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Assessment & Impacts » Health

Title: New evidence of dangers of Roundup weedkiller
Source: Third World Resurgence No. 176 Apr 2005
Publication date: April 01, 2005
Posting date: July 06, 2005

New evidence of dangers of Roundup weedkiller

New studies show that Roundup, one of the most common herbicides used worldwide for crops and backyard gardens, can have harmful health effects.
This has major consequences as the bulk of commercially planted GM crops are designed to tolerate Roundup with its active ingredient, glyphosate, and independent field data already shows a trend of increasing use of the herbicide.

Chee Yoke Heong

NEW studies from both sides of the Atlantic reveal that Roundup, the most widely used weedkiller in the world, can be harmful.

The stakes are high because more than 75% of genetically modified (GM) crops worldwide are engineered to tolerate glyphosate, with Monsanto's Roundup brand holding the biggest market share.

The use of Roundup has gone up especially in countries growing Roundup-tolerant GM crops engineered by Monsanto, who also produces the herbicide. It eliminates all other plants except the GM crops that are genetically engineered to be tolerant to it. Although the Roundup patent expired in September 2000, Monsanto is able to keep a captive and growing market for its weedkiller because the crops concerned are engineered to tolerate only Roundup.

Roundup with its active ingredient glyphosate has long been promoted as safe for humans and the environment while effective in killing weeds. It is a combination of glyphosate with other chemicals including a surfactant (detergent) polyethoxylated tallowamine that enhances the spreading of the spray droplets on the leaves of plants.

However, two recent studies show that Roundup, which is used by farmers and others including home gardeners, is not as safe as its promoters claim. This has major consequences as the bulk of commercially planted GM crops are designed to tolerate glyphosate (and especially Roundup), and independent field data already shows a trend of increasing use of the herbicide. This goes against industry claims that herbicide use will drop and that these plants will thus be more 'environment-friendly'. Now we find that there are serious health effects, too.

Roundup threatens human health

A group of scientists led by biochemist Professor Gilles-Eric Seralini from the University of Caen in France found that human placental cells are very sensitive to Roundup at concentrations lower than that in agricultural use. The findings were published in a US journal, Environmental Health Perspectives, in March.

According to French publication Le Monde, Seralini, as a member for years of the French Commission on Biomolecular Genetics (CBG), responsible for preparing the files for requests for field studies, then GMO (genetically modified organism) commercialisation, 'ceaselessly demands more intense studies on their eventual health impact'.

An epidemiological study in the Ontario farming populations showed that glyphosate exposure nearly doubled the risk of late spontaneous abortions, and Seralini and his research team decided to find out more about the effects of the herbicide on cells from the human placenta.

The French team used human placental cell lines, in which very weak doses of glyphosate showed toxic effects and, at still weaker concentrations, endocrinal disturbances.

The study thus showed that glyphosate is toxic to human placental cells, killing a large proportion of them after 18 hours of exposure at concentrations below that in agricultural use. This, they suggest, could explain the high levels of premature births and miscarriages observed among women farmers in the US using glyphosate.

They warn that since glyphosate is used worldwide, its residues may thus enter the food chain, and glyphosate is found as a contaminant in rivers. While Roundup and similar products were originally used against weeds, 'they have become a food product, since they are used on GMOs, which can absorb them without dying,' Seralini told Le Monde.

The scientists also compared the toxic effects of Roundup (the most common commercial formulation of glyphosate and chemical additives) and glyphosate (the active ingredient) by itself. They found that the toxic effect increases in the presence of Roundup 'adjuvants' or additives. These additives thus have a 'facilitating' role, with the result that Roundup is always more toxic than its active ingredient, glyphosate, at least by two-fold.

The toxic effect also increased with time, and was obtained with concentrations of Roundup 10 times lower than in agricultural use.

They concluded that the harmful effects of Roundup (the combination of chemicals) and not only glyphosate (the active ingredient) can be observed in mammals. Seralini is calling for extended animal studies.

