September, 2004
Source:
September 2004 issue of Agricultural Research magazine.
Forum: How safe are genetically
engineered crops?
A lot of
people around the world want to know the answer to the question
posed in the title.
Here in the United States,
genetically engineered (GE) crops have been grown on a large
scale since the mid-1990s, with documented reductions in
insecticide use and production costs. No discernible ill effects
have shown up to offset these benefits. Not only that, but
science promises a tremendous array of future advances, such as
improved nutritional balance, elimination of trans fats, and
enhanced disease resistance and cold tolerance.
So, what's the problem? With this
relatively new technology of genetic engineering, naturally
there are questions the public has never considered before, and
people want some answers before they accept it. Some questions
are obvious and have been thoroughly researched. For example,
are these crops safe to humans and other species that inhabit
Earth? Scientists measure the degree of safety by posing the
question, "What is the risk?" Hence the origin of the science of
risk assessment.
Risk is never perfectly
controlled. Every activity in life carries some degree of risk.
For example, we know that there were 42,815 highway fatalities
in the United States in 2002, but we still get into our cars
because we are familiar with that risk and we accept it for the
benefits that our cars bring us.
Similarly, crops bred
conventionally may carry risks, such as allergic reactions, but
again we accept the risks. We also accept that some foods are
riskier than others, and while we may handle them with more
care, we still eat them.
Risk assessment basically consists
of providing the answers to three questions: What can go wrong?
How likely is it? How bad would it be? Risk analysis examines
the answers and compares them to various alternatives so that
the least risky pathway can be followed (risk management). Risk
assessment is science. Risk management is art. It depends on the
values and experiences of a society, which then decides which
types and degrees of risks are acceptable and which are not.
This is where
USDA/ARS research comes in. Research provides answers to the
risk assessment questions. The answers may differ greatly
depending on circumstances. For example, if genetic engineering
simply moves a gene for a common food ingredient from one safe
food crop to another, this does not expose consumers to new
components in their food supply. The added risk to food safety
is very small. But if a genetically engineered plant contains a
pharmaceutical or other new compound that must be kept out of
the food supply, the answers could be very different.
This is why ARS committed $24
million in fiscal year 2004 to biotechnology risk assessment and
risk mitigation research, an increase of more than $8 million
compared to fiscal year 2002. The research covers many topics,
from assessing allergenicity of GE foods to blocking the
movement of genes from GE crops to non-GE crops in the field.
The story on page 4 gives a more in-depth look at this research.
Part of the reason for ARS to
carry out risk assessment research is to provide data on the
transgenic products of its own research projects. But there is
more to it than that. ARS is supported by public tax dollars,
and it takes on issues important to the public good that can't
be done elsewhere. For example, ARS is monitoring insect
resistance to Bt on behalf of the Environmental
Protection Agency. (Some crops have been genetically engineered
to contain Bt, a bacterium that controls certain insect
pests.) It's a long-term, continuous effort that's national in
scope and best done by a single organization. Data will be drawn
from the Bt crop varieties of multiple seed companies, so
it isn't research that a single company could carry out.
What happens when research detects
a significant risk? If the product is important and there is no
other way of producing it, then research to reduce risk is
appropriate. ARS is developing several tools to decrease or
eliminate some of the risks that might be associated with
transgenics. For example, if a plant needs protection against a
leaf-feeding pest, the protective agent need not also be present
in the grain (that's harvested for food). The first defense
against risk is to choose safe genes well and carefully and
prove their suitability. A second line of defense is a risk
mitigation strategy, in this case blocking accumulation of the
new material in the grain. The technology to direct synthesis of
these agents, such as Bt, to specific tissues is known
and under development but not yet perfected.
ARS is not alone in carrying out
risk assessment research. Companies that produce genetically
engineered seeds or genes collect a lot of specific information
about their products to prove safety. The public sector (USDA
and state universities), however, generally takes a broader
approach, attempting to bring out principles and issues beyond
specific products. In addition to ARS's in-house research, USDA
funds a competitively awarded grants program for research on
biotechnology risk assessment. That program focuses on
environmental risk and is supported by a 2-percent levy on all
biotechnology research funded by USDA.
