France will push for GM ban if cancer threat confirmed
"By the beginning of the 24th month, 50-80 per cent of female animals had developed tumours in all treated groups, with up to three tumours per animal, whereas only 30 per cent of controls were affected," it said.
Males which fell sick suffered liver damage, developed kidney and skin tumours and digestive problems.
But other scientists said the study was too underpowered, had questionable gaps in the data and raised doubts more about Roundup than the NK603 corn itself.
It entailed 200 rats divided into 10 experimental groups, of which only 20 were "controls" fed ordinary corn and plain water.
This sample size is too small to rule out statistical quirks, especially as the rats were of the "Sprague-Dawley" laboratory strain, which is notoriously susceptible to mammary tumours, said Maurice Moloney, research director at Britain's Rothamsted agricultural research station.
"The first thing that leaps to my mind is why has nothing emerged from epidemiological studies in the countries where so much GM has been in the food chain for so long" Mark Tester, a professor at the Australian Centre for Plant Functional Genomics, University of Adelaide, told the news site Science Media Centre.
"If the effects are as big as purported, and if the work really is relevant to humans, why aren't the North Americans dropping like flies?! GM has been in the food chain for over a decade over there - and longevity continues to increase inexorably."