Roundup 'lethal'

Another new study by scientists in the University of Pittsburgh, released in April, suggests that Roundup is also a danger to other life forms and non-target organisms.

Biologist Rick Relyea has found that Roundup is 'extremely lethal' to amphibians. In what is considered one of the most extensive studies on the effects of pesticides on non-target organisms in a natural setting, Relyea found that Roundup caused a 70% decline in amphibian biodiversity and an 86% decline in the total mass of tadpoles.

Leopard frog tadpoles and gray tree frog tadpoles were completely eliminated and wood frog tadpoles and toad tadpoles were nearly eliminated. One species of frog, spring peepers, was unaffected.

'The most shocking insight coming out of this was that Roundup, something designed to kill plants, was extremely lethal to amphibians,' Relyea, who conducted the research at the university's Pymatuning Laboratory of Ecology, said in a statement released by the University of Pittsburgh Medical Center. 'We added Roundup, and the next day we looked in the tanks and there were dead tadpoles all over the bottom.'

'We've repeated the experiment, so we're confident that this is, in fact, a repeatable result that we see,' said Relyea. 'It's fair to say that nobody would have guessed Roundup was going to be so lethal to amphibians.'

Relyea initially conducted the experiment to see whether Roundup would have an indirect effect on the frogs by killing their food source, the algae. However, he found that Roundup, although a herbicide, actually increased the amount of algae in the pond because it killed most of the frogs. 'It's like killing all the cows in a field and seeing that the field has more grass in it - not because you made the grass grow better, but because you killed everything that eats grass,' he said.

More warnings

In 2002 a scientific team led by Robert Belle had shown that Roundup acted on one of the key stages of cellular division, which can potentially lead to cancer in the long term.

Belle is from the National Center for Scientific Research (CNRS) biological station in Roscoff (Finistere, Brittany, France) and his team has been studying the impact of glyphosate formulations on sea-urchin cells for several years. They used a recognised model for the study of early stages of cancer genesis, which had earned Tim Hunt the 2001 Nobel Prize in medicine.

The team has recently demonstrated in Toxicological Science (December 2004) that a 'control point' for DNA damage was affected by Roundup, while glyphosate alone had no effect. 'We have shown that it's a definite risk factor, but we have not evaluated the number of cancers potentially induced, nor the time frame within which they would declare themselves,' Belle acknowledges.

There is, indeed, direct evidence that glyphosate inhibits an important process called 'RNA transcription' in animals, at a concentration well below the level that is recommended for commercial spray application. Transcription was inhibited and embryonic development delayed in sea urchins following exposure to low levels of the herbicide and/or the surfactant polyethoxylated tallowamine. This means that sprayers who inhale the chemical are exposed to health hazards.

There is also new research that shows that a brief exposure to commercial glyphosate caused liver damage in rats, as indicated by the leakage of intracellular liver enzymes. The research indicates that glyphosate and its surfactant in Roundup were also found to act in synergy to increase damage to the liver.

Three recent case-control studies suggested an association between glyphosate use and the risk of non-Hodgkin lymphoma; a prospective cohort study in the US states of Iowa and North Carolina that includes more than 54,315 private and commercial licensed pesticide applicators suggested a link between glyphosate use and multiple myeloma. Myeloma has been associated with agents that cause either DNA damage or immune suppression.

This accumulation of scientific studies requires more safety research to be done, and provides a strong case for governments to urgently review the use of Roundup and other forms of glyphosate. At the same time, GM crops that are herbicide-tolerant should not be allowed to be grown.


'Glyphosate Toxic & Roundup Worse', Institute for Science in Society Press Release, 7 March 2005.
'Roundup highly lethal to amphibians', University of Pittsburgh; Public release date: 1 April 2005
'Roundup Doesn't Poison Only Weeds' (translated from French), Herve Morin, Le Monde, 12 March 2005 (

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