How Safe Are Genetically-Engineered Crops?

Townsend Letter for Doctors and Patients,  Oct, 2001  by Jule Klotter

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The biotech industry claims that its genetically-engineered crops produce higher yields with less damage to the environment due to pesticides. It also claims that these crops pose no risk to health. An article distributed online by the Lightparty refers to numerous studies that contradict these claims. Studies have shown that the use of genetic material to make soybeans resistant to Roundup Ready pesticide causes a decrease in the yield of about 4% when compared to conventional soybeans. In one review of 8200 university-based yield trials for 1998, C. Benbrook found a mean yield loss of 3.1 bu/ac or 5.3% in Roundup resistant varieties. In the case of corn, GMO varieties do show a higher yield than conventional strains, but this does not translate into an economic advantage for the farmer. M. Duffy and L. Miller of Iowa State University reported that yields of GMO corn were higher than conventional corn during 1998, but costs to the farmer were also higher when using the biotech crop. Also, the market for GMO crops has decreased, reducing profits.

In Bt corn, the entire plant has been engineered to contain the pesticide Bt. Bt, a bacteria, has been used judiciously by farmers for many years to kill European cornborers. Monsanto, the manufacturer of Bt corn, claims that its GMO product "reduced or eliminated the use of broad spectrum chemical insecticides on some 15 million acres of US farmland" in 1998. The Lightparty article says that "only a tiny fraction of corn acreage is treated with insecticides at all...most insecticides are used for rootworms and soil insects [and applied at planting], not European cornborer." Widespread planting of Bt corn, which contains the insecticide in all parts of the plant which includes its leaves and pollen, have affected many insects, including beneficial ones. Insects that survive the pesticide, especially the cornborer, pass their resistance on to future generations. Resistance to Bt is developing more quickly than anticipated.

Although neither biotech researchers and companies nor the government recognize a difference between conventional and biotech crops, farm animals do. An article by S. Sprinkel (When the corn hits the fan, Acres, USA Special Report 18, September 1999) reports several cases in the Midwest in which "...cattle refused to graze Bt-corn stubble, hogs went off feed when GE grains were included in the ration, cattle stopped eating when switched to GE silage, rate of gain dropped when switched to GE feed, and cattle broke through a fence and walked through RR-corn to mow down a non-GE hyybrid, leaving the RR-corn untouched." Also in 1999, the British Medical Asociation called for "an open-ended moratorium on the planting of GM crops, a ban on releasing GMOs into the environment, and review of the World Trade Agreement to ensure that human health and safety take precedence over global trade in foodstuffs and seed."

Because GMO technology uses antibiotic-resistant marker genes, the medical association is concerned that the property of antibiotic-resistance will transfer to bacteria already found in the body, such as E. coli. Transgenes, used by the biotech industry, easily move across species barriers -- which is why a fish gene can be implanted into a tomato. Plasmids, which are used to insert transgenes into chromosomes, have integrated into the DNA of laboratory rat intestinal, spleen, and liver cells that eat GMO food, according to research performed by W. Doerfler and R. Schubbert [Wener Klinische Wochenschrift (1998). 110/2:40-44). Further, these plasmids have crossed the placental barrier and entered the DNA of embryonic rats [R. Schubbert et al. On the fate of orally ingested foreign DNA in mice: chromosal association and placental transmission to the fetus. Mol. Gen. Genet. 259: 569-576].

"Ten Reasons why farmers should think twice before growing GE craps" Lightparty@aol.com, September 30, 2000.

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