The first animal feeding trial studying the lifetime effects of exposure to Roundup tolerant GM maize and Roundup, the world's best-selling weed killer, shows that levels currently considered safe can cause tumors and multiple organ damage and lead to premature death in laboratory rats, according to research published online by the scientific journal Food and Chemical Toxicology.

Researchers found that rats, fed on a diet containing NK603 Roundup tolerant GM maize, or given water containing Roundup at levels permitted in drinking water and GM crops in the US, died earlier than rats fed on a standard diet. They suffered mammary tumors and severe liver and kidney damage.

The paper reports on a study conducted by a team of scientists led by molecular biologist and endocrinologist Prof. Gilles-Eric Seralini, co-director of the Risk Quality and Sustainable Environment Unit at the Univ. of Caen, France, who is an authority on studies into the health impact of GMO's and pesticides. It was supported by independent research organization, CRIIGEN.

In the peer reviewed paper, the research team says they believe this is the first long-term animal feeding trial to examine the effects of Roundup, the world's most used herbicide, and a commercial Roundup tolerant GM maize. Researchers studied 10 groups, each containing 10 male and 10 female rats, over their normal lifetime - two years.

Three groups were given Roundup in their drinking water, at three different levels consistent with exposure through the food chain from crops sprayed with the weed killer: the mid level corresponded to the maximum level permitted in the US in some GM feed; the lowest corresponded to contamination found in some tap waters. Three groups were fed diets that contained different proportions of NK603 – 11 percent, 22 percent and 33 percent. Three groups were given both Roundup and NK603 at the same three dosages. The final control group was fed an equivalent diet with no Roundup or NK603 but containing 33 percent of equivalent non-GM maize.

Researchers found that NK603 and Roundup both caused similar damage to the rats' health whether they were consumed on their own or together. Females developed fatal mammary tumors and pituitary disorders. Males suffered liver damage, developed kidney and skin tumors and experienced problems with their digestive system. The team also identified a "threshold effect" where even the lowest doses were associated with severe health problems.

The report states, "Similar degrees of pathological symptoms were noticed in this study to occur from the lowest to the highest doses suggesting a threshold effect. This corresponds to levels likely to arise from consumption or environmental exposure, such as either 11 percent GM maize in food, or 50ng/L of glyphosate in R-formulation [the lowest concentration of Roundup in the rats' drinking water] as can be found in some contaminated drinking tap waters, and which falls within authorized limits."

Up to 50 percent of males and 70 percent of females died prematurely (before deaths could be put down to normal aging) compared with only 30 percent and 20 percent in the control group.

Across all treatments and both sexes, researchers found treated rats developed 2-3 times more large tumors than the control group, defined as 17.5mm in females and 20mm in males.

By the beginning of the 24th month 50 -80 percent of females in all treated groups had developed large tumors, with up to three per animal. Only 30 percent of the controls were affected.

The tumors "were deleterious to health due to a very large size," making it difficult for the rats to breathe, causing problems with their digestion and resulting in hemorrhaging.

The first large detectable tumors appeared after four and seven months in males and females respectively but only after 14 months in the female control group and 23 months in a control male. However, the majority of tumors were only detectable after 18 months.

Treated males suffered severe liver and kidney dysfunction. Liver congestions and necrosis were 2.5-5.5 times higher than in the control group. There were also 1.3–2.3 times more instances of "marked and severe" kidney disease.

The lowest dose tested in the study (50 nanograms per liter) is below safety limits for glyphosate in water and crops. EU legislation sets the Maximum Residual Level (MRL) in water at 0.1 mg/liter, 1 mg/kg in maize and 20mg/kg in other animal feeds like soy, oats and barley. The US sets an MRL in some animal feed of 400mg/kg.

The research findings raise serious questions about the current regulatory process for licensing industrial chemicals, pesticides and other novel crops. The scientists observe that GM crops have been approved safe for consumption on the basis of 90-day animal feeding trials. They also point out that only Roundup's active principle, glyphosate, has been tested rather than the commercial product, which includes ingredients that enable the glyphosate to penetrate plants more efficiently.

The research also highlights the urgent need for more research into the long-term effects of all GM food crops, which are currently grown on 1.8 percent of the world's agricultural land. In the US, 70 percent of processed foods contain GM ingredients without GM labeling and 85 percent of maize now grown in the U.S. is GM. In the UK and Europe, GM maize is not consumed directly by humans but it is widely included in animal feed. Hundreds of thousands of tons of GM maize are imported to the UK each year for use in the diets of chickens, pigs and dairy cows. Meat and dairy products from animals fed on GM are currently sold in British supermarkets without any requirement for GM labeling. 

The researchers hypothesize that the reason why NK603 GM maize, NK603 sprayed with Roundup and Roundup on its own, all produced very similar negative health outcomes, is that both the GM maize and the weed killer Roundup "may cause hormonal disturbances in the same biochemical and physiological pathway."

Glyphosate, the active ingredient in the herbicide Roundup is a known endocrine disruptor, and previous research has shown that it can cause liver and kidney failure if consumed above maximum permitted residue levels. However, this is the first research that suggests that even very low levels, such as those found in drinking water, are harmful when consumed over an extended period.

The paper says, "The results of the study presented here clearly demonstrate that lower levels of complete agricultural glyphosate herbicide formulations, at concentrations well below officially set safety limits, induce severe hormone-dependent mammary, hepatic [liver] and kidney disturbances."

It suggests that overexpression of the GM "transgene" EPSPS, which makes NK603 tolerant to Roundup in the field, may disrupt biosynthetic pathways and cause similar problems. Most edible GM crops use EPSPS to make them tolerant to Roundup.