Safe as salt? Not Roundup

April 2011

There's no such thing as a poison that's 'safe as salt' Roundup is no exception.

Here are some of the claims made by Monsanto...

“Roundup is tough on plants, but no more toxic to people and animals than table salt” (Monsanto Europe, December 1995)

“... Roundup, a herbicide widely known for its very favourable environmental profile.” (Monsanto website, November 1996)

“Applying Rounup over soyabeans doesn't raise herbicide residues above existing residue standards” (Monsanto Europe, December 1995)

“ * Roundup has been used commercially for more than 20 years ... in more than 100 countries.
* Glyphosate is rapidly broken down in soil by naturally occurring soil microorganism
* Roundup is effective ... eliminating the need for additional herbicides in Roundup Ready soyabeans” (Monsanto Europe, undated but pre-1997)

This seems very reassuring. It tells us that Roundup herbicide has been around for years all over the world, long before the GM crops designed to be sprayed with it came on the scene. It's safe to eat, environmentally friendly, naturally disappears to negligible levels, and saves any need for additional weed-killers.

Comforting. But is it true?

The final claim has been the first one to unravel.

Between 1994 (pre-GM) and 2005 (nine years post-GM), US government data reveal a 15-fold increase in the use of glyphosate; the following year, glyphosate use jumped a further substantial 28%.

This has been due to a number of Roundup-related changes in farming practice:
  • Whereas before the introduction of Roundup Ready (RR) crops, Roundup was used as a one-off burndown to clear fields of weeds before any crop seedlings emerged (or they would have been killed by the herbicide), now the food crops themselves can be sprayed liberally and repeatedly with the weed-killer.
  • Plants actively absorb Roundup and some Roundup Ready plants have been found to take in 15% more than their conventional counterparts. This means a lot of the Roundup applied to a GM field disappears into the crop plants without ever reaching the weeds it's supposed to be killing.
  • Four out of every five GM crops are already Roundup Ready varieties, and Monsanto is incorporating the RR trait into nearly every GM seed it sells.
  • No-till farming, which uses Roundup instead of a plough, has become more widely practiced
  • The rotation of RR soya with RR maize, each with its own doses of Roundup has become increasingly common.

The result has been, as predicted right from the start of RR crops, the emergence of some very problematic Roundup-resistant weeds, and a spiraling cycle of increased spraying using more Roundup plus some very less ‘friendly’ weed-killers.

Monsanto's promised elimination of the “need for additional herbicides” was short-lived.

The Company's assertion that 'Glyphosate is rapidly broken down in soil' also needs qualification.

If glyphosate is actually in the soil, and if the soil conditions are conducive, and if the right micro-organisms are there, glyphosate can be degraded in a few days.

However, most of the 'disappearance' of glyphosate from the soil is due to dissipation rather than degradation. Glyphosate readily washes away in soil water, and tends to attach itself to minerals such as soil particles, or magnesium or calcium in solution. Under the wrong soil conditions, microbial breakdown of glyphosate can take several weeks, and the total clearance of the herbicide from soil can take several months.

Monsanto's natural rapid breakdown of glyphosate by soil micro-organisms isn't untrue, it's just a very small part of the bigger picture.

The successful history of widespread use of Roundup is true. However, again it needs qualification.

Look at the US government figures for increased use of Roundup quoted above, and the changes in agricultural practice which have led to them.

The suggested long history applies to the use of the weed-killer on weeds, not on the crops you eat. Part of that 15-fold increase is now going into the plants which produce your food.

But, you may well ask, if Roundup is safe as salt and generally dissipates quickly from the environment, does it really matter if there's a bit more of it around and some of that bit is in our food?

Monsanto's claim that Roundup is 'no more toxic ... than table salt' is supported by a report on the safety of glyphosate prepared jointly by the UN Environment Programme, International Labour Organisation and the World Health Organisation in 1994. This summarised the data available at the time. It noted low toxicity in a wide range of animal species, and few effects in most tests except at very high dosages of the herbicide.

There are, however, a few alarm bells in this report. For example:
  • Inhibitory effects on soil fungi and nitrogen-fixing bacteria (both vital for soil health) were noted.

The resulting deleterious effects of glyphosate on nitrogen-fixation in RR soya roots have since been confirmed. This is a cause for concern for agriculture in the long-term because “even a small reduction in nitrogen fixation potential may have long-term effects on sustainable soil nitrogen pools, considering the widespread adoption of the (glyphosate resistant) soyabean system” (Zablotowicz and Reddy, 2004) 
  • Measurements of daily human intake of glyphosate from food and drinking water were unavailable, and data from monitoring programmes on glyphsate levels in the environment were very scarce. Animal studies suggest a third of glyphosate consumed is absorbed into the body, from which it is cleared unchanged after a few days.

In the field, glyphosate is taken into the leaves of the plants from where it is actively moved to different parts of the shoot and root where it accumulates unchanged.

The overall impression from all the above descriptions of the fate of the herbicide in the soil, in water, in animals, and in plants, is that glyphosate hangs around in the system: it isn't metabolised in plants or animal (including food-animals), once consumed it isn't processed by the digestive or immune systems, so the only way to get rid of it is by slowly flushing it out. Glyphosate has a habit of attaching itself to things in the soil which have parallels in the living system. What mischief might it get up to inside you during the days before it is cleared? And of course, if you're eating traces of glyphosate at every meal, it suggests there would be small amounts perpetually flowing through your body.

