suggests that glyphosate exposure may have selected for AMPA-resistant individuals. We tested this hypothesis using spined toads (Bufo spinosus), an amphibian found in a variety of habitats, from AMPA-exposed agricultural lands to AMPA-free forested areas. We predicted that the offspring of individuals originating from agricultural habitats would develop AMPA-resistance - and be less prone to develop adverse effects from- AMPA exposure. To investigate this question, we performed a common garden brood-rearing experiment. The embryos and larvae of 40 spined toad pairs captured in agricultural and forest ponds were exposed either to an environmental relevant concentration of AMPA (0.4 μg L^-1) or to control conditions (n = 8160 embryos, n = 240 tadpoles). We monitored development durations, developmental abnormalities and morphology, measured across key developmental stages. Although we observed significant effects of AMPA on fitness parameters in each group, these effects were not exacerbated in individuals from AMPA-free habitats. We suggest that temporal and/or spatial dynamics of contamination, as well as gene flow between exposed and preserved populations, may hinder adaptive divergence between populations. Yet, we show strong adverse effects of AMPA exposure at early developmental stages. AMPA could therefore be one of the numerous causes of declining wild amphibian populations.

Association of Glyphosate Exposure with Blood DNA Methylation in a Cross-Sectional Study of Postmenopausal Women

BACKGROUND

Glyphosate is the most commonly used herbicide in the world and is purported to have a variety of health effects, including endocrine disruption and an elevated risk of several types of cancer. Blood DNA methylation has been shown to be associated with many other environmental exposures, but to our knowledge, no studies to date have examined the association between blood DNA methylation and glyphosate exposure.

OBJECTIVE

We conducted an epigenome-wide association study to identify DNA methylation loci associated with urinary glyphosate and its metabolite aminomethylphosphonic acid (AMPA) levels. Secondary goals were to determine the association of epigenetic age acceleration with glyphosate and AMPA and develop blood DNA methylation indices to predict urinary glyphosate and AMPA levels.

METHODS

For 392 postmenopausal women, white blood cell DNA methylation was measured using the Illumina Infinium MethylationEPIC BeadChip array. Glyphosate and AMPA were measured in two urine samples per participant using liquid chromatography-tandem mass spectrometry. Methylation differences at the probe and regional level associated with glyphosate and AMPA levels were assessed using a resampling-based approach. Probes and regions that had an false discovery rate q < 0.1 in ≥ 90 % of 1,000 subsamples of the study population were considered differentially methylated. Differentially methylated sites from the probe-specific analysis were combined into a methylation index. Epigenetic age acceleration from three epigenetic clocks and an epigenetic measure of pace of aging were examined for associations with glyphosate and AMPA.

RESULTS

We identified 24 CpG sites whose methylation level was associated with urinary glyphosate concentration and two associated with AMPA. Four regions, within the promoters of the MSH4, KCNA6, ABAT, and NDUFAF2/ERCC8 genes, were associated with glyphosate levels, along with an association between ESR1 promoter hypomethylation and AMPA. The methylation index accurately predicted glyphosate levels in an internal validation cohort. AMPA, but not glyphosate, was associated with greater epigenetic age acceleration.

DISCUSSION

Glyphosate and AMPA exposure were associated with DNA methylation differences that could promote the development of cancer and other diseases. Further studies are warranted to replicate our results, determine the functional impact of glyphosate- and AMPA-associated differential DNA methylation, and further explore whether DNA methylation could serve as a biomarker of glyphosate exposure. https://doi.org/10.1289/EHP10174.

Glyphosate vs. Glyphosate-Based Herbicides Exposure: A Review on Their Toxicity

Glyphosate-based herbicide has been the first choice for weed management worldwide since the 1970s, mainly due to its efficacy and reported low toxicity, which contributed to its high acceptance. Many of the recent studies focus solely on the persistence of pesticides in soils, air, water or food products, or even on the degree of exposure of animals, since their potential hazards to human health have raised concerns. Given the unaware exposure of the general population to pesticides, and the absence of a significant number of studies on occupational hazards, new glyphosate-induced toxicity data obtained for both residual and acute doses should be analyzed and systematized. Additionally, recent studies also highlight the persistence and toxicity of both glyphosate metabolites and surfactants present in herbicide formulations. To renew or ban the use of glyphosate, recently published studies must be taken into account, aiming to define new levels of safety for exposure to herbicide, its metabolites, and the toxic excipients of its formulations. This review aims to provide an overview of recent publications (2010–present) on in vitro and in vivo studies aimed at verifying the animal toxicity induced by glyphosate, its metabolite aminomethylphosphonic acid (AMPA) and glyphosate-based formulations, evaluated in various experimental models. Apart from glyphosate-induced toxicity, recent data concerning the role of surfactants in the toxicity of glyphosate-based formulations are discussed.

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.