Risk Assessment and Risk Management

Chapter 8 Scientific Issues: Risk Assessment and Risk Management Photo credit: Grant Heilman, Inc. Contents Page INTRODUCTION . ... ........225 RISK ASSESSMENT . ... .....225 Concerns and Postulated Environmental Risks of Biotechnology . 225 Major Risk Assessment Reports . 227 Biotechnology Ecological Risk Assessment . 231 Applicability of Diverse Bodies of Knowledge to Assessments of Large-Scale Commercial Release . 235 Commercial Release Issues . 240 RISK MANAGEMENT . ... .....247 Design of Science-Based Regulation . 247 Generic v. Case-by-Case Approach . ...247 Relative Risks Compared to Traditional Practices . 248 Cost-Benefit Analyses . 248 Small-Scale v. Large-Scale Issues . 248 SCIENTIFIC METHODS OF MANAGING RISK . .. ..........249 Promoters Turned On or Off by Specific Stimuli . 249 Suicide Genes . .249 . Prevention of Gene Transfer . 250 Combinations of Genes . ... ......250 AGRONOMIC METHODS OF MANAGING RISK . ... .......250 Physical Barriers . 250 Spatial Barriers . 251 Temporal Barriers . 251 SUMMARY POINTS . ... ...251 CHAPTER PREFERENCES . 252 Boxes Box Page 8-A. Ecological Risk Assessment Questions . 233 8-B. Learning by Doing: Successive Field Releases . 238 8-C. Monitoring Microorganisms . 245 8-D. Relevant Research Fields . 246 Figures Figure Page 8-1. Alternative Risk Analysis Approaches . 229 8-2. Risk Assessment Framework for Environmental Introductions . 232 Table Table Page 8-1. Comparison of Traditional and Developing Biotechnology . 248 Chapter 8 Scientific Issues: Risk Assessment and Risk Management INTRODUCTION that such organisms will persist in the environment”? What is the likelihood that they will spread, constituting an The large-scale commercial use of agricultural bio- invasion into the ecological community’? Will they be- technology gives rise to several questions. Does the re- come pests, with a deleterious effect on other species’? lease of large numbers of genetically engineered organisms Will the expression of the gene itself lead to an unwanted into the environment pose special risks’? If so, what is effect on the ecosystem’? the order of magnitude of these risks compared to the risks of traditional agricultural practices’? What benefits Other questions have to do with the recombinant gene offset such risks? itself (38): What avenues exist for gene transfer within and between various species in nature’? How probable Generally, concerns about genetic engineering focus on: are such exchanges and at what rates would they occur. possible ‘‘escape” of a genetically engineered or- if at all? If introduced genes are transferred to genomes ganism, such that it invades new ecological niches existing in nature. how well— and how stably—will the or outcompetes naturally occurring organisms and functions for which they code be expressed? becomes a pest; possible disruption of a delicately balanced ecosystem; Finally, broader, more fundamental questions can be possible direct risks to humans or wildlife; posed: Are we in fact dealing with a phenomenon so possible problems of gene stability and of gene transfer novel that we have no way of predicting outcomes, of to unintended recipient organisms; Performing adequate risk assessment? Do we have a moral possible impact on evolution; and right to manipulate still further the species and the ecol- the sheer “newness” of the technique. ogy of our planet’? Are we losing an intangible, aesthetic quality to our lives by so doing’? Can we at-ford to say This chapter addresses these concerns and describes no to the benefits that this technology can confer on the range of scientific views on biotechnology and risk. agriculture A consensus has developed that risk assessment is de- sirable and feasible. Risk assessment in general is founded Concerns About Plants on principles and methodologies that can apply to biotechnology. We know what questions to ask in assessing Specific concerns relating to genetically engineered ecological risks of planned introductions. A knowledge plants include the possibility that transgenic plants will base already exists pertinent to these questions and risk persist and become serious agricultural weeds; that the assessment studies on this topic are proliferating. Sci- transgenic plants will invade natural habitats and disrupt ence-based risk management builds on this technical local ecological interactions; and that the pollen of trans- knowledge and on our capabilities for risk assessment. genic plants will act as a vector. bringing the introduced genes to other species that may then themselves become Risk assessment methodologies and our technical problem weeds. The likelihood of such possibilities oc- knowledge base make it possible to conduct effective curring remains somewhat controversial, underscoring risk assessments of