Crops Widely Contaminated by Genetically-Modified DNA
US scientists are warning of a potentially "serious risk to human health" after the discovery that traditional varieties of major American food crops are widely contaminated by DNA sequences from GM crops.
Crops engineered to produce industrial chemicals and drugs-so-called "pharm" crops-could already be poisoning ostensibly GM-free crops grown for food, warns the study by the Washington-based Union for Concerned Scientists, released last month.
"If genes find their way from pharm crops to ordinary corn, they or their products could wind up in drug-laced corn flakes," says the report's co-author, UCS microbiologist Margaret Mellon.
In trials, crops have been genetically engineered to manufacture proteins for healing wounds and treating conditions such as cystic fibrosis, cirrhosis of the liver and anaemia; antibodies to fight cancer and vaccines against rabies, cholera and foot-and-mouth disease. Conventional drugs manufacture is subject to stringent controls to prevent them entering the food chain or contaminating the natural environment. But there are currently no such controls to prevent the spread of DNA sequences from pharm crops.
The UCS asked two commercial laboratories to test traditional varieties of three crops-maize, soybeans and canola or oil-seed rape-for specific sequences of DNA that have been introduced into GM varieties currently grown on US farms. The sequences studied mostly give resistance to proprietary pesticides.
The labs reported that the seeds were "pervasively contaminated with low levels of DNA sequences from GM varieties". Up to 1 per cent of individual seeds, and more than half the batches of seeds, contained one or more of the GM sequences.
There is no evidence that the crops tested were unsafe, say the authors. But they fear this may not be true for second-generation GM crops that contain DNA sequences that manufacture drugs and industrial chemicals.
"Seed contamination is the back door to the food supply," says Mellon. "The realisation that some seeds may already have been contaminated [by pharm crops] is alarming" and could pose a "serious risk to human health".
Until now concern about GM contamination has focused on cross-pollination in the field. But the authors guess that much of the contamination has arisen from a failure to keep GM and traditional seeds apart during manufacture and distribution.
The tests did not discover any crops contaminated with sequences from pharm or industrial crops because there are no current tests for them. But co-author and plant pathologist Jane Rissler warns: "Until we know otherwise, it is prudent to assume that engineered sequences originating in any crop-including genes from crops engineered to produce drugs, plastics and vaccines - could potentially contaminate the seed supply."
NewScientist.com news service
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