Environmental Health News

What's Working

  • Garden Mosaics projects promote science education while connecting young and old people as they work together in local gardens.
  • Hope Meadows is a planned inter-generational community containing foster and adoptive parents, children, and senior citizens
  • In August 2002, the Los Angeles Unified School District (LAUSD) Board voted to ban soft drinks from all of the district’s schools

#716 - Biotech: The Basics -- Part 1, 17-Jan-2001

by Rachel Massey*

Genetic engineering is the process by which genes are altered and
transferred artificially from one organism to another. Genes,
which are made of DNA, contain the instructions according to
which cells produce proteins; proteins in turn form the basis for
most of a cell's functions. Genetic engineering makes it possible
to mix genetic material between organisms that could never breed
with each other. It allows people to take genes from one species,
such as a flounder, and insert them into another species, such as
a tomato -- thus, for example, creating a tomato that has some of
the characteristics of a fish.

Starting in the 1980s and accelerating rapidly in the past
decade, companies have begun using genetic engineering to insert
foreign genes into many crops, including important foods such as
corn and soybeans.[1] Just in the past few years, genetically
engineered ingredients have begun appearing in many foods in U.S.
supermarkets; they have been detected in processed foods such as
infant formulas, drink mixes, and taco shells, to name a few
examples.[2] These foods are not labeled, so consumers have no
way to know when they are eating genetically engineered food.

Genetic engineering is an extremely powerful technology whose
mechanisms are not fully understood even by those who do the
basic scientific work. In this series, we will review the main
problems that have been identified with genetically engineered

Most genetically engineered crops planted worldwide are designed
either to survive exposure to certain herbicides or to kill
certain insects. Herbicide tolerant crops accounted for 71% of
the acreage planted with genetically engineered crops in 1998 and
1999, and crops designed to kill insects (or designed both to
kill insects AND to withstand herbicides) accounted for most of
the remaining acreage. A small proportion (under 1%) of
genetically engineered crops planted in 1998 and 1999 were
designed to resist infection by certain viruses.[4]

Genetically engineered herbicide-tolerant crops are able to
survive applications of herbicides that would ordinarily kill
them. The U.S. food supply currently includes products made from
genetically engineered herbicide-tolerant crops including
"Roundup Ready" canola, corn, and soybeans which are engineered
to withstand applications of Monsanto's Roundup (active
ingredient, glyphosate), as well as crops engineered to survive
exposure to other herbicides.[1]

Genetically engineered pest-resistant (or pesticidal) crops are
toxic to insects that eat them. For example, corn can be
engineered to kill the European corn borer, an insect in the
order lepidoptera (the category that includes butterflies and
moths). This is accomplished by adding genetic material derived
from a soil bacterium, BACILLUS THURINGIENSIS (Bt), to the
genetic code of the corn. BACILLUS THURINGIENSIS naturally
produces a protein toxic to some insects, and organic farmers
sometimes spray Bt on their crops as a natural pesticide. In
genetically engineered "Bt corn," every cell of the corn plant
produces the toxin ordinarily found only in the bacterium.

Unfortunately, genetically engineered crops can have adverse
effects on human health and on ecosystems. And by failing to test
or regulate genetically engineered crops adequately, the U.S.
government has allowed corporations to introduce unfamiliar
substances into our food supply without any systematic safety

Here are some of the reasons why we might not want to eat
genetically engineered crops:

** Ordinary, familiar foods can become allergenic through the
addition of foreign genes.

Genetic engineering can introduce a known or unknown allergen
into a food that previously did not contain it. For example, a
soybean engineered to contain genes from a brazil nut was found
to produce allergic reactions in blood serum of individuals with
nut allergies. (See REHN #638.) Allergic reactions to nuts can be
serious and even fatal. Researchers were able to identify the
danger in this particular case because nut allergies are common
and it was possible to conduct proper tests on blood serum from
allergic individuals. In other cases, testing for allergenic
potential can be much more difficult. When genetic engineering
causes a familiar food to start producing a substance previously
not present in the human food supply, it is impossible to know
who may have an allergic reaction.

** Genetic engineering has the potential to make ordinary,
familiar foods become toxic.

In some cases, new characteristics introduced intentionally may
create toxicity. The Bt toxin as it appears in the bacteria that
produce it naturally is considered relatively safe for humans. In
these bacteria, the toxin exists in a "protoxin" form, which
becomes dangerous to insects only after it has been shortened, or
"activated," in the insect's digestive system. In contrast, some
genetically engineered Bt crops produce the toxin in its
activated form, which previously only appeared inside the
digestive systems of certain insects.[5] Humans have little
experience with exposure to this form of the toxin. Furthermore,
in the past humans have had no opportunity or reason to ingest
any form of the Bt toxin in large quantities. When the Bt toxin
is incorporated into our common foods, we are exposed each time
we eat those foods.[6, pgs. 64-65.] And of course, a pesticide
engineered into every cell of a food source cannot simply be
washed off before a meal.

Toxicity can also result from characteristics introduced
unintentionally. For example, a plant that ordinarily produces
high amounts of a toxin in its leaves and low amounts in its
fruit could unexpectedly begin to concentrate the toxin in its
fruit after addition of a new gene. (See REHN #696.)