specific introductions and to manage the importance of information from field trials and re- risks of acceptable introductions. Science-based regula- search. It is noteworthy, however, that transfer of genes tions are central to effective management of risk. A va- from conventionally bred crop plants to noncrop plants riety of scientific and agricultural methods can be used has not created obvious problems in the past, and that to manage risk in particular situations. traditional crop plants rarely have invaded natural ecosystems ( I 4). RISK ASSESSMENT lnvasions of plants (by seeds. fruits. or vegetatively Concerns and Postulated Environmental reproducing units ) involves dispersal, persistence. and Risks of Biotechnology establishment: all three stages must be ‘‘successful if’ engineered plants are to become weeds. For transgenes General Concerns (introduced genes) to move from crop plants and cause Questions arise concerning the impact of introduced or contribute to a weed problem, hybridization with a genetically engineered organisms: What is the likelihood reproductively compatible species must occur. For tiny given crop species, only a small number of the wild To assess risk of problematic infection of humans by relative species that are reproductively compatible are genetically engineered organisms. information must be actually likely to present serious weed problems; how- available on exposure level. This hinges on such factors ever, it is theoretically possible for a plant to become a as bioavailability or likelihood of absorption into cells weed in a novel environment (43). or tissues, specificity, and level of interaction possible of the microorganisms or their chemical products with One specific concern posed frequently by some en- nontarget (human) tissues; and potential of the micro- vironmentalists, among others (32), is that genes for her- organisms for colonization or infectivity. The degree of bicide tolerance might be transferred from crop plants to pathogenicity must be considered as well. Some relevant weeds. If this were to occur, natural selection could favor factors include virulence. Possession of toxins, host range, the trait in weedy neighbors of crops treated with the and relative susceptibility. Generally. risk assessment herbicide. With any use of herbicides, furthermore, in- will factor in predictability of the behavior of the recom- creased selection pressure is put on wild species for any binant DNA identified microorganisms based on their herbicide tolerance traits they might already possess. Such parent organisms, as well as knowledge of specific re- developments might lead eventually to increased use of combinant techniques used (40). chemical herbicides. A fundamental debate has arisen between industry scientists who maintain that crops can Scientists’ concerns focus less on pathogenicity and be genetically engineered to be tolerant of particularly more on the possible impacts of genctically engineered ‘‘environmentally friendly’ herbicides and some envi- microorganisms on the environment. Suggested impacts ronmentalists who say. essentially, that no new tech- include possible influences on: indigenous population size. nology should be used to favor continued use of chemicals diversity of species. the ecological community. natural in the environment. cycles, and evolution of the introduced organisms (76). Microbial environments are complex. By one estimate Concerns About Microorganisms some 109 microorganisms, representing a variety of tax- onomic groups, inhabit one gram of- soil. Uncetanties In part because they are invisible and relatively “un- exist as to possible consequences of sudden introductions knowable, ” microorganisms tend to elicit more concerns on balanced microbial ecosystems (46). Microbial di- on the part of the public than do plants. Parameters of versity in the soil is high (88). This limits the niches concern related to genetically engineered microorganisms available to introduced mirorganisms (86). While in- include the possibility of gene transfer and recombination. troduced microorganisms may thus compete poorly. they the possibility of movement into new environments, and may persist in low-density populations. A key issue is the possibility of infection of nontarget organisms. Ques- whether or nor an unexpected later resurgent bloom or tions asked include: Will genetically engineered microor- population expansion from a low-density population can ganisms give rise to biological risks for humans or other be reasonably envisioned (84). species? Will they give rise to environmental problems’? Do we have the technical understanding to evaluate and Since microorganisms can and do change location. predict any such problems’? questions of dispersal—and

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