13
Nov
Glyphosate Mixtures Show Lethal and Sublethal Effects to Embryos, Highlights Regulatory Deficiencies
(Beyond Pesticides, November 13, 2024) A study in Chemosphere, conducted by researchers from the Institute of Biochemistry and Molecular Biology in Germany, reveals the varied lethal and sublethal effects of different glyphosate mixtures through tests on the South African clawed frog, Xenopus laevis (X. laevis). After exposing embryos to four glyphosate formulations, mortality, morphological defects, altered heartbeat rate, and impaired heart-specific gene expression are observed. Glyphosate, an herbicide and popular weed killer in many Roundup® products, is one of the most commonly detected pesticides in waterbodies worldwide, threatening aquatic organisms and overall biodiversity.
This study investigates the effects of Glyphosat TF, Durano TF, Helosate 450 TF, and Kyleo, four formulations containing glyphosate, as compared to the effects of pure glyphosate on embryonic development in amphibians. The formulations consist of varying concentrations of the active ingredient glyphosate, as well as other active and inert ingredients. The authors share that, “Glyphosat TF contains 34% glyphosate and 10–20% d-glucopyranose, while Durano contains 39–44% glyphosate and 1–5% N–N-dimethyl-C12-C14-(even numbered)-alkyl-1-amines. In Helosate most of the ingredients are listed – 50–70% glyphosate, 1–10% isopropylamine, 1–3% lauryl dimethyl betaine, 0.25–1% dodecyl dimethylamine. Kyleo only lists the active ingredients glyphosate (27.9%) and 2,4-D (32%).â€
2-cell stage embryos (early stage of embryonic development) were utilized as the exposure start point to assess embryo developmental effects within the pesticide solutions. All solutions were prepared with glyphosate concentrations of 0.01, 0.1, 1, 10, and 100 mg/L. “The exposure of embryos to 0.01–10 mg/L glyphosate reflects environmentally relevant concentrations already measured in different countries, with 100 mg/L glyphosate representing ‘worst-case’ scenarios (e.g., incorrect handling or improper disposal), but already measured in water bodies in Argentina,†the researchers state.
Embryos were observed for death every 30 minutes for the first two hours after the start of exposure, and then every 24 hours until they reached stage 44/45. Surviving organisms were analyzed for their general morphological phenotype and potential developmental retardation, as well as embryo mobility, heart rate measurements, immunostaining of the heart, brain and heart measurements, gene expression analysis, and cell apoptosis.
Lethal effects are seen with many of the formulations during the first few days of exposure. “100% embryo mortality was detected after four days (NF-stage 30) of exposure to 100 mg/L glyphosate in Durano,†the authors note. Three days of exposure to 100 mg/L glyphosate in Helosate also shows 100% mortality. Embryos exposed to Kyleo have the most severe lethal effects, as “exposure to Kyleo containing 100 mg/L glyphosate caused 100% mortality within two days (NF-stage 15), while even at 10 mg/L Kyleo exposure led to 96% mortality after five days (NF-stage 33/34).†Â
In the surviving organisms, the formulations result in malformations such as reduced eye and head size. These sublethal concentrations are also linked to impaired heart morphology and function, as well as altered expression of heart-specific genes. As compared to the control group, a reduction of the embryos’ heart rate after exposure to all four glyphosate formulations is also seen.
Expression of key cardiogenic genes (mhcα, mef2d, and tnni3) aids in heart muscle cell differentiation and is critical for development. In exposing embryos to each of the four formulations, expression intensity and area were altered for these genes. The researchers report, “[E]xposure to Durano (0.1 mg/L glyphosate) increased the intensity of mhcα expression… Exposure to 0.1 mg/L glyphosate in Helosate led to an increase in the area and intensity of mhcα expression.â€
Exposure to 0.1 mg/L glyphosate in both Glyphosat TF and Kyleo led to reduced intensity of mef2d expression. “Helosate (0.1 mg/L glyphosate), on the other hand, resulted in an increase in mef2d expression intensity,†the authors say. The gene tnni3 showed a reduced expression intensity with 0.1 mg/L glyphosate in both Glyphosat TF and Helosate, and helosate exposure also led to an increase in apoptotic cells with the embryos. A study in 2022 has shown that glyphosate and glyphosate-based herbicides (GBH) like Roundup® induce DNA damage and alter biological mechanisms (gene regulatory microRNAs [miRNAs or miRs]) associated with cancer development (See more on altered genes here.)
“Exposure to glyphosate-based herbicides investigated in present study altered the expression levels (area and intensity) of the genes mhcα, mef2d and tnni3 to varying degrees depending on the specific formulation,†the researchers find. “Despite the differences in gene expression among formulations, all showed significant deviations from control embryos, confirming that these formulations disrupt cardiac differentiation in X. laevis embryos.†Altering the embryos of X. laevis down to a molecular level shows the adverse effects of glyphosate and its formulations on key species that can ripple throughout the ecosystem.
