Thursday, December 1, 2022 | Back issues
Courthouse News Service Courthouse News Service

Popular weed killer linked to animal convulsions

Researchers applied 300 times less Roundup than the amount recommended on the bottle label.

(CN) — Researcher Akshay Naraine of Florida Atlantic University acknowledges we know little of the effects weed killers have on our nervous systems. But he has discovered one thing: a link between the active ingredient in Roundup and convulsions in soil-dwelling roundworms.

Published in Scientific Reports, Naraine's study focused on Roundup’s active ingredient glyphosate and explored its effects on animal and human nervous systems. Concerned about the lack of data, Naraine tested the effects based on a colleague’s lab technique.

“Electroshock convulsion analysis in soil-dwelling roundworms was a technique developed in Dr. Ken Dawson-Scully’s lab, and while the majority of the work focused on screening novel antiepileptic drug candidates, I wanted to flip the script and test an environmental chemical,” Naraine said in an email. “There was little evidence that glyphosate affected convulsive behavior prior to our study, so the project started in an exploratory manner to determine if the lab’s assay could detect changes brought on by pesticides.”

The study shows glyphosate and Roundup increased seizure-like behavior in the soil-dwelling roundworm species C. elegans. Specifically, glyphosate targets GABA-A receptors, chemical connection points in the roundworm's nervous system.

“In these roundworms, GABA-A receptors are essential for movement and blocking them impairs movement,” Naraine said in the email. “But in the human brain, blocking GABA-A receptors can affect sleep and contribute to depression and anxiety disorders.”

Before testing on the roundworms began, the researched worried when they found that the concentration was at “significantly less levels” than recommended by the U.S. Environmental Protection Agency.

“The concentration listed for best results on the Roundup Super Concentrate label is 0.98% glyphosate, which is about 5 tablespoons of Roundup® in 1 gallon of water,” Naraine said in a statement accompanying the study. “A significant finding from our study reveals that just 0.002% glyphosate, a difference of about 300 times less herbicide than the lowest concentration recommended for consumer use, had concerning effects on the nervous system.”

Per the study, researchers first tested glyphosate on a single soil-dwelling roundworm. Then, they tested the U.S. and United Kingdom versions of Roundup from before and after the U.K.’s 2016 ban on polyethoxylated tallowamine (POEAs). Not an easy task considering the secrecy of the Roundup adjuvant composition.

“The adjuvant is the trade secret mix of other chemicals meant to enhance glyphosate’s weed-killer effects, and since it is a trade secret, the chemical contents are not publicly disclosed,” Naraine wrote.

Naraine and the team found glyphosate exacerbated convulsions in the roundworms, a species already vulnerable to convulsions due to thermal stress. This suggests the GABA-A receptor was a neurological target for the observed physiological changes.

“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.

The researchers say their findings provide further evidence that chronic exposure to glyphosate and weed killers may lead to neurodegenerative diseases such as Parkinson’s disease.

“A 2012 study from King College in Tennessee showed that high amounts of glyphosate degraded dopamine neurons in soil-dwelling roundworms, but more research needs to be done to clarify what chronic exposure effects may result in,” wrote Naraine, adding the roundworms' reactions to the short period of exposure was concerning. “It is truly unique to uncover that glyphosate and Roundup can lead to such significant changes in movement at levels over 300-fold lower than those recommended on the back of the bottle of Roundup.”

In an emailed statement, Roundup manufacturer Bayer noted the study involved worms, not mammals, and the results should not be used to project Roundup's effects on mammals.

"Safety scientists at regulatory agencies around the world have reviewed glyphosate and the other ingredients in glyphosate-based herbicides and specifically considered whether they can harm the nervous system based on data from high-dose studies in mammals, not worms," the company said in a statement. "Scientists that have reviewed all of the available data have concluded that neither glyphosate nor the other ingredients in glyphosate-based herbicides will harm the nervous system at doses much greater than what any human would be exposed to."

As it stands, the study says more than 13 billion pounds of glyphosate was sprayed worldwide from 2005 to 2014, and its use is projected to dramatically increase in the future.

Read the Top 8

Sign up for the Top 8, a roundup of the day's top stories delivered directly to your inbox Monday through Friday.

Loading
Loading...