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Executive Summary
In late 1988, the Biotechnology Science Coordinating Committee
(BSCC), representing the U.S. Department of Agriculture, Environ-
mental Protection Agency, National Institutes of Health, National
Science Foundation, ~d Food and Drug Administration, asked the
National Academy of Sciences-National Research Council (NRC) to
evaluate scientific Formation pertinent to making decisions about
the introduction of genetically modified rrucroorganisms and plants
into the environment. The NRC was asked to use this analysis to
identify criteria for defining risk categories and to recommend ways
to assess the potential risks associated with introducing these mod-
ified organisms. A steering committee was formed under the Board
on Biology of the NRC's Commission on Life Sciences to prepare a
report responding to the BSCC request. The steering committee,
with overalD responsibility for preparing the report, was augmented
by two subcomrn~ttees of experts, one for microorganisms and the
other for plants.
The committee considered the foci of its work to be:
plants and microorganisms, but not animals;
introductions under field-test conditions typical of those cur-
rently being proposed, but not large-scare commercial am
plications and the scientific, economic, ethical, and societal
issues associated with large-scale applications;
1
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environmental effects excluding human health effects;
scientific issues primarily, not regulatory policy matters;
field-test conditions only in the conterminous United States in
recognition that domesticated and wild species are different
in other countries and areas of the world;
general procedures for determining categories of risk for in-
troductions, not recommendations for specific cases.
The steering committee and subcommittees adopted the funda-
mental principle enunciated in the document reintroduction of Re-
combmant DNA-Engineered Organisms into the Environment: Key
Issued (NAS, 1987) that safety assessment of a recombinant DNA-
modified organism "should be based on the nature of the organism
and the environment into which it will be introduced, not on the
method by which it was modified. The principle that evaluation
should be of the product and not the process by which the product
is obtained is reemphasized in Chapter 2 of this report. The d~scus-
sion also points out that although genetic modification by molecular
methods may be more powerful and capable of producing a wider
range of phenotypes, "no conceptual distinction exists between ge-
netic modification of plants and microorganisms by classical methods
or by molecular methods that modify DNA and transfer genes.
The section of the report on plants (Chapters 3-6) discusses the
relevant biological properties of genetically modified plants. It also
describes past experience with genetic modification and introductions
of plants modified by classical and by molecular genetic methods.
The major environmental issue of potential weediness receives specie
attention in the report.
The section of the report on microorganisms (Chapters 7-11)
discusses the properties of the genetic modification, phenotypic prop
erties of the source organism and its genetically modified derivatives,
and properties of the environment with respect to the organisrrm that
may be released into it.
Investigators modifying microorganisms for environmental mtrm
auction should assess the influence of genetic alteration on the or-
gan~sm's phenotype and the mobility of the altered trait. It is highly
unlikely that moving one or a few genes from a known pathogen
to an unrelated nonpathogen wall confer pathogenicity on the ret
cipient. If the recipient is itself a pathogen, increased virulence for
particular hosts may result. If modifications of this latter type are
contemplated, special attention must be paid to them. In some cases
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persistence is not desirable and uncertainty exists about the microor-
ganism's eEects on the immediate environment. When assessing risk
in these cases, the most relevant phenotypic properties relate to the
persistence of the microorganism and its genetic modification. Eval-
uation of phenotypic properties raises questions about the fitness
of the genetically modified microorganism, the potential for gene
transfer from the introduced microorganism, the tolerance of the
introduced microorganism to physicochemical stresses, its competi-
tiveness, the range of substrates available to it and, if applicable, the
pathogenicity, virulence, and host range of the introduced microor-
ganism.
The report discusses the long history of utility and safety in
the use of plants and microorganisms. Society has benefited greatly
from the use of genetically modified microorganisms and plants, aunt
field testing is essential if we are to increase our knowledge about
the relative safety or risk of large-scale use of genetically modified
organisms and to determine the potential utility of the modified
organisms.
Other major scientific conclusions are as follows:
PLANTS
1. Plants modified by classical genetic methods are judged safe
for field testing on the basis of experience with hundreds of millions
of genotypes field-tested over decades. They are, ~ the terms used
by the plant subcomrn~ttee, Unmanageable by accepted standards."
The committee emphasizes that the current means for making de-
cisions about the introductions of classically bred plants are entirely
appropriate and no additional oversight is needed or suggested in this
report.
2. Crops modified by molecular and cellular methods should
pose risks no different from those modified by classical genetic meth-
ods for similar traits. As the molecular methods are more specific,
users of these methods waif be more certain about the traits they
introduce into the plants. Waits that are unfarn~liar ~ a specific
plant wait require careful evaluation ~ smaD-scale field tests where
plants exhibiting undesirable phenotypes can be destroyed.
