TRADITIONAL varieties of major US food crops have been widely contaminated by DNA from genetically modified crops. Some scientists have gone as far as to suggest that this may pose a serious risk to human health.
Crops engineered to produce industrial chemicals and drugs 鈥� so-called 鈥減harm鈥� crops 鈥� could already be poisoning ostensibly GM-free crops grown for food, says a study by the Union of Concerned 快猫短视频s (UCS), based in Cambridge, Massachusetts. 鈥淚f genes find their way from pharm crops to ordinary corn, they or their products could wind up in drug-laced cornflakes,鈥� says microbiologist Margaret Mellon, the report鈥檚 co-author.
In trials, crops have been genetically engineered to manufacture antibodies to fight cancer, vaccines against rabies, cholera and foot and mouth disease, and proteins for healing wounds and treating conditions such as cystic fibrosis. But while conventional pharmaceutical factories are subject to stringent controls to prevent drugs entering the food chain or polluting the environment, no such controls exist to prevent the spread of DNA sequences from pharm crops.
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The UCS asked two commercial laboratories to test traditional varieties of three crops 鈥� maize, soybeans and canola, also known as oilseed rape 鈥� for specific sequences of DNA that have been introduced into GM varieties grown on US farms. These sequences mostly provide resistance to pesticides.
The labs reported this week that the seeds were 鈥減ervasively contaminated with low levels of DNA sequences from GM varieties鈥�. Up to 1 per cent of individual seeds contained one or more of the GM sequences, and more than half the batches of seed contained some contamination.
There is no evidence that the crops tested were unsafe, the authors say. But they fear that the story could be different when GM crops that produce drugs and industrial chemicals are more widely grown. Some seeds may already have been contaminated by pharm crops, Mellon says, and this could pose a 鈥渟erious risk to human health鈥�.
Colin Merritt, biotechnology development manager at Monsanto UK, which produces engineered crop varieties, says, 鈥淭hese levels of contamination are generally within limits set by the EU. But I do agree that with new products like pharm crops, we may need higher standards.鈥�
Concern about contamination by GM crops has focused on cross-pollination in the field (快猫短视频, 6 April 2002, p 14). But the authors believe much of the contamination has arisen from a failure to keep GM and traditional seeds apart during distribution.
The US findings are likely to inflame opinion in Europe, where governments are edging towards an accommodation with GM technology. British ministers were reported last week to have agreed to allow GM maize to be grown, although as 快猫短视频 went to press no announcement had been made.
There are no tests for DNA from industrial or pharm crops, so the researchers were unable to find out whether any crops were contaminated with it. But Jane Rissler, a plant pathologist who co-wrote the report, warns that 鈥渋t is prudent to assume that engineered sequences in any crop 鈥� including genes from crops engineered to produce drugs, plastics and vaccines 鈥� could contaminate the seed supply鈥�.
The study suggests that the DNA from GM maize that turned up on a large scale in traditional varieties of maize in Mexico (快猫短视频, 15 June 2002, p 14) is the rule rather than the exception.
A big concern, Mellon says, is that widespread contamination will undermine the value of gene banks. Many seed reserves are maintained by propagation from new seeds. But contamination could occur with each generation.
It could also undermine the strict rules for trade in GM-free and organic crops and destabilise the world patent system, since any crops carrying the sequences may, technically, only be grown if the patent holder has granted a licence.