The science showed that while a toxic dose is reachable, the potential
for exposure is insignificant.
"The final consideration," Hellmich says, "is to compare
the potential for risk from using the GEO to the alternativein
this case, growing conventional varieties and spraying them with insectides.
Certainly, chemical insecticides kill many more nontargets like monarchs
than Bt corn does."
Not Spreading the Genes
Another concern widely discussed is ensuring that certain types of
transgenic plants do not spread their new genes throughout the environment.
Plant molecular geneticist David Ow, with the ARS Plant Gene Expression
Center in Albany, California, is exploring ways to manipulate the DNA
of genetically altered plants so that the transgene is deleted or inactivated
during the physiological process of pollen production.
"After all, it's not really the presence of the gene itself that's
the concern, it's what the gene will do if it spreads to unintended
hosts," he explains.
If Ow can work out an effective technique, it could help decrease the
potential for risk in all transgenic plants. "That's one of the
reasons for ARS to do this kind of work. As a federal agency, we can
allow anyone developing a transgenic plant to use the technique, because
the public benefits when we decrease risk," he says.
Another ARS plant molecular geneticist, James E. Dombrowski, with the
Forage Seed and Cereal Research Unit in Corvallis, Oregon, is approaching
the problem from a different angle. He wants to find a way to inhibit
flowering in grass and forage crops. In addition to preserving much
of a plant's nutritive value, no flowering would also mean no pollen
and no seeds, which would virtually eliminate the chance of transgene
spread. He has already identified some flowering genes in grasses.
Dombrowski believes genetic engineering has great potential benefit,
but he strongly advocates including risk assessment in transgenic research,
"especially with plants like grasses that are wind pollinated and
have the potential to cross with other plants," he says.
"We strive to have solid information about what happens with transgenic
organisms in the real-world environment, not just in the lab or under
controlled conditions. We need solid facts, like how far pollen drifts,
its fertility lifespan, and its competition level with other pollen.
Some of the data must be collected out in the fields under production
conditions to give the real picture of potential risk."
Dombrowski says the public has a legitimate right to expect scientists
to be concerned about the potential risks of transgenic crops. But,
he adds, "I believe there's a lot of unwarranted fear due to a
lack of communication. And in some cases, people aren't really thinking
the issues and arguments fully through.
"For instance, you take a gene from rye and put it into wheat
to give it resistance to a rust disease, and people are suddenly concerned
about what they're eating. But people eat seven-grain bread with wheat
and rye in it every day. And in doing so, they're already consuming
the combined DNA and proteins from both plants."
New Genes, New Allergies?
Concerns about creation of new allergens are legitimate, and checking
this out has always been part of the regulatory approval process. The
assessment of the potential for new allergens in food is integral to
the FDA process for reviewing transgenic plants.
"The public has the right to feel confident about its protection,"
says ARS molecular biologist Eliot M. Herman at the Donald Danforth
Plant Science Center in St. Louis, Missouri. "As we learn ever
more about biological systems, we can provide even more specific assurances.
Risk assessment will always be an evolving process."
On the other hand, genetic engineering can actually make a food less
allergenic. Herman did so when he created a hypoallergenic soybean variety
that should not affect the 6 to 8 percent of children and 1 to 2 percent
of adults who are allergic to soy. He used a technique called "gene
silencing" to shut down the gene that codes for the protein thought
to cause most soybean allergies in humans.
So far, Herman has tested his hypoallergenic soybean with human sera
and in sensitive animals. Testing to be sure allergens are not present
is a difficult task. He is currently working with the University of
Arkansas Medical School to develop an animal model that will allow for
very sensitive allergen testing at the biochemical and cellular level.
Such a model would be more explicit and a good addition to the feeding
trials now required.
One of the newest areas of genetic engineering is seeking to add to
the nutritional value of crops. Herman is looking for new genetic, genomic,
and proteomic methods to improve protein, oil, and nutritive value in
"While we focus on modifying crops to enhance their nutrition,
we also look at genetic expression on a global physiological basis to
detect any unpredicted negative effects," explains ARS plant physiologist
Leon V. Kochian, with the U.S. Plant, Soil and Nutrition Laboratory
in Ithaca, New York.
He points out that if genetic engineering does have negative effects,
they are most likely to be seen first in yield losses. "That would
direct us to look further at changes," he adds.
Kochian believes strongly in today's increased risk assessment. "Ten
years ago, risk assessment research was largely a responsibility of
the private sector. Increasingly, public research organizations like
ARS have been stepping in. Two important reasons are, one, that USDA
research can provide direct support for the needs of the regulatory
agencies and, two, that many crops now being genetically engineered
are small-market crops, such as fresh fruits. The reasons for making
these crops pest resistant and reducing pesticide use are compelling,
but companies are reluctant to pursue them because the small amount
of acreage involved in growing these crops may preclude profitability."
Not Just Plants
Plants, of course, are not the only life forms that have been genetically
engineered. Livestock, insects, and microorganisms are being genetically
tailored for traits that cannot otherwise be easily bred in.
ARS animal physiologist Robert J. Wall with the Biotechnology and Germplasm
Laboratory in Beltsville, Maryland, led the collaborative team that,
in 2000, succeeded in adding genes for mastitis resistance to a cloned
Jersey cow. He served as a subject matter specialist in the USDA Biotechnology
Risk Assessment Grants Program workshop on research needs and priorities
for animals last year.
"A major difference in risk assessment for genetically engineered
farm animals is that we don't have the same worries about transgenes
escaping from them as we do with plants," Wall explains. "But
we still need to make sure the meat and milk are safe to eat."
The type of risk assessment needed is really determined by the kind
of genes that have been added. "If what you add to a Hereford is
an extra copy of a bovine growth hormone gene so that muscling is increased,
that'll need a lot less testing than adding bacteria genes that don't
exist in the cow naturally," Wall says.
"And if the genes are for a product that's broken down in people's
stomachs, that too will change the nature of the risk assessment. But
the public is entitled to know that we have considered the risks in
whatever we are engineering."
That's the key to the future of genetically engineered organisms: The
public must know that researchers have competently assessed any risk
and that safety has been ensured.By J.
Kim Kaplan, Agricultural Research Service Information Staff.
This research is part of Plant Biological and Molecular Processes,
an ARS National Program (#302) described on the World Wide Web at www.nps.ars.usda.gov.
To reach scientists mentioned in this story, contact Kim
Kaplan, USDA-ARS Information
Staff, 5601 Sunnyside Ave., Beltsville, MD 20705-5128; phone (301)
504-1637, fax (301) 504-1648.