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THE tests that the US government relies on to keep foods free from
genetically modified contaminants can miss low levels, claims a controversial
research paper by the Iowa company Genetic ID.

The tests in question use antibodies to detect the presence of GM foods. But
the companies making such tests claim the report is an attempt by Genetic ID to
promote the technique it uses.

Genetic ID prepared samples of soybean containing between 0.1 and 10 per cent
GM beans, and sent them to official testing labs. Of the samples with a GM
content of less than 1 per cent, more than 30 per cent were incorrectly
identified as GM-free.

The company says it also has unpublished evidence that there are similar
problems with the detection of Starlink maize, a GM strain not approved for
human consumption because of fears that it may trigger allergies. At least one
shipment of maize destined for Japan—which prohibits even traces of
unapproved GM foods—was cleared by the US only to fail Japanese tests.

Genetic ID’s researchers say their work argues that antibody tests should be
supplemented by the technology the company uses, the polymerase chain reaction
(PCR) method, which detects modified DNA directly. But critics disagree: “This
isn’t good science,” says Dean Layton of EnviroLogix in Portland, Maine, which
produces an antibody test for Starlink. “It is a transparent attempt to
undermine the competition.”

Genetic ID’s report admits that the antibody tests are reliable if carried
out properly, Layton says. And he points out that the labs that took part were
told that the tests should be performed as they are “routinely used”. Labs do
not generally test for levels less than 1 per cent for soybeans. So if the labs
usually test for a 5 per cent level—an acceptable level for soybean
exports to Japan—it’s no surprise they failed to detect a 1 per cent
level. All the labs reliably detected samples with a 10 per cent GM content.

Don Kendall of the US Department of Agriculture says the USDA’s quality
assessment of its own labs showed that the tests are being used correctly. In
response to Genetic ID’s report, however, it is investigating further. But
Kendall doesn’t expect policy to be changed to include the use of PCR. “It is
too expensive and too slow,” he says.