Environmental Effects of Transgenic Plants The Scope and Adequacy of Regulation (2002) / Chapter Skim
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2 Scientific Assumptions and Premises Underpinning the Regulation and Oversight of Environmental Risks of Transgenic Plants
2 Scientific Assumptions and Premises Underpinning the Regulation and Oversight of Environmental Risks of Transgenic Plants
Pages 52-100
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From page 52... ...
The committee finds, however, that specific types of transgenic and conventional crops can pose unique environmental hazards. Also, the committee finds that there are good arguments for regulating all transgenic crops.
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From page 53... ...
This chapter addresses risk from both perspectives. The 1983 report's approach is followed in using science to illuminate technical understanding of the environmental risks of transgenic crops.
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From page 54... ...
Hazard identification is one of the most subjective and potentially contentious elements of risk analysis. While this report is limited to a consideration of environmental risks, there is some ambiguity in deciding what is and is not an environmental hazard.
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From page 55... ...
For example, one can reduce his or her risk of an accident on a slippery road by slowing down or simply by staying home during inclement weather. Similarly, planting and harvesting transgenic crops in certain ways can reduce the risks associated with them.
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From page 56... ...
Within this class of risk problems, there are circumstances where decision making consists of selecting from among several well-defined options, such as whether to allow the commercialization of a particular transgenic crop. In these situations, risk analysis often consists of anticipating unwanted outcomes associated with each option and measuring their probability should that option be taken.
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From page 57... ...
It is, in part, the flexibility to adjust assumptions and parameters that makes risk analysis particularly useful in a decision support role. This flexibility allows the decision maker to explore the full range of possibilities before coming to a decision.
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From page 58... ...
If risk analysis is expected to play any significant role in establishing the public's confidence in genetically modified crops, it becomes crucial to examine the procedures and methods for conducting a risk analysis with two ends in mind. Finding 2.1: Risk analysis of transgenic crops must fulfill two distinct roles: (1)
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From page 59... ...
Many have noted that risks may not be simply "accepted," so the third stage is then relabeled as "risk management." Because risk analysis of transgenic organisms is itself contentious, the committee chose to adopt the terminology hazard identification, risk assessment, and risk management when discussing risk in its decision support role. Broadly conceived, the techniques of risk assessment are of five general kinds: 1.
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From page 60... ...
The scientific rationale for this method is that regulatory personnel have ready access to confidential business information and understand both current scientific knowledge and the process of risk analysis, so their judgments can be rendered with minimal delays and sufficient scientific accuracy. This is the method used by USDA-APHIS-BBEP to evaluate most of the complex, difficult-to-measure potential risks associated with transgenic plants.
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From page 61... ...
For example, hazard identification is no longer an exercise in listing potential hazards but becomes a deliberative process from which potential hazards are characterized. Moreover, even when science and engineering methods are used to measure the probability that these potential hazards will materialize into bona fide risks, the risk problem is substantially sharpened and redefined by deliberative processes, so it seems appropriate to include this part of risk analysis under the heading of risk characterization as well.
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From page 62... ...
Hence all these processes are better thought of as integrating subcomponents of risk characterization rather than steps in a risk analysis process. Risk Analysis as Decision Support in the Regulation of Transgenic Plants Since the use of transgenic crop plants was first discussed, there has been confusion over the basis for distinguishing between the potential environmental risks associated with these plants and the risks associated with conventionally produced plants.
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From page 63... ...
Below the committee reviews the kinds of hazards that can be associated with transgenic crop plants. None of these kinds of hazards is unique to transgenic plants, and hence no new kinds of hazards are identified.
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From page 64... ...
Finding 2.7: Risk analysis of transgenic crops has played and is likely to continue to play an important role in maintaining the legitimacy of regulatory decision making concerning environmental and food safety in the United States. The Precautionary Principle The Precautionary Principle has been used in multilateral, international agreements to help legitimize a regulatory process based on scientific risk analysis.
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From page 65... ...