3. At this time, the potential for enhanced weediness is the
major environmental risk perceived for introductions of genetically
modified plants. The likelihood of enhanced weediness is low for
genetically modified, highly domesticated crop plants, on the basis
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of our knowledge of their morphology, reproductive systems, growth
requirements, and unsuitability for sel£perpetuation without human
intervention.
4. Confinement ~ the primary condition for ensuring safety of
field introductions of cIassicaDy modified plants.
5. Depending on the crop species, proven confinement options
include biological, chern~cal, physical, spatial, environmental, and
temporal isolation, as wed as size of field plot.
6. Plants grown within field confinement for experimental pur-
poses rarely, if ever, escape to cause problems in the natural ecosys-
tem.
7. Established confinement options are as applicable to field
introductions of plants modified by molecular and cellular methods
as to introductions of plants modified by classical genetic methods.
MICROORGANISMS
1. The precision of many of the molecular methods allows sci-
entists to make genetic modifications in microbial strains that can
be fully characterized, in some cases to the determination of specific
alterations of bases in the DNA nucleotide sequence.
2. The molecular methods have great power because they en-
able scientists to isolate genes and to transfer them across biological
barriers.
3. Although field experience provides considerable information
about some rn~croorganisms- for example, rhizobia, mycorrhizae,
and many plant pathogens and biocontro! agents-~ general, infor-
mation regarding the ecology of microorganisms and experience with
planned environmental introductions of genetically modified m~croor-
ganisms is limited compared with that regarding plants. However,
no adverse effects have developed from introductions of genetically
modified microorganisms. Ecological uncertainties can be addressed
scientifically with respect to genetic and phenotypic characterization
of the microorganisms as well as by consideration of environmen-
ta] attributes such as nutrient availability. Field tests of genetically
modified organisms can go forward when sufficient information exists
to permit evaluation of the relative safety of the test.
4. The likelihood of possible adverse effects can be minimized
or eliminated by appropriate measures to confine the introduced rn~-
croorganism to the target environment, for example, by introducing
Suicide genes, as they become practicable, into the organisms.
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F~M1DWORE
The committee developed a framework for the evaluation of risk
based on criteria that are summarized below and detailed in Chapters
6 and 11.
Are we familiar with the properties of the organism and the
environment into which it may be introduced?
Can we confine or control the organism effectively?
What are the probable effects on the environment should the
introduced organism or a genetic trait persist longer than
intended or spread to nontarget environments?
When the familiarity standard for a plant or microorganism has
been satisfied such that reasonable assurance exists that the organism
and the other conditions of an introduction are essentially similar
to known introductions, and when these have proven to present
negligible risk, the introduction is assumed to be suitable for field
testing according to established practice.
The familiarity criterion is central to the suggested framework
of evaluation. Its use per~ruts decision-makers to draw on past ex-
perience with the introduction of plants and m~croorg~isms into
the environment, and it provides future flexibility. As field tests are
performed, information wall continue to accumulate about the or-
ganisms, their phenotypic expression, and their interactions with the
environment. Eventually, as our knowledge increases, entire classes
of introductions may become familiar enough to require minimal
oversight.
Familiar does not necessarily mean safe. Rather, to be familiar
with the elements of an introduction means to have enough ~nforma-
tion to be able to judge the introduction's safety OF risk.
When knowledge of the type of modification, the species being
modified, or the target environment ~ insufficient to meet the fa-
m~liarity criteria, the proposed introduction must be evaluated with
respect to the ability to confine or control the introduced organism
and to the potential effects of a failure to confine or control it. The
results of these latter evaluations will define the relative safety or
risk of a proposed introduction.
The frameworks for microorganisms and plants differ in nomen-
cIature and in emphasis on particular issues, mainly because of dif-
ferences in life cycles, mechanisms of gene transfer, dispersal and
containment or control procedures, persistence, and environmental
factors. Fewer proposed field tests of microorganisms than plants
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may meet the familiarity criterion because the data base, from a
history of planned introductions, is more limited at this time. Means
to confine plants are well established and can be relatively simple,
whereas means to control ~rucroorgan~sms appear to be more difficult.
As a consequence, the subcommittee on microbiology suggests in its
framework a close link between considerations of control and possible
effects. The plant subcommittee's framework shows a distinct sepa-
ration between considerations of confinement and of environmental
effects.
We believe that our evaluation of the scientific issues and our pros
posed frameworks provide the responsible government agencies with
the foundation for a flexible, scientifically based, decision-making
process. Use of the frameworks for evaluation of field tests peanuts
the classification of an introduced organism into a risk category.
Representative terms from entire chapter:
genetic modification
