RoundUp: World’s most popular weed-killer linked to convulsions in animals for first time

Scientists say it is ‘concerning how little we understand’ about impact of glyphosate on nervous system

Harry Cockburn
Environment Correspondent
Tuesday 23 August 2022 15:30 BST
An estimated 6.1 billion kilos of glyphosate were sprayed across the world from 2005 to 2014
An estimated 6.1 billion kilos of glyphosate were sprayed across the world from 2005 to 2014 (Getty)

The world’s most widely used weed-killer has been linked to convulsions in animals for the first time, according to startling new research by US academics.

Industrial quantities of glyphosate – the herbicide used in RoundUp weedkiller – are sprayed across agricultural land and used in gardens around the world, with a recent report warning that more than 80 per cent of urine samples from people in the US now contained glyphosate due to its pervasiveness in the food chain.

With genetically modified glyphosate-resistant crops (originally engineered by RoundUp’s parent company Monsanto) now accounting for over 80 per cent of all US crops, and being grown commercially around the world, use of glyphosates is projected to rise dramatically.

However, the research now raises serious questions about 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 Naraine, project lead and a PhD student at Florida Atlantic University and the International Max Planck Research School for Synapses and Circuits.

“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 research team found that glyphosate and RoundUp "increased seizure-like behaviour" in soil-dwelling roundworms.

Their investigation "provides significant evidence" that glyphosate targets some core functions of the central nervous system, most notably the GABA-A receptors in nerve cells.

The team said the GABA-A receptors "are essential for locomotion and are heavily involved in regulating sleep and mood in humans".

"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.

“The concentration listed for best results on the RoundUp Super Concentrate label is 0.98 per cent glyphosate, which is about 5 tablespoons of RoundUp in 1 gallon of water,” said Mr Naraine.

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

Using the soil-dwelling roundworm C. elegans, the research team first tested glyphosate alone and then both the US and UK formulations of RoundUp.

They also tested the UK product from two distinct time periods – before and after the 2016 ban on polyethoxylated tallowamine (POEAs). These additional chemicals are made from animal fats and are designed to deliver the poisonous glyphosates deeper into plant tissues.

The various products and tests enabled the team to pinpoint which effects are specific to the active ingredient glyphosate, RoundUp formulations in general, the POEAs, or any combination of these.

The team found that the active ingredient glyphosate exacerbated convulsions in the worms.

However, the data also indicated that there is an important distinction between exposure to glyphosate and RoundUp, with RoundUp exposure increasing the percentage of worms which ultimately died following the seizures caused by the chemicals.

The deaths and prolonged convulsions observed in the worms "have helped to set a foundation for understanding nuanced physiological effects of herbicide that occur at concentrations exponentially below neurotoxic levels", the researchers said.

“Given how widespread the use of these products is, we must learn as much as we can about the potential negative impacts that may exist,” said Dr Ken Dawson-Scully from Nova Southeastern University.

“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.”

With the growing appreciation of the essential role worms play in maintaining fertile soils, the team said their findings "generate concern over how herbicide use might affect soil-dwelling organisms".

They also suggested impacts from herbicides like RoundUp could further imperil worms already struggling due to other agricultural pressures and the worsening climate crisis.

“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,” said Mr Naraine.

Furthermore, the team warned that human exposure to these products remains under-investigated.

They said the research "provides evidence to further investigate how chronic exposure and accumulation may lead to neurodegenerative diseases such as Parkinson’s disease".

“As of now, there is no information for how exposure to glyphosate and RoundUp may affect humans diagnosed with epilepsy or other seizure disorders,” said Dr Dawson-Scully.

“Our study indicates that there is significant disruption in locomotion and should prompt further vertebrate studies.”

A spokesperson for Beyer, the owner of the Roundup brand, told The Independent: “It is important to note that this research was conducted with worms. Research with worms does not meet the scientific standards necessary to predict effects on humans or other mammals for the purposes of a pesticide safety assessment.

“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. 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.”

The research is published in the journal Scientific Reports.

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