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Human skin forms a barrier to glyphosate, but there are many other ways in which people are exposed to it. Anyone near or down-wind of a crop being sprayed, or anyone using spraying equipment will inhale glyphosate. Anyone handling the equipment subsequently or touching sprayed areas can, inadvertently, transfer the weed-killer to their mouth. Anyone eating food from a crop treated with glyphosate pre-harvest, or a GM crop able to accumulate the herbicide, will have oral and digestive system exposure to the weed-killer (and food trapped between teeth could provide glyphosate exposure there for a considerable time).
Glyphosate has been a popular chemical because its safety-profile is much better than other herbicides. It's highly water-soluble and so can be washed out of the environment and the body. Since it acts on weeds by interfering with a vital protein-generating enzyme entirely specific to plants, there's been no concern about its safety for animals.
However, the story of glyphosate isn't quite as simple as that.
To exert its herbicidal effects, glyphosate has to be inside the plant cell. This means penetrating the plants' waxy outer protective layer and the fat-rich cell membrane. Water-soluble glyphosate isn't good at either.
Overcoming this problem involves mixing the herbicide with other chemicals which breach the living layers glyphosate has to get through. Glyphosate plus various other chemicals is sold under the brand-name, 'Roundup'. Such 'other chemicals' are largely 'confidential business information', so the science about them is patchy. The main ingredient of older Roundup formulations is known, but the make up of newer, super-fast acting and more lethal concoctions is kept under wraps. The safety concern here is that the action of Roundup with all its various secret chemicals is not plant specific.
Add to this that when glyphosate is shipped efficiently into any living cell, it will cause health problems: the herbicide molecule is able to bind the trace ions needed for many vital enzymes involved in the life-processes.
There's an increasing body of evidence showing that Roundup is harmful to animal cells, and that Roundup is invariably more toxic than glyphosate alone.
A recent paper (Koller et al.) noted studies which indicate that epithelial cells are especially susceptible to the damaging properties of glyphosate and Roundup. Epithelial tissues form a protective layer covering organs and other structures in the body. The mouth and respiratory tract are lined with epithelial cells.
When a team of Austrian scientists asked the question, 'what effects do glyphosate and Roundup have on the cells lining the mouth?', they come up with some very unpleasant results.
Roundup induced clear, dose-dependent, damage to the cell, including disruption of outer membranes and the mitochondria (membranous structures inside all cells which produce their energy), gross DNA and nuclear changes (the nucleus is also membrane-bound), and cell death. Glyphosate on its own was less potent, but was found to cause measurable cell-membrane damage, cell nuclear disruption and cell death.
The observed effects of glyphosate and Roundup were on human cells, known to be exposed to the chemicals. Damage was evident after a very short time and at very low concentrations. The indications are that glyphosate and Roundup can predispose us to cancer and to respiratory and digestive tract disease. There's no reason to assume that chronic exposure to trace levels in our food would be innocuous.
The Institute of Science in Society concluded that the Austrian evidence “adds yet more weight to an outright ban of (glyphosate)”. Hear, hear.
For more information, check out Ban Glyphosate Herbicides Now at the Institute of Science in Society, and follow the links to other Institute of Science in Society articles on glyphosate.
- Koller V. J., et al., 2012, Cytotoxic and DNA-damaging properties of glyphosate and Roundup in human-derived buccal epithelial cells, Archives of Toxicology, 14.02.12
- Glyphosate Toxic to Mouth Cells & Damages DNA, Roundup Much Worse, Institute of Science in Society Report 28.03.12