A recent report from the U.S. Centers for Disease Control and Prevention found that more than 80 percent of urine samples from children and adults in the U.S. contained the herbicide glyphosate. A study from Florida Atlantic University and Nova Southeastern University goes a step further and is the first to link the use of the herbicide Roundup, a commonly used weed killer, to convulsions in animals.
Glyphosate, the herbicidal ingredient in Roundup, is the world’s most widely used herbicide by volume and per land area treated. Glyphosate-resistant crops account for nearly 80 percent of transgenic farmland, resulting in an estimated 6.1 billion pounds of glyphosate being sprayed around the world from 2005 to 2014. Roundup is used at both an industrial and consumer level, and its use is expected to increase significantly in the coming years. An important question, yet to be fully understood, is the potential impact of glyphosate on the nervous system.
“It is concerning how little we understand the impact of glyphosate on the nervous system,” said Akshay S. Naraine, MSc., project leader and a Ph.D. student at FAU and the International Max Planck Research School for Synapses and Circuits. “There is mounting evidence of just how common glyphosate exposure is, so hopefully this work encourages other researchers to expand on these findings and establish where our concerns should be.”
Results, published in scientific reports, showed that glyphosate and Roundup increased the attack-like behavior of soil-dwelling roundworms and provides significant evidence that glyphosate targets GABA-A receptors. These communication points are essential for locomotion and are heavily involved in regulating sleep and mood in humans. What really sets this study apart is that it was done at significantly fewer levels than recommended by the EPA and the levels used in previous studies.
“The concentration listed for best results on the Roundup Super Concentrate label is 0.98 percent glyphosate, which is about 5 tablespoons of Roundup in 1 gallon of water,” Naraine said. “A key finding from our study reveals that only 0.002 percent glyphosate, a difference of about 300 times less herbicide than the lowest recommended concentration for consumer use, had worrisome effects on the nervous system.”
Using C. elegans, a soil-dwelling roundworm, researchers first tested glyphosate alone and then tested both the US and UK formulations of Roundup from two different time periods – before and after the UK’s 2016 ban on polyethoxylated tallowamines (POEAs). ). These conditions were selected to determine the effects specific to the active ingredient glyphosate, Roundup formulations in general, the POEA surfactants or a combination of these.
The study found that the active ingredient glyphosate exacerbated seizures in C. elegans and suggests that the GABA-A receptor is a neurological target for the physiological changes observed. The data also indicate that there is an important distinction between glyphosate and Roundup exposure, with Roundup exposure increasing the percentage of C. elegans that did not recover from attack activity. The non-recovery phenotype and prolonged convulsions in C. elegans from this study helped establish a foundation for understanding nuanced physiological effects of herbicides occurring at concentrations exponentially below neurotoxic levels.
“Given how widespread the use of these products is, we need to learn as much as we can about the potential negative effects that may exist,” said Ken Dawson-Scully, Ph.D., chief of the lab, professor, senior vice president, and associate provost, Department of Research and Economic Development, Nova Southeastern University. “There have been studies in the past showing the potential dangers, and our study takes it one step further with some pretty dramatic results.”
The findings also raise concerns about the impact of herbicide use on soil organisms such as C. elegans.
“These roundworms undergo convulsions under thermal stress, and our data strongly imply that exposure to glyphosate and Roundup exacerbates the convulsive effects. This could be vital as we experience the effects of climate change,” Naraine said.
This study provides evidence to further explore how chronic exposure and accumulation may lead to neurodegenerative diseases such as Parkinson’s disease. Importantly, there is also a sub-neurodegenerative threshold that can dramatically affect neurotransmission dysregulation.
“As of now, there is no information on how exposure to glyphosate and Roundup could affect people diagnosed with epilepsy or other seizure disorders,” Dawson-Scully said. “Our study indicates that there is significant disruption in locomotion and should lead to further studies in vertebrates.”
Co-authors of the study are Venkatesh Shanbhag, Ph.D., chief chemist and professor of chemistry, Halmos College of Arts and Sciences, NSU; Rebecca Aker who was a master’s student at FAU while contributing to this research; and Isis Sweeney, Meghan Kalvey, and Alexis Surtel, undergraduate students who contributed to the FAU.
Roundup exposure prolongs epileptic behavior in roundworms
The Impact of Roundup and Glyphosate on GABA to Provoke Prolonged Proconvulsive Behavior in 12 Caenorhabditis elegans, Scientific Reports (2022). DOI: 10.1038/s41598-022-17537-w
Provided by Florida Atlantic University
Quote: Study First to Link Weed Killer Roundup to Animal Convulsions (2022, Aug. 23) retrieved Aug. 23, 2022 from https://phys.org/news/2022-08-link-weed-killer-roundup-convulsions.html
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