“The present study confirmed that glyphosate formulations can have both lethal and sublethal effects on X. laevis embryos. The different formulations selected for exposure experiments showed varying degrees of lethal effects at the same concentrations of the active ingredient glyphosate,†the researchers summarize. With the varied results, the authors hypothesize that the other ingredients play a role in toxicity. “The high lethal effect of the Kyleo formulation (starting at 10 mg/L glyphosate) may be due to the addition of the second active ingredient 2,4-D as this herbicidal active ingredient mimics the plant growth hormone auxin and overstimulates cell division leading to plant death,†they postulate. “[W]e attribute the high mortality observed with Kyleo primarily to a combination effect of different ingredients (glyphosate, 2,4-D, and other ingredients) in the formulation and not to glyphosate alone.â€
Currently, the U.S. Environmental Protection Agency (EPA) performs risk assessments on individual active ingredients, ignoring the potential synergistic effects of pesticide mixtures. Beyond Pesticides has long documented how synergy should be included in all pesticide registration processes, as well as the regulatory failures of EPA. (See more here and here.)
This study confirms that glyphosate formulations have a stronger effect on X. laevis embryogenesis than pure glyphosate, leading the authors to conclude that “it is crucial to evaluate the active ingredient and the co-formulations independently, as well as the combined, commercially available products, during pesticide risk assessments and renewal procedures of agrochemicals. The severe global decline of amphibians, partly due to herbicide use, highlights the need for strict and efficient monitoring of environmental pesticide loads and application areas.†(See previous coverage here.)
Formulations containing glyphosate as the active ingredient also incorporate other, often undisclosed, co-formulants. These additional components could alter or intensify the toxicity towards organisms like X. laevis. “To date, the herbicide glyphosate and its various formulations have been widely studied in laboratory, driven by the increasing concerns over their unanticipated effects on a wide range of non-target organisms (from soil microbes to vertebrates) and their potential risks they pose to human health,†the researchers emphasize. “Nevertheless, uncertainties remain regarding their toxicity and effects on aquatic non-target organisms.â€
These uncertainties are threatening the health of all organisms, as well as the stability of both aquatic and terrestrial food webs. This study “highlights the importance of evaluating not only the active ingredients but also their combinations in formulations before new authorizations or renewals are granted,†the researchers note. “Given the substantial variation in lethal concentrations across different amphibian species, it is crucial to investigate the effects of herbicides, and more generally pesticides, across a diverse range of taxa to safeguard wildlife and ecosystem stability.â€
Biodiversity loss is one of the major and escalating crises today. Impacts on biodiversity cascade to all natural ecosystems and the essential services they provide. “Amphibians are the most severely affected group of all vertebrates, with 40.7% of species facing an acute risk of extinction,†the authors state. With pesticide residues entering water bodies via various routes like spray drift, leaching, and run-off, these impacts on aquatic species need to be prioritized in risk assessments.
The current dependence on petrochemical pesticides and synthetic fertilizers subjects all humans and wildlife to chemicals that bring a myriad of health effects. There is a wide body of science linking pesticide exposure to asthma/respiratory effects, birth/fetal effects, brain and nervous system disorders, cancer, sexual and reproductive dysfunction, learning/developmental disorders, diabetes, immune system disorders, and endocrine disruption.
As the researchers state, “Herbicides, including glyphosate-based formulations, have been widely suggested to act as endocrine disruptors, which is especially critical given the key role of thyroid hormones during the amphibian metamorphosis.†(See additional studies here and here.) Take action to tell EPA that it must consider all data concerning endocrine disruption and must not register pesticides without sufficient data to demonstrate no unreasonable adverse endocrine risk.
National Forum
To learn more, plan to attend Beyond Pesticides’ 41st National Forum, Imperatives for a Sustainable Future! The second session, on Thursday, November 14, 2024, at 1 PM (EST), is with Tracey Woodruff, PhD, MPH, the director of the Program on Reproductive Health and the Environment at the University of California, San Francisco. Dr. Woodruff’s work focuses on uncovering and addressing environmental determinants of disease and health inequities, and she has written groundbreaking material on endocrine-disrupting chemicals. Dr. Woodruff is the author of “Health Effects of Fossil Fuel–Derived Endocrine Disruptors,†published earlier this year in The New England Journal of Medicine.
Roundtable Discussion
Dr. Woodruff’s talk will be followed by a roundtable with panelists, including a former senior scientist focusing on ecosystem effects, a breast cancer activist, and a farmworker advocate who will share their experience and insight into both the regulation of hazardous materials (including endocrine disrupting chemicals) and strategies for connecting science (and the power of those adversely affected) to decisions that eliminate hazards—recognizing disproportionate risk to people of color. Tapping the experiences of the panelists, this discussion brings together strategic thinking that supports efforts by individuals and organizations to transition away from petrochemicals from a range of perspectives and a broadening of coalition efforts. The panelists include: Les Touart, PhD, senior science and policy advisor, Beyond Pesticides—former senior EPA biologist and member of EPA’s Endocrine Disruptor Screening and Testing Advisory Committee; Janet Nudelman, director of program and policy, Breast Cancer Prevention Partners (BCPP); Mily Treviño-Sauceda, executive director and co-founder of Alianza Nacional de Campesinas, Inc., the first national grassroots farmworker women’s organization; and her colleague, Amy Tamayo, national policy and advocacy director, Alianza Nacional de Campesinas. Jay Feldman, executive director of Beyond Pesticides, will moderate.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source:
Flach, H. et al. (2024) Glyphosate formulations cause mortality and diverse sublethal defects during embryonic development of the amphibian Xenopus laevis, Chemosphere. Available at: https://www.sciencedirect.com/science/article/pii/S0045653524025244.