As clearly stated in the biosafety protocol and the modified Directive 90/220, science will continue to be the basis of risk assessment. SCIENTIFIC ASSUMPTIONS UNDERPINNING REGULATION OF TRANSGENIC CROPS The Categories of Hazards The initial step in risk analysis and one of the most critical for framing the entire analysis is hazard identification.
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From page 66... ...
or (2) dispersal of seeds directly from the transgenic crops into the surrounding environment.
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From page 67... ...
Specific hazards associated with horizontal transfer are rarely posed, and its significance is largely discussed as a source of unanticipated effects. Presently there are no data to suggest that the extremely low rate of natural horizontal transfer should change for transgenic organisms.
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From page 68... ...
to the contamination of California's wild walnut populations with genes from the cultivated species (Skinner and Pavlik 1994~. There is no reason to imagine that this hazard should be any different for transgenic crops.
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From page 69... ...
evolve to a wildtype phenotype very quickly and could become viable wild populations by the F2 generation. The existence of these populations demonstrates that transgenes that confer adaptation to significant limiting factors can create significant whole-plant hazards, particularly if the ecological effects of transgenic crops are evaluated on global basis.
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From page 70... ...
Transgenic pesticidal crops present a challenge because in some respects they are similar to chemical pesticides that are routinely regulated and in other respects they are similar to conventional breeding and other agricultural technologies that are not regulated at all. Scientific progress has been an awkward accommodation between these perspectives that has yet to reach scientific consensus.
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From page 71... ...
Most transgenic crops have effects on non-target pests. Although these effects are expected to sometimes be positive and sometimes negative, studies documenting only reductions in non-target pest populations have been published.
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From page 76... ...
Virus-resistant transgenic crops have not been used extensively, but many viruses have evolved resistance to conventional virusresistant crops (Fraser 1990~. Fungal and bacterial resistance is not yet commercially available in transgenic crops, but both groups of organisms have evolved resistance to conventional crop resistance, sometimes within five years (Delp 1988~.
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From page 77... ...
Environmental Risks of Transgenic Crops and Conventionally Bred Crops Despite nearly 20 years of scientific discussion, scientific debate continues about whether the risks associated with transgenic crops are similar to or different from those associated with conventional crops. The source of scientific disagreement is that in some ways transgenic crops are just like conventionally bred crops, but in other ways they are quite unlike conventionally bred crops.
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From page 78... ...
The unresolved scientific challenge is to determine if the range of genetically engineered crop varieties has a similar degree of environmental risk as the range of conventionally produced crop varieties. Theoretically, the most quantitatively robust estimate of environmental risk for transgenic crops would compare the probability of environmental damage associated with transgenic crops to the probability of environmental damage for all crops.
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From page 79... ...
Transgenic organisms have potential environmental risks, but the committee expects that most of them will not produce significant actual environmental risks. Consequently, the committee also suggests that for environmental risk regulatory oversight should be designed to winnow the potentially riskier transgenic crops from the less risky ones before a substantial regulatory burden is imposed on the less risky ones.
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From page 80... ...
Before discussing the scientific details of the issue related to transgenic crops, the committee addresses two related issues. First the Office of Science and Technology Policy (OSTP)
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From page 81... ...
Federal Plant Pest Act and APHIS Regulation Invasiveness, which is the alteration of community or ecosystem structure or function, is the main environmental risk of nonindigenous species. Invasiveness is a function of both the organism phenotype and
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From page 82... ...
Finding 2.9: A logical scientific argument can be made without reference to conventional crops that all transgenic crops should enter into regulatory oversight. ~ ~Nonindigenous~ ' Species Invasive Species FIGURE 2.1 Venn diagram illustrating that invasive species are a small subset of all possible nonindigenous species.
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From page 83... ...
Moreover, because this assessment should be done on a case-by-case basis, all transgenic crops should be reviewed through regulatory oversight. Again, most genetic changes would be expected to have low environmental risk, so all transgenic crops should be reviewed quickly to identify the smaller fraction that will need closer scrutiny.
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From page 84... ...