This hanging around in the environment and inside us raises a safety question, especially if no one knows exactly how much we're consuming.

A reviewer of data on glyphosate residue levels in 2005 commented “surprisingly little has been published on herbicide residues in (glyphosate resistant crop) foods ...”. He noted a single published study which reported, as Monsanto assured us, that glyphosate residues are “within established tolerance levels” in harvested seeds. Beyond this, it seems all we have to rely on are the herbicide residue data presented for regulatory approval as supplied by Monsanto. Tolerance levels are of course set at many times below measured concentrations toxic to animals. But, see below.
  • The safety of glyphosate's major degradation product, AMPA (aminomethylphosphonic acid) is barely mentioned. Soil levels of AMPA could reach levels of 25% of the applied dose and were found in fish up to three months after exposure.

The single published study on herbicide residues inexplicably found greater amounts of AMPA than glyphosate in the seeds despite the science which has shown that plants are unable to degrade the herbicide. This begs the question, are the glyphosate levels in food being kept below tolerance standards because the herbicide is being replaced by something else no one's testing for? Which brings us to a more obviously serious alarm bell. 
  • Most experiments seem to have been carried out using chemical glyphosate. There is a single mention of a study indicating that, in the case of aquatic invertebrates, Roundup has a higher toxicity than glyphosate “mainly due to the presence of surfactants.”
This is a bit of an understatement of the situation because 'Roundup' is marketed in several formulations containing anything from 7 to 45 percent glyphosate and a varying cocktail of secret chemicals (such as surfactants) all designed to get glyphosate into the plant and to kill it more effectively. Newer Roundup formulations also have additional more toxic herbicides added in.

Another piece of this jigsaw was added when Italian researchers noted that cellular toxic responses in laboratory animals fed Roundup Ready soya were very similar to those caused by glyphosate. While some animal feeding studies have identified adverse effects from RR-spiked chow, others have not, but none of these studies measured the levels of glyphosate or Roundup in the feed used.

Four pivotal scientific papers looking at physiological effects of Roundup in animal cells have given real cause to question the safety of the formulations. Two found modifications in the membranes of mitochondria (these are vital cellular bodies which generate the energy to power all cell functions) after treatment with Roundup suggestive of a decline in mitochondrial activity. One found other signs of decreased activity, for example, in the cell nucleus. The third study found Roundup interferes with the pathway for endocrine hormone synthesis. The fourth found Roundup induced cell death. There was clear evidence that the problems were attributable to Roundup, and not to glyphosate.

Ominously, similar harmful effects were observed with one of the few known adjuvants in Roundup, and with AMPA, glyphosate's breakdown product which is inexplicably turning up in harvested seed. The authors noted “surprisingly (or, perhaps, politely speaking) Roundup is always more toxic than its active ingredient, glyphosate” (Benachaur and Seffralini, 2005)


There are far too many serious safety questions here about the cocktail, and possibly cumulative, effects of the various Roundup formulations: what might all these secret unknowns and their secret derivatives and their secret interactions do to animal, environmental and human health?

Since GM animal feed is our main source of dietary Roundup, what quantity of these secret unknowns and their derivatives is being passed on to us in meat, milk and eggs?

Glyphosate may indeed be no more toxic than table salt, but that's a claim which doesn't extend to the actual mixture of chemicals being sprayed on our crops.

(This article is adapted from an article which appeared on GM-free Scotland in February 2009. The original article is archived here.)

  • Monsanto quotes from Monsanto Information Pack, January 1997
  • Pat Thomas, Behind the label: Roundup Weedkiller, The Ecologist, April 2008
  • Euroabio admits increased chemical to fight superweed, Thin Ice 10, March 2008
  • Hetherington et al., The absorption, translocation and distribution of the herbicide glyphosate in maize expressing the CP-4 transgene, Journal of Experimental Botany, 50:339, October 1999
  • International Programme on Chemical Safety, Environmental Health Criteria 159, GLYPHOSATE, jointly sponsored by UN Environment Programme, International Labour Organization, World Health Organization, Geneva 1994
  • Zablotowicz and Reddy, Impact of Glyphosate on the Bradyrhizobium japonicaum Symbiosis with Glyphosate-Resistant Transgenic Soybean, Journal of Environmental Quality, 33, 2004
  • Cerdeira and Duke, The Current Status and Environmental Impacts of Glyphosate-Resistant Crops, Journal of Environmental Quality, 35, 2006
  • Benachour and Seffralini, Glyphosate Formulations Induce Apoptosis and Necrosis in Human Umbilical, Embryonic, and Placental Cells, Chemical research in Toxicology, 22:1 2009
  • Richard et al., Differential effects of Glyphsate and Roundup on Human Placental cells and Aromatase, Environmental Health Pe5spectives, 113:6, June 2005
  • Peixoto, Comparative effects of Roundup and glyphosate on mitochondrial oxidative phosphorylation, Chemosphere, 61:8, December 2005
  • Malatesta et al., Hepatoma tissue culture (HTC) cells as a model for investigating the effects of low concentrations of herbicide on cell structure and function, Toxicology in Vitro, 18, September 2008
  • Who Benefits from GM Crops? Friends of the Earth Europe, February 2009

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