Safety regulation of 'Roundup' herbicide is based solely on its active, weed-killing, ingredient, 'glyphosate'*. Roundup formulations have a variety of added substances needed for glyphosate to be effective, but these are considered inert, and thus irrelevant, to safety.
*Note. Most GM crops are 'Roundup Ready', having been genetically transformed to tolerate glyphosate and accumulate it.
The result has been that glyphosate, and by implication Roundup, has a reputation for being the safest herbicide on the market. Indeed, acute exposure to pure chemical glyphosate has to be at a very high dosage before it becomes toxic, and this is true for both plants and animals.
However, sceptical scientists are questioning the validity of current 'safety' tests based on glyphosate alone. Their problem is that glyphosate is always used in a formula combined with adjuvants because otherwise it doesn't penetrate the cells and doesn't kill the weed.
Roundup is, of course, designed to kill plant cells. But what does it do to animal cells?
The scope of the question was spelled out by a French team of scientists in a paper published in 2010. There's a wide range of Roundups on the market. These have hugely varying concentrations of glyphosate. In France, for example, Roundup formulations are readily available with herbicide levels of anything from 7.2 to 450 grams/litre (a more than 60-fold difference). The adjuvants vary with Roundup type, and are a trade secret chosen from a long list of chemicals. This means when you test Roundup, you don't actually know what you're testing.
For scientists, if Roundup is toxic, the first organ to be affected is likely to be the liver, our main organ for detoxification of environmental pollutants. They can't experiment on people, but they have a number of liver cell cultures which have been well established as models for testing liver function.
When cultured cells were exposed to four different brand-name Roundups compared to chemical glyphosate, the formulae were all much more toxic than the herbicidal ingredient alone. Significant increases were found in cell mortality, and there was a disruption of the cells' detoxification mechanisms.
The Roundups' toxic effects weren't related to their glyphosate content. They were, however, time-dependent.
Liver cell DNA fragmentation caused by the same four Roundup formulations at very low doses have been reported. The amount of DNA damage was, in this case, glyphosate-dependent.
Another study looked at chemical glyphosate's effect on the same type of liver cells plus another classic model human cell line. This found a clear disruption to the generation of an important protective antioxidant in the cells.
The uncomfortable picture emerging here is a potential for Roundup to cause liver disease and to disrupt the liver's ability to deal with environmental toxins, while its glyphosate content disrupts the liver DNA and prevents the liver cells from protecting themselves against the harmful metabolic intermediates which arise during the detoxification process.
It's particularly worrying that, while there's ample evidence that glyphosate from Roundup is universally permeating through our bodies, no one really knows what we're being exposed to, nor how toxic that unknown is.
In the fields, where spraying with Roundup year-on-year is generating Roundup-resistant weeds, the levels of glyphosate are increasing and the adjuvants, whatever they are, are getting more aggressive to plants. How aggressive they may be to animals is another unknown.
Because Roundup's toxic effects accumulate with exposure time, there could be a much greater health risk from our current chronic low-dose levels than that evidenced by current safety tests.
With all manner of Roundups entering our food chain in GM staple crops and in drinking water, there's quite enough science here to justify a demand for each and every Roundup formulation to be withdrawn from the market and retested for safety on its own merits.
- Malin Hultberg, 2006, Cysteine turnover in human cell lines is influenced by glyphosate, Environmental Toxicology and Pharmacology 24
- Céline Gasnier, et al., 2010, Dig1 protects against cell death provoked by glyphosate-based herbicides in human liver cell lines, Journal of Occupational Medicine and Toxicology 5:29
- Céline Gasnier, et al., 2009, Glyphosate-based herbicides are toxic and endocrine disruptors in human cell lines, Toxicology 26