~ ~ Crop Plants Transgenic Crop Plants with Environmental Risks FIGURE 2.2 A Set of all conventional crop plants and those with unacceptable environmental risk (assumed to be none)
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From page 85... ...
//AII Conventional\ ' Crop Plants \ Conventional Crop Plants with Environmental Risks B /'AII Transgenic-\ Crop Plants Transgenic Crop Plants with Environmental Risks FIGURE 2.3 A
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From page 86... ...
Justification If we accept the fact that some conventionally bred crops can have significant risks, we cannot automatically conclude that a transgenic crop with a similar trait needs no regulation. For example, just because a sulfonyl urea-tolerant conventionally bred canola exists does not mean that the potential environmental effects of engineered canola with this trait should not be carefully reviewed.
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From page 87... ...
In a broader context, transgenic crops could be compared to alternative technologies or technological systems for reaching similar production and environmental goals. For example, the risk characterization might evaluate the policy issue of which technologies or technological systems have lower environmental risks and should be encouraged for future development.
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From page 88... ...
The first is that for the evaluation of risks of transgenic crops several reference scenarios can be found, which imply that risk comparisons to conventional breeding are sometime irrelevant, as illustrated by some of the examples described above. Thus, general statements about the relative risk of particular transgenic crops to their conventional counterparts will not be the only basis for risk characterization.
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From page 89... ...
Conventional plant breeding is not always an appropriate reference comparison and for the cases presented here, it was not used as an appropriate reference. Second, there are unique risks associated with certain transgenic crops.
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From page 90... ...
The final step is to pick up any residual effects stemming from any interactions between the trait and the untransformed organism that require additional assessment. The two-part model makes a procedural commitment to making the untransformed crop plant the central reference scenario for contextualizing the risks of a transgenic crop.
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From page 91... ...
A whole-organism model would initially focus on identifying the potential hazards associated with the transgenic crop variety. The appropriate reference scenario for hazard identification may include the untransformed crop and conventionally produced crops with comparable
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From page 92... ...
The theoretical rationale supporting the whole-organism model is that the risks and hazards associated with a transgenic crop plant occur as a result of the trait in the crop plant in a particular environment. The risks and hazards do not occur from the trait separated from the crop plant separated from the environment.
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From page 93... ...
It is a weakness because unknown or unanticipated hazards cannot be evaluated simply because they have not been identified. Because the hazards associated with complex systems cannot all be unambiguously identified ex ante, this is its most serious weakness.
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From page 94... ...
. An "or" gate signifies that if any of the input statements are true, the output statement is true and therefore the inverse of the product of the inverse of the input probabilities can be used to compute the output probability, assuming the input statements are independent.
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From page 95... ...
This tradition is well developed in the aeronautics industry, where airplane safety and safety systems are subjected to rigorous fault-tree analyses (Lloyd and Tye 1982~. A simplified fault-tree model for the safety system associated with APHIS regulation of transgenic crop plants is illustrated in Figure 2.5.
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From page 96... ...
For example, an event chain analysis of the potential non-target risks associated with a transgenic crop producing a toxin could begin quite generally, because we know the toxin that would cause any of the nontarget risks that could occur (see Figure 2.6~. Consequently, an event-tree analysis of non-target effects can be initiated through a toxin fate and transport analysis, tracking where and when a toxin goes until it is degraded into nontoxic forms.
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From page 97... ...
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From page 98... ...
Event-tree analysis may become particularly useful when risks associated with transgenic crops with many traits are characterized. Finding 2.15: The two-part model may bias a risk assessment either toward a finding of no significant risk or a finding of significant risk.
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From page 99... ...
It explains that risk analysis typically must fill two roles: providing technical information to decision makers, and creating confidence among stakeholders in the risk analysis process. The specific importance of the second role in the risk analysis of transgenic plants is discussed.
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From page 100... ...
This chapter ends by pointing out that there are a number of general approaches for formally examining a risk analysis to determine where errors could occur. These formal examinations could be helpful in assuring the rigor of the current system used for transgenic plants.
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