(Image: JR / TO; Adapted: ressaure, NedraI)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 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 among female rats compared to control groups, and the rats on the Monsanto diet tended to die 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.”

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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.

Good News for Proposition 37

“The results of this study are worrying,” said Gary Ruskin, who manages a campaign to pass the food-labeling initiative in California. “They underscore the importance of giving California families the right to know whether our food is genetically engineered, and to decide for ourselves whether we want to gamble with our health by eating GMO foods that have not been adequately studied and have not been proven safe.”

Ruskin’s Yes on Proposition 37 campaign, which is supported by organic food companies and alternative health groups, has been vastly outspent by a campaign to defeat the ballot initiative funded by millions of dollars in donations from biotech chemical companies and food manufacturers such as Monsanto, DuPont, Bayer and Nestle.

Polls taken this summer, however, show that Proposition 37 remains popular among a majority of voters despite a multimillion-dollar campaign against the initiative.

GMO Information War

A spokesperson for Monsanto told Truthout that the company will thoroughly review the data, but pointed out that scientific claims made by Séralini in regards to previous studies on rats have been refuted by a European food regulatory agency.

In the past, Séralini, an independent scientist celebrated by biotech critics, has publicly wrangled with peer scientists, pro-industry groups and regulators over interpretations of data from 90-day studies on rats conducted by biotech companies that were used to justify regulatory approvals of Monsanto crops in several countries.

Séralini and his team believe the study released this week is more conclusive because it spans two years and followed the rats’ entire lifecycle.

“It’s bizarre and dramatic for us that the US government,” said Séralini, “has not requested to make serious tests before releasing these products into the environment because these GMOs are pesticide sponges, and we know that pesticides can be harmful to humans.”

Séralini also pointed out that his team started to see tumors after four months, while the industry studies on rats were limited to a three-month period.

“It shows the genetically modified foods should be withdrawn,” said biotech critic and author Jeffrey Smith. Smith said the study further confirms reports he has heard from doctors and veterinarians who say they’ve seen their patient’s health improve after they stopped eating genetically engineered foods.

In 2010, a lead embryologist in Argentina named Dr. Andrés Carrasco survived an attacked by an angry mob determined to keep him from speaking at a public event about his own research on Roundup, which found that the herbicide caused deformations in chicken embryos that resembled birth defects in humans being reported in the country’s agricultural areas where the herbicide is heavily used.