The Environmental Protection Agency is currently reviewing the time-limited registration of all genetically engineered crops designed to produce their own insecticides. The decision on re-registration, expected in September, will have profound consequences for farmers, human health, and the environment.

Insecticide-producing plants, also known as Bt crops, are engineered to produce a toxin from the soil bacterium, Bacillus thuringiensis, in every cell. Proponents of genetic engineering claim this will reduce the currently widespread application of chemical pesticides, thus yielding an environmental boon. Their reasoning, unfortunately, contains several flaws.

Corn and cotton are the primary Bt crops grown in this country. Yet during the past five years, the percentage of field corn treated with insecticides in the U.S. has apparently remained steady, despite a significant increase in the acreage of insecticide-producing corn planted. The only study to dispute this is unpublished and was discredited in the prestigious journal ``Science'' last December as based on assumptions with tenuous conclusions.

As for cotton, the decline in insecticide applications for genetically engineered varieties is likely to be short-lived. In the 1940s, when the use of synthetic chemical pesticides began to grow rapidly, there were zero pesticide-resistant species. Today there are nearly 1,000, and the replacement of the failed one-pesticide/one-pest model with a one-gene/one-pest model only demonstrates the futility of this approach.

Beyond the simple failure to deliver promised benefits, genetically engineered varieties may also pose risks to both human health and the environment. One of the most profound and unexplored areas is the impact to soil ecosystems. Research published in 1999 demonstrated that the toxin from insecticide-producing corn is exuded out of the roots of the corn into soil, where it can bind to soil particles and remain active for at least 234 days, and possibly far longer. Yet no one is looking at the long-term impact of this on our already fragile soils.

The potential risk to monarch butterflies has received some attention in news reports, but key aspects of the story remain largely ignored.

First, such a risk should have been evaluated before 20 percent of our corn acreage was planted with insecticide-producing varieties.

Second, almost no pre-market evaluation has been done on other species, such as the endangered Karner blue butterfly. We can only wait and hope that damage has not already been done.

Finally, it's outrageous that EPA began the short public comment period on re-registration while withholding critical data on this subject.

StarLink corn, an insecticide-producing variety that was thankfully and correctly never approved by the EPA for human consumption, somehow slipped into in our food supply anyway. At least 200 people - a far higher number than usual - have recently reported suffering discomfort after eating the corn, ranging from nausea to anaphylactic shock. Companies like Aventis (the manufacturer of StarLink) that violate an agreement with EPA to keep genetically engineered varieties under tight control and then allow contamination to reach the public, should be held accountable for any harm caused.

It is true that clear and incontrovertible evidence of health risks from insecticide-producing crops does not exist; even people who got sick after eating StarLink have not yet undergone adequate testing to determine the culprit. Yet the total number of peer-reviewed studies evaluating the safety of Bt corn is zero. So no clear and incontrovertible evidence exists that these crops are safe to eat, either.

At an interagency policy meeting on the safety of genetically engineered foods organized by the U.S. Food and Drug Administration in 1988, policymakers acknowledged there was no way to be entirely certain of the safety of genetically engineered foods, saying, ``If the American public wants progress, they will have to be guinea pigs.''

Progress can come with intelligent precaution, but not with the unabashed and undeserved embrace of a largely untested and powerful technology like genetic engineering of our food.

With so many unknowns requiring further study, relating to both human health and the environment, it would be unwise for the EPA to renew the registration of insecticide-producing Bt crops. There should be a moratorium on such crops until the science is more complete. Granting the approvals now would only put the interests of biotechnology companies above the interests of the general public.

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