The aim of all this research is to
provide useful and important agricultural products to feed and
clothe the world—now and well into the future. If genetic
engineering is to fulfill its potential, it must be the safest
way to meet that lofty goal. Moreover, it must be accepted as
such by the public that eats the food. Until both those goals
are reached, our work is not done.
John W. Radin
ARS National Program Leader
Plant Physiology and Risk Assessment
Beltsville, Maryland
"Forum" was published in the
September 2004 issue of Agricultural Research
magazine.
USDA/ARS leads in assessing risk in transgenics
Since before Mary Shelley
published "Frankenstein" in 1818, people have oscillated between
concern that what scientists create in the lab will be dangerous
and hope that research progress will improve their lives.
But few scientific advances have
created a wider spectrum of public debate than genetic
engineering of living organisms. Many people see the importance
of the technology and believe it is essential for developing new
and improved agricultural products. Others object to genetic
engineering on philosophical grounds or worry about the risks a
genetically engineered organism (GEO) could present to people or
the environment.
Some people feel that scientists
have not paid enough attention to potential risks. If GEOs are
to maintain and increase their acceptance as new traits are
introduced into more and more species, risk must continue to be
clearly and openly assessed.
The assessment of safety data is
integral to the regulatory process of the three primary federal
agencies responsible for regulating GEOs: USDA's Animal and
Plant Health Inspection Service, the U.S. Environmental
Protection Agency (EPA), and the Food and Drug Administration
(FDA). Advances in our methods of carrying out genetic
engineering and in our understanding of physiological and
ecological processes allow scientists to maintain sophisticated
and state-of-the-art procedures and controls for ensuring the
safety of GEOs before they're allowed to be commercially raised.
There's no question that GEOs are
becoming essential to agriculture by making new traits
available, helping agriculture be more environmentally
sensitive, and reducing production costs. To remain competitive
and environmentally sensitive, farmers need traits such as the
insect and herbicide resistance offered only by transgenic
crops.
For all these reasons,
ARS has become a
leader in biotechnology risk assessment research.
"For the past 4 or 5 years, ARS
has coordinated and carried out more and more biotechnology risk
assessment research and directed more resources into this work,"
says John W. Radin, ARS national program leader for plant
physiology and risk assessment. "We've always done some research
in this area, but today it's a very high priority."
There are several areas of risk
assessment that ARS is uniquely suited to study: creating more
specific ways to transfer only desired genes, developing new
models for doing risk assessments, finding ways to limit spread
of transgenes, discovering ways to prevent new allergens from
being created, ensuring that nontarget organisms are not put at
risk by a GEO, and carrying out long-term monitoring to spot any
emerging resistance to transgenic traits.
Making Sure Resistance Is Futile
Cotton was one of the first crops
to benefit from laboratory genetic engineering. Genes from the
bacterium Bacillus thuringiensis (Bt) were added
to cotton, making the plant produce a protein toxic to several
major cotton pests, including pink bollworm, tobacco budworm,
and bollworm. Control of such pests had previously necessitated
massive amounts of pesticide use.
Since EPA approved its release in
1995, Bt cotton has been extremely successful in the
United States and other countries such as China, India, and
Australia. In 2001, transgenic varieties generated an additional
$235.6 million in revenue for farmers while reducing pesticide
use by 8 million pounds, according to a study by the National
Center for Food and Agricultural Policy.
But there's concern that
widespread growing of Bt cotton may lead to insects
developing resistance to Bt proteins, thereby canceling
out one of the most potent but more environmentally friendly
antipest tools. Resistance to foliar-applied Bt has shown
up in Indianmeal moths, diamondback moths, and at least nine
other insects.
So, even though there's been no
indication of resistance being generated by Bt cotton,
EPA requested that monitoring studies be done. Each year,
samples of insects are collected in fields all over the Cotton
Belt and sent to the ARS Southern Insect Management Research
Unit in Stoneville, Mississippi.
"ARS is the perfect agency for
conducting such a long-term, widespread monitoring study that
will pick up the first signs of any insect resistance," says
John Adamczyk, who, along with Carlos Blanco, coordinates the
effort. Both are ARS entomologists.
"ARS is national in scope, which
helps when you are running a program that needs to extend from
Virginia to Texas," Adamczyk explains. "We're even working on
making this an international program, since the insects migrate
from Mexico as well."
