August 29, 2016
Glyphosate — the active ingredient of Monsanto’s blockbuster herbicide Roundup — may disrupt development of the uterus, leading to fertility problems and cancer, according to a study conducted by researchers from Argentina and published in the journal Toxicology.
Roundup is one of the most widely used herbicides on the planet. Its popularity has been almost entirely driven by the adoption of Monsanto-engineered genetically modified (GM) crops that are resistant to the chemical.
Argentina is the world’s leading user of glyphosate, largely due to its heavy planting of GM soybeans. Yet doctors and scientists have pointed to an alarming trend of high miscarriage rates in soybean growing areas. Meanwhile, local farmers have blamed herbicides including glyphosate for alarmingly high rates of mutations in farm animals, which quadrupled following a recent surge in GM soy cultivation.
May cause uterine cancer
In the new study, researchers injected newborn female rats with glyphosate for seven days following birth, at doses of 2 mg/kg of body weight — the same dose that US regulators have ruled is safe to consume daily over the course of a lifetime.
The researchers observed abnormal cell proliferation and structural changes to the uteri of the rats, as well as disruptions to the expression of proteins that play a role in uterine development. These changes occurred even though there were no signs of toxicity (acute or chronic) in the rats, and no changes in their weight relative to untreated rats.
The findings suggest that glyphosate may harm female fertility and lead to uterine cancer, the researchers concluded.
Notably, among the effects observed were disruptions to hormonal activity (endocrine disruption), supporting growing concern that glyphosate is an endocrine disruptor. Significantly, many endocrine disruptors are more potent at very small concentrations (on the orders of parts per billion) than at the higher one typically tested by regulatory agencies.
The researchers note that they deliberately chose to use injected rather than oral glyphosate, even though oral administration is favored for pesticide and herbicide safety studies. That’s because the rats being studied were so young that they were only consuming their mothers’ milk, and there was no other way to give them the relevant doses. This decision was supported by scientists interviewed by The Ecologist; unfortunately, chemical-friendly regulators may use it as an excuse to ignore the study’s findings.
Roundup worse than glyphosate alone
Yet the new study is only one of many recent trials implicating glyphosate and Roundup in reproductive harm. Earlier this year, in a study published in Environmental Health, researchers from Kings College London found that ultra-low dose exposure to glyphosate — like humans might get from drinking water or from residue on their food — caused large-scale changes to the genome of rats. Some of these changes appear to be epigenetic — changes in gene expression that can be passed on to future generations.
The same researchers also successfully reverse-engineered the proprietary “inactive ingredients” of Roundup, and demonstrated that some of these may also have toxic effects. This is a highly significant finding, as most regulatory agencies simply presume that inactive ingredients are chemically neutral and therefore harmless.
But when it comes to Roundup, that consensus is starting to crack. Last year, an Australian study found that at levels commonly found in US and Australian drinking water, both Roundup and glyphosate alone caused endocrine disrupting effects, in part by killing off cells that produce the female hormone progesterone. That study actually found that Roundup is more toxic than glyphosate alone.
Also last year, the European Union Food Safety Authority (EFSA), while attempting to claim that glyphosate does not cause cancer, admitted that studies performed on Roundup have indeed suggested that the herbicide causes genetic damage. Thus, the EFSA said, Roundup is likely to lead to cancer.