Animal Biotechnology Science-Based Concerns (2002) / Chapter Skim
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5. Environmental Concerns
5. Environmental Concerns
Pages 73-92
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From page 73... ...
However, the charge to this committee was not to examine the benefits of biotechnology, or of the technical alternatives, but rather to "develop a consensus listing of risk issues in the food safety, animal safety, and environmental safety areas for various animal biotechnology product categories." The committee also was asked "to provide criteria for selection of those risk issues considered most important that need to be addressed or managed for the various product 73 ~ .
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From page 74... ...
., GENERAL PRINCIPLES OF RISK ANALYSIS Consideration of environmental concerns posed by GE animals must be based on an understanding of key concepts underlying the science and practice of ecologic risk assessment. A seminal review of risk assessment methodology (NRC, 1983)
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From page 75... ...
Because all potential harms might not be known or cannot be known (see Chapter 7) , it will be necessary to update this procedure continually as knowledge accumulates, using an adaptive management approach (NRC, 1996; Kapuscinski, 20023.
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From page 76... ...
, ~ Defining What Exposure Means for a GE Organism and the Likelihood of Exposure: P(E) Exposure is a threshold phenomenon because an initial escape or release of a GE organism might not have a measurable effect on the receiving community; the organism might not be able to establish itself in the community, and might be lost rapidly due to natural selection.
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From page 77... ...
The model is based on the assumption that natural selection acting through these components will determine the ultimate fate of the transgene. The last component, mating success, often is overlooked because it generally is not a factor in artificial breeding programs; it often is, however, the strongest factor driving natural selection (Hoekstra et al, 20019.
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From page 78... ...
provide a retrospective method based on measurement of net fitness components. From a prospective view, the key factor affecting fitness is transgene functionality within the GE organism.
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From page 79... ...
However, environmental concerns posed by animals expressing these types of transgenes cannot be dismissed. First, it is possible for GE organisms to overcome viability disadvantages if other fitness components are enhanced, such as mating success, fecundity, or age at sexual maturity (Muir and Howard, 2002b)
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From page 80... ...
Hence, the concern for this mode of transgene establishment in natural populations is moderate to low based on currently available evidence. However, it is theoretically possible for organisms engineered for production traits to become established in communities as a result of adaptive peak shifts; any such establishment would pose a high level of concern.
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From page 81... ...
Because establishment is the objective and is critical for biocontrol using these techniques, this category of genetic engineering raises the highest probability for establishment. Ability to Escape, Disperse, and Become Feral Another aspect of evaluating the probability of establishment of a GE animal in a community is the organism's ability to escape, disperse, and become feral in diverse ecologic communities.
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From page 82... ...
Highly domesticated species such as poultry or dairy cattle are not well adapted to natural conditions and might not be able to survive and reproduce in a natural setting. However, if wild or feral populations exist locally, the escaped transgenic organisms could breed with those and spread the transgene into populations that otherwise are well adapted to the local environment.
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From page 83... ...
Colonization by GE animals might result in local displacement of a conspecif~c population, which could have a disruptive effect on other species in a community, for example, by releasing competing species from resource competition or prey species from predation (Kapuscinski and Hallerman, 1990~; additionally, the survival of predatory species that depend on the eliminated species could be threatened. This concern is best exemplified by the classic experiment of Paine (1966)
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From page 84... ...
They showed that rainbow trout transgenic for growth hormone were both larger at sexual maturity and lower in viability than their wild-type siblings. Although the mating success of transgenic males relative to g
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From page 85... ...
Escape of domesticated animals, whether or not transgenic, into wild or feral populations also might affect wild-type populations adversely by introducing alleles or allele combinations that are poorly adapted to natural environments (Hinder et al., 1991; Lynch and O'Hely, 2001; Utter, 2002~. If the wild population is sufficiently large, these alleles eventually should be eliminated by natural selection, although it might take many generations to reach selective equilibrium.
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From page 86... ...
. A transgene that increases the fitness of a highly mobile species that becomes feral easily raises the greatest level of concern, (e.g., a transgene conferring salt tolerance on catfish or the phytase gene in mice)
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From page 87... ...
Such functions include, for example, increased nutrient utilization, or new metabolic pathways allowing nutrient synthesis ability, viral or bacterial resistance in any species, and heat or cold tolerance. Few GE terrestrial vertebrates have been produced that fit this category; the best examples to date are the phytase mouse and pig (Golovan et al., 2001a,b)
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From page 88... ...
If a genetically engineered arthropod is to be released within a practical pest management program, any potential ecologic risks associated with its release into the environment must be assessed, although guidelines for conducting such an assessment do not yet exist (Hoy, 1992a; 1992b; 1995~. Anticipation of ecologic risks will depend upon predictions of the impact of changed abundance or dynamics of the engineered species upon resources or species with which the organism interacts in the environment, including predators, prey, competitors, and hosts.
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From page 89... ...
Possible human health effects posed by genetic engineering of disease vector insects are discussed in Chapter 3. In the context of environmental concerns posed by GE arthropods, it is clear that purposeful release of transgenic arthropods will depend upon prior risk assessment and risk management.
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From page 90... ...
Several studies that have focused on Atlantic salmon (Salmo salary expressing a growth hormone (GH) gene construct suggest that transgenesis might affect fitness, but do not provide net fitness estimations needed for parameterizing fitness models predicting outcomes should such fish enter natural systems.
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From page 91... ...
. While indicative that risk issues must be regarded with seriousness, the growing collection of empirical risk assessment studies of transgenic salmonids does not yet provide a body of data useful for parameterizing a model useful for predicting the likelihood that transgenes would become permanently introgressed into wild or feral salmon populations.
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From page 92... ...
Greater knowledge in these areas would support an informed judgment of whether and how to go forward with approval for marketing particular genetically engineered animals. For example, results of well-designed, interdisciplinary studies could prove useful for parameterizing net fitness-based models used for predicting whether transgenic genotypes would persist in natural populations.
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