Roundup Weedkiller Linked to Convulsions in Animals

A person in protective workwear sprays herbicide in a field
A person in protective workwear sprays herbicide in a field. Adriana Duduleanu / EyeEm / Getty Images
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Recently, the U.S. Centers for Disease Control and Prevention released a report that found more than three quarters of urine samples tested from adults and children in the U.S. contained glyphosate, the herbicide used in Roundup weedkiller, a press release from Florida Atlantic University (FAU) said. A new FAU and Nova Southeastern University study has gone further and found a link between the weedkiller and convulsions in animals.

Glyphosate is the most frequently used weed killing chemical by volume and area of land treated in the world, and nearly 80 percent of land cultivated for genetically modified (GM) crops contain crops that are resistant to glyphosate. More than 13 billion pounds of glyphosate were applied to crops globally from 2005 to 2014.

The use of Roundup weedkiller commercially and by individual consumers is predicted to go up considerably in the future, but the possible range of effects of the chemical on the nervous system is not entirely known.

“It is concerning how little we understand the impact of glyphosate on the nervous system,” said Akshay Naraine, a Ph.D. candidate at FAU and the International Max Planck Research School for Synapses and Circuits, who was the lead author of the study, as reported by The Hill. “More evidence is mounting for how prevalent exposure to glyphosate is, so this work hopefully pushes other researchers to expand on these findings and solidify where our concerns should be.”

The results of the study, “Roundup and glyphosate’s impact on GABA to elicit extended proconvulsant behavior in Caenorhabditis elegans,” were published in the journal Scientific Reports.

The researchers found an increase in seizure-like behavior in the soil-dwelling roundworms C. elegans due to the glyphosate found in Roundup, the press release said. The findings provided compelling evidence that GABA-A receptors — transmission points necessary for movement — are targeted by glyphosate.

What makes the study unique is that it used dramatically lower amounts of glyphosate than were used in former studies and lower levels than are suggested by the U.S. Environmental Protection Agency (EPA).

“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 in the press release. “A significant finding from our study reveals that just 0.002 percent glyphosate, a difference of about 300 times less herbicide than the lowest concentration recommended for consumer use, had concerning effects on the nervous system.”

Initially, the research team conducted tests on C. elegans using glyphosate by itself, then with the UK and U.S. formulas of Roundup from two separate time frames. The first was before the UK banned polyethoxylated tallowamine (POEAs) in 2016, and the second was after the ban.

The scientists set up these parameters in order to find out which of the results were caused by the POEAs, glyphosate, Roundup, or any mixture of the three.

The team found that convulsions in C. elegans were made worse by glyphosate, which points to the physiological effects being caused by the chemical targeting the GABA-A receptor.

The results also suggest that more C. elegans didn’t recover from convulsions following exposure to Roundup.

The study’s findings have provided a basis for understanding the subtleties of the effects of weedkillers at far lower levels than have been historically considered toxic to the nervous system.

“What truly sets this research apart is that it was done at significantly less levels than recommended by the EPA and those used in past studies,” the researchers said, as The Independent reported.

Dr. Ken Dawson-Scully of the Division of Research and Economic Development at Nova Southeastern University said that, because the weedkillers are so commonly used, their possible adverse effects must be explored as much as possible.

“There have been studies done in the past that showed the potential dangers, and our study takes that one step further with some pretty dramatic results,” Dawson-Scully said in the press release.

The results of the study have brought up concern regarding the possible effects of herbicides on C. elegans and other soil-dwelling creatures.

“These roundworms undergo convulsions under thermal stress, and our data strongly implicates glyphosate and Roundup® exposure in exacerbating convulsive effects. This could prove vital as we experience the effects of climate change,” Naraine said in the press release.

The findings of the study can serve as a building block for the exploration of the ways in which chronic exposure to these chemicals could result in neurodegenerative diseases like Parkinson’s. The study also demonstrates that neurotransmitter regulation could be disrupted at levels below those that result in neurodegeneration.

“As of now, there is no information for how exposure to glyphosate and Roundup® may affect humans diagnosed with epilepsy or other seizure disorders,” Dawson-Scully said in the press release. “Our study indicates that there is significant disruption in locomotion and should prompt further vertebrate studies.”

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