Rats fed a lifetime diet of Monsanto's genetically engineered corn or exposed to the company's popular Roundup herbicide developed tumors and suffered severe organ damage, according to a French study released on Wednesday.

The study could have a big impact on the battle over a California ballot proposal that would require groceries containing genetically engineered ingredients to be labeled as such. Monsanto has already donated $7.1 million to the campaign to defeat the proposal, known as Proposition 37.

The study, published in a reputable American journal, links varying levels of both the Roundup herbicide and the transgenes in Monsanto’s patented NK603 corn to mammary tumors and severe liver and kidney damage.

The rats were either fed the NK603 corn alone, corn treated with agricultural levels of Roundup, or given water treated with Roundup at low levels commonly found in contaminated drinking water and used in agriculture in the United States. In each group, there were two to three more deaths compared to control groups, and the rats on the Monsanto diet died more quickly.

Gilles-Eric Séralini, a professor of molecular biology at the University of Caen who lead the research team, told reporters on Wednesday that the rats’ diet reflected the kind of exposure that humans who eat genetically engineered food should expect.

“This is around the level [that] the American population may eat, where, unfortunately GMOs are not labeled,” Séralini said. “In Europe, we have this labeling, and it helps us to avoid these compounds if necessary and promote personal choices.

The research team concluded that NK603’s transgenic traits and the endocrine-disrupting effects of Roundup herbicide could explain the results. The study is the first of its kind to link enzymes overexpressed by transgenes to health problems, Séralini said.

Endocrine-disrupting chemicals cause health problems and cancers by impacting hormonal glands in mammals and are especially dangerous to children. Pesticide and herbicide critics often fear that chemicals used to kill weeds and pests could potentially be endocrine disruptors in humans.

Monsanto’s NK603 and other varieties of corn are genetically engineered to tolerate Roundup herbicide, which contains the plant poison glyphosate and other additives, so that farmers can spray whole fields of crops to kill weeds while sparing the genetically modified corn. Genetically engineered crops are also known as genetically modified organisms, or GMO’s.

ENTIRE ARTICLE HERE: French Study Finds Tumors and Organ Damage in Rats Fed Monsanto Corn.