The Effect of Glyphosate Toxicity in Rats

Glyphosate, a broad spectrum herbicide marketed in brand names such as Roundup, is labeled as moderately toxic by the Environmental Protection Agency and must bear the signal word WARNING. Studies of the effects of this commonly used household product on rat pups reveal alarming results including death, but still, governmental studies conclude that glyphosate "does not result in adverse effects on development, reproduction, or endocrine systems in humans and other mammals."

History

• Glyphosate, marketed as a safe weed killer for commercial and household use, was first reported as a herbicide in 1971. It is transported into the plant via leaves and soft stalk tissue where it acts on various enzyme systems inhibiting amino acid metabolism in what is known as the shikimic acid pathway. This pathway exists in higher plants and microorganisms but not in animals. This fact is used by companies marketing glyphosate as an indicator of safety to humans.

Positive Results

• According to a Cornell University Cooperative glyphosate has no significant potential to accumulate in animal tissue because it is poorly absorbed from the digestive tract and is largely excreted unchanged by mammals. The study funded by the USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program found "at 10 days after treatment, there were only minute amounts in the tissues of rats fed glyphosate for 3 weeks. Cows, chickens, and pigs fed small amounts of glyphosate had undetectable levels in muscle tissue and fat. Levels in milk and eggs were also undetectable."

Negative Effects

• Recent studies are cause for concern about the effects of glyphosate toxicity on the male reproductive system of rats. Glyphosate reduced the testosterone production and significantly changed the progression of puberty in rats according to a study published by the Veterinary Medicine School, University of Sao Paulo in Brazil. Another study from a Brazilian University reports "in utero and lactational exposure to glyphosate, Roundup may induce significant adverse effects on the reproductive system of male Wistar rats at puberty and during adulthood."

Chronic Level Studies

• Studies show adverse effects of glyphosate toxicity in rats when exposed to high levels of the widely-used weed killer. According to the Pesticide Action Network "chronic feeding studies have shown reduced weight gain, blood and pancreatic effects, but no evidence of carcinogenicity to humans," and they site an EPA report: "Effects on pregnant mothers and foetuses included diarrhoea, decreased weight gain, nasal discharge and death of mothers and kidney and digestive disorders in rat pups." But environmental agencies insist the levels of toxicity to humans is much lower and therefore poses no health threat.

Related Concerns

• Debate continues on the environmental effects of glyphosate and the role it plays in genetically modified crops. Governmental courts and agencies and large corporate players sling lawsuits and court injunctions in the battle over Roundup Ready crops. Monsanto claims "proper stewardship" will avoid the cross-pollination potential worrying the plaintiffs. Opponents of glyphosate say its use is so extensive that it is causing habitat damage and weed resistance. The judgments will have a world-wide impact on plants and animals. Some courts have put the issue on hold until additional studies are completed.