Stranger danger

The article by the former head of the Advisory Committee on Novel Foods and Processes, Derek Burke (THES, August 14), was very revealing and profoundly worrying. He seems to have understood his duty as reassuring the public that all is well, rather than ensuring that it actually is. We hope his complacency is not shared by his successor, though from what he has recently been saying in interviews it seems likely that it is.

Burke gives no indication that he is aware of the many scientific findings - some well known, others discovered only recently - that should make us very cautious about this new technology. For example, he states confidently that "there is no reason to suppose that a gene (transferred) from a soil bacterium will escape than one of the 100,000 plant genes". This is simply not true, and it is alarming that the man who for eight years chaired the committee responsible for approving genetically modified foods should think it is.

Genes are transferred in artificial "vectors" made from viruses and other genetic parasites. The same cellular mechanisms that enable the vector to insert into the host genome may mobilise it to come out again. Secondary transfer of inserted genes from transgenic plants to soil fungi and bacteria has been demonstrated in the laboratory.

Viral DNA is found to resist digestion in the gut of mice. Large fragments enter the bloodstream and end up in white blood cells and in spleen and liver cells, in some cases linked to mouse DNA. Naked viral DNA is often more infectious than the intact virus and can give full-blown infections in hosts that are not affected by the intact virus. As many vectors used to transfer genes are made of viral DNA or contain viral promoters, they may indeed be more likely to escape than are the plant's own genes.

The same issue reported on the work of Allison Snow of Ohio State University. She has found that when transgenic oil-seed rape was crossed with a weed the result was a superweed that was not only resistant to herbicide but also, contrary to what genetic engineers had predicted, was robust. The likely consequence of planting transgenic oil-seed rape is not higher yields and less use of chemicals but the proliferation of weeds that are resistant to the herbicide and can be eradicated only by additional herbicides.

It is not enough to monitor what is happening because we may spot the problems only when it is too late to do anything We were slow to recognise the dangers to human health associated with nuclear energy, X-rays and BSE, but at least we can stop the practices responsible for the hazards. Once genes are released into the environment, there is no calling them back.

That is why so many groups and individuals have joined in a call for a five-year moratorium on the release of new genetically modified organisms. The purpose is to allow time for scientists and others to carry out research to discover where genetic engineering can deliver the goods and where the dangers outweigh possible benefits.

Mae-Wan Ho Department of biology The Open University Peter Saunders Department of mathematics King's College London