Unpleasant surprises of this sort can result from our ignorance
about exactly how a foreign gene has been incorporated into the
engineered cell. Foreign genes can be added to cells by various
methods; among other options, they can be blasted into cells
using a "gene gun," or a virus or bacterium can be used to carry
them into the target cells.[7] The "genetic engineer" who sets
this process in motion does not actually control where the new
genes end up in the genetic code of the target organism. The
"engineer" essentially inserts the genes at a random, unknown
location in the cell's existing DNA. These newly-inserted genes
may sometimes end up in the middle of existing genetic
instructions, and may disrupt those instructions.

A foreign gene could, for example, be inserted in the middle of
an existing gene that instructs a plant to shut off production of
a toxin in its fruit. The foreign gene could disrupt the
functioning of this existing gene, causing the plant to produce
abnormal levels of the toxin in its fruit. This phenomenon is
known as "insertional mutagenesis" -- unpredictable changes
resulting from the position in which a new gene is inserted.[8]
Genetic engineering can also introduce unexpected new toxicity in
food through a well-known phenomenon known as pleiotropy, in
which one gene affects multiple characteristics of an organism.
(See REHN #685.)

** Genetically engineered crops can indirectly promote the
development of antibiotic resistance, making it difficult or
impossible to treat common human diseases.

Whatever method is used to introduce foreign genes into a target
cell, it only works some of the time, so the "genetic engineer"
needs a way to identify those cells that have successfully taken
up the foreign genes. One way to identify these cells is to
attach a gene for antibiotic resistance to the gene intended for
insertion. After attempting to introduce the foreign genes, the
"engineer" can treat the mass of cells with an antibiotic. Only
those cells that have incorporated the new genes survive, because
they are now resistant to antibiotics.

From these surviving cells, a new plant is generated. Each cell
of this plant contains the newly introduced genes, including the
gene for antibiotic resistance. Once in the food chain, in some
cases these genes could be taken up by and incorporated into the
genetic material of bacteria living in human or animal digestive
systems. A 1999 study published in APPLIED AND ENVIRONMENTAL
MICROBIOLOGY found evidence supporting the view that bacteria in
the human mouth could potentially take up antibiotic resistance
genes released from food.[9] Antibiotic resistance among
disease-causing bacteria is already a major threat to public
health; due to the excessive use of antibiotics in medical
treatment and in agriculture, we are losing the ability to treat
life-threatening diseases such as pneumonia, tuberculosis, and
salmonella.[10] (See REHN #402.) By putting antibiotic resistance
genes into our food, we may be increasing the public health
problem even further.

The British Medical Association, the leading association of
doctors in Britain, urged an end to the use of antibiotic
resistance genes in genetically engineered crops in a 1999
report. "There should be a ban on the use of antibiotic
resistance marker genes in GM [genetically modified] food, as the
risk to human health from antibiotic resistance developing in
micro-organisms is one of the major public health threats that
will be faced in the 21st Century. The risk that antibiotic
resistance may be passed on to bacteria affecting human beings,
through marker genes in the food chain, is one that cannot at
present be ruled out," the Association said.[11]

To be continued.


*Rachel Massey is a consultant to Environmental Research

[1] Union of Concerned Scientists, "Foods on the Market,"
available at http://www.ucsusa.org. Choose "biotechnology" in the
bar at the bottom of the screen, then click on "Foods on the

[2] Consumers Union, "CONSUMER REPORTS: Genetically Engineered
Foods in Your Shopping Cart," Press Release, August 23, 1999.
Available at http://www.consumersunion.org/food/gefny999.htm.

[3] For one recent overview, see Environmental Media Services
Edition 1 (October 2000), available from EMS, Washington, D.C.,
(202) 463-6670 or at http://www.ems.org. Also see Pesticide
Action Network North America (PANNA), "Genetically Engineered
Crops and Foods: Online Presentation," available at

[4] Clive James, "Global Review of Commercialized Transgenic
Crops: 1999" ISAAA BRIEFS No. 12: Preview, produced by
International Service for the Acquisition of Agri-Biotech
Applications (ISAAA). Available at

[5] See Michael Hansen, "Potential Environmental and Human Health
Problems Associated with Genetically Engineered Food."
Presentation delivered at CREA International Seminar on
Transgenic Products, Curitiba, Brazil, October 11, 1999.
Available from Consumer Policy Institute, Yonkers, N.Y.:

[6] National Research Council, GENETICALLY MODIFIED
National Academy of Sciences, 2000). ISBN 0309069300.

[7] Union of Concerned Scientists, "Fact Sheet: Genetic
Engineering Techniques." Available at http://www.ucsusa.org.
Choose "biotechnology" in the bar at the bottom of the screen,
then click on "Genetic Engineering Techniques."

[8] See Food and Drug Administration, "Premarket Notice
Concerning Bioengineered Foods," FEDERAL REGISTER Vol. 66, No. 12
(January 18, 2001), pg. 4710.

[9] Derry K. Mercer and others, "Fate of Free DNA and
Transformation of the Oral Bacterium STREPTOCOCCUS GORDONII DL1
by Plasmid DNA in Human Saliva," APPLIED AND ENVIRONMENTAL
MICROBIOLOGY Vol. 65, No. 1 (January 1999), pgs. 6-10.

[10] See World Health Organization (WHO), OVERCOMING
ANTIMICROBIAL RESISTANCE (Geneva, Switzerland: World Health
Organization, 2000). Available at

[11] British Medical Association Board of Science and Education,
"The Impact of Genetic Modification on Agriculture, Food and
Health -- An Interim Statement," May 1999. Summary statement
available at http://www.bma.org.uk/public/science/genmod.htm.

Error. Page cannot be displayed. Please contact your service provider for more details. (27)