French scientists said on [September 19] that rats fed on Monsanto's genetically modified corn or exposed to its top-selling weedkiller suffered tumors and multiple organ damage. Gilles-Eric Seralini of the University of Caen and colleagues said rats fed on a diet containing NK603 - a seed variety made tolerant to dousings of Monsanto's Roundup weedkiller - or given water with Roundup at levels permitted in the United States, died earlier than those on a standard diet. The animals on the GM diet suffered mammary tumors, as well as severe liver and kidney damage. The study was published in the peer-reviewed journal Food and Chemical Toxicology and presented at a news conference in London. The researchers said 50 percent of males and 70 percent of females died prematurely, compared with only 30 percent and 20 percent in the control group. GMOs are deeply unpopular in Europe and many other countries, but dominate key crops in the United States after Monsanto in 1996 introduced a soybean genetically altered to tolerate Monsanto's Roundup weed killer. Seralini was part of a team that has voiced previous safety concerns based on a shorter rat study in a scientific paper published in 2009. This new study takes things a step further by tracking the animals throughout their two-year lifespan. Seralini believes his latest lifetime rat tests give a more realistic and authoritative view of risks than the 90-day feeding trials that form the basis of GM crop approvals, since three months is only the equivalent of early adulthood in rats.