But perhaps most importantly, he
adds, ARS is an unbiased source of data. The agency has no
financial stake involved if transgenic cotton is found to be
creating a risk of insect resistance.
"We report our results every year, and if we ever do start
finding resistance, the industry is reassured that we have no
agenda to simply take a technology away," says Adamczyk. While
the impetus for resistance monitoring came from industry's need
to provide EPA with data, Adamczyk sees the program as serving a
wider audience. "We're providing a service to a
$10-billion-a-year agricultural industry, but we are really
protecting the public and the environment."
The group is also developing
better methods that may serve as models for resistance
monitoring in conventional pest controls as well as in
transgenic crops.
"We're also working on identifying
genes that may control insect resistance to Bt," Adamczyk
says. "If we can develop better information about that, we may
be able to predict resistance very early—before we lose the
effectiveness of Bt. Such a warning may allow us to do
something about it in time."
No Risk to Monarchs
ARS's ability to be the objective
voice, not beholden to any one group's agenda, allows the agency
to work well with everybody. When a letter published in the May
1999 issue of Nature suggested that Bt corn
threatened monarch butterflies, ARS was able to quickly
coordinate groups with widely differing positions on GEOs to
develop verifiable, sound, scientific data before any decisions
were made, despite an initial flurry of media coverage and
public concern.
The concern was that monarch
caterpillars eat only milkweed leaves, which sometimes grow in
and around cornfields, and that Bt corn pollen falls on
the milkweed leaves a short time each year.
"Groups from the Union of
Concerned Scientists to the Biotechnology Industry Organization,
from universities to Monarch Watch, were willing to work with
ARS to ensure we really did find out what risk, if any, Bt
corn was to a nontarget insect like the monarch butterfly," says
ARS entomologist Richard L. Hellmich. He's in the Corn Insects
and Crop Genetics Research Unit in
Ames, Iowa.
How the issue was handled is being
seen as a model for nontarget risk assessment research. First,
the primary questions were researched. One: What dose of Bt
protein from the transgenic corn varieties is actually toxic to
monarch caterpillars? Two—and just as important: What are the
chances that the caterpillars will actually be exposed to that
dose?
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 alternative—in 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
soybeans.
"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.
Genetic Engineering Timeline
You can date the history of
genetic engineering several ways, considering how long people
have been manipulating genes.
8000 B.C.—Humans
domesticate crops and livestock and begin selecting for superior
traits.
1863 A.D.—Gregor
Mendel discovers traits are inherited through discrete,
independent units (genes) and in specific, predictable patterns.
1906—Term
"genetics" is introduced.
1919—First
use of the word "biotechnology" in print.
1933—Hybrid
corn is commercialized, eliminating the option of saving seeds.
Remarkable yields outweigh increased costs of annual seed
purchases, and by 1945, hybrid corn accounts for about 78
percent of U.S.-grown corn.
1941—Term
"genetic engineering" is first used by Danish microbiologist A.
Jost in a lecture on reproduction in yeast in Lwow, Poland.
1946—Discovery
that genetic material from different viruses can be combined to
form a new type of virus, an example of genetic recombination.
1973—Stanley
Cohen and Herbert Boyer perfect techniques to cut and paste DNA
(using restriction enzymes and ligases) and reproduce the new
DNA in bacteria.
1980—U.S.
Supreme Court rules that genetically altered life forms can be
patented and allows Exxon to patent an oil-eating microorganism.
1981—ARS
develops foot-and-mouth disease vaccine—the first effective
subunit vaccine for any animal or human disease using gene
splicing.
1982—Genentech,
Inc., receives approval from FDA to market genetically
engineered human insulin.
1984—First
transgenic farm animals—sheep and pigs—are born.
1986—EPA
approves release of the first genetically engineered crop,
gene-altered tobacco.
1987—ARS
develops microinjection technique to move a whole chromosome
into a single cell of another plant.
1991—ARS
develops gene-deletion technology to remove antibiotic
resistance genes.
1994—FDA
approves Flavr Savr tomato, the first genetically engineered
food.
1995—Bt
cotton and Bt corn get first EPA approval; registration
was renewed in 2001.
"ARS Leads in Assessing Risk in
Transgenics" was published in the
September 2004 issue of Agricultural Research magazine. |