|Pesticide spraying. CC photo by Global Water Partnership on Flickr|
There could be as many as five million agricultural workers in the developing world who suffer an episode of pesticide poisoning each year. Some of these are accidental and some are, sadly, due to attempted suicide. In these latter cases, death is strongly associated with high blood glyphosate levels. Glyphosate is, of course, the active ingredient of Roundup herbicide used on, and accumulated by, GM 'Roundup Ready' crops.
Roundup intoxication commonly leads to heart malfunction. Anecdotal evidence from hunters describe rabbits dying suddenly after crossing a Roundup-sprayed field, and pet owners have described dogs dying of seizures after exposure to Roundup-sprayed lawns.
Despite these, Roundup's benign image remains intact . But the evidence that the herbicide is far from physiologically inert is mounting.
The latest published Roundup toxicity study sought to explain the link between the herbicide and cardiac function problems.
A French team, led by Steve Gress, investigated what happened when strips of rat and rabbit heart, stimulated to contract by electrical impulses, were exposed to Roundup or its active ingredient, glyphosate. The herbicide used was 'Roundup Ultra' which is freely available in France and which has 36% glyphosate plus 16% of an undeclared adjuvant added to increase the effectiveness of the glyphosate.
What they found was that glyphosate on its own had no effect. Roundup, however, progressively and irreversibly impaired the contractile function of the heart tissue. Further investigations of the mechanism of Roundup damage suggested that the vital flow and exchange of metal ions (sodium, calcium and potassium) in the heart cells was being blocked.
The picture suggested by these findings is that the adjuvants added to Roundup to breach plant protective structures so that the glyphosate can penetrate into the plant cells and kill them, are also able to compromise the integrity of animal cell membranes. Glyphosate, which is inert if kept outside the cell, is thus brought into contact with the cells' metal ions which it binds and immobilises. Roundup's active ingredient may not kill the heart cells, but it could be destroying their function and kill the animal.
The concentrations of Roundup and glyphosate used in this experiment modelled those found in the blood passing through the heart of a suicide or accidental poisoning victim, and was much higher than levels used in routine agriculture. Much of the world's population now seems to be drip-fed Roundup and glyphosate in their food, water and environment , but surely the odd dysfunctional heart cell resulting from chronic low-level exposure won't kill anyone.
Or will it?
Bear in mind that:
- Exposure to Roundup and glyphosate starts in the womb and continues throughout life 
- Our exposure to Roundup is steadily rising due to increasing commercialisation of Roundup Ready food and feed crops, due to increased spraying of such GM crops in response to emerging Roundup-resistant weeds, and due to regulators who have no qualms about setting a maximum residue level (MRL) to suit farmers' desire to spray rather than to safeguard consumers.
- The damaging effect of Roundup on heart cells found in Gress's experiment was irreversible, and therefore cumulative over time.
No one's going to keel over from heart-failure after eating a few lentils dried down with Roundup, but a lifetime of Roundup gnawing away at your heart cells could be a part of the oddly parallel increase in heart disease and Roundup application now showing up in America .
We urgently need in-depth scientific testing of the effects of chronic exposure to Roundup on all organ systems, and clinical trails. Keep asking for it.
 GLYPHOSATE: SAFE AS SALT? - GMFS (Archive), February 2009
 A WORLD AWASH WITH GLYPHOSATE - April 2014
 GM PESTICIDES INSIDE YOU - April 2011
 HOW MUCH DISEASE IS ROUNDUP CAUSING? - December 2014
- Steeve Gress, et al., 2014, Cardiotoxic electrophysiological Effects of the Herbicide Roundup in Rat and Rabbit Ventricular Myocardium In Vitro, Cardiovascular Toxicology 2.12.14
- Rosemary Mason, How Roundup Poisoned my Nature Reserve, Science in Society 64, Winter 2014