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Genetically Modified Crops and Foods (I-00) Full Text
| Background and Introduction The Technology The Promise of Food Biotechnology Producing a Transgenic Plant Transgenic Technology in Agriculture Currently Marketed Transgenic Crops | Safety & Consumer Issues Human Health The Environment Consumer-related Issues, Consumer Choice, and Food Quality |
| Regulation Regulation of Transgenic Crops in the United States | Conclusions Summary and Comment References |
NOTE: This report was presented as CSA Report 10 at the 2000 AMA Interim Meeting; it represents the medical/scientific literature on this subject as of December 2000.
Largely because of increased efforts by activists that have aroused consumer concern about genetically modified (GM) foods and the possibility of international trade disputes, several scientific and governmental bodies have issued reports on selected aspects of GM crops and foods in the last 2 years.1-11 This report considers their findings and conclusions in explaining the processes for introducing transgenes into plants and the regulation of transgenic crops and GM foods in the United States, and in discussing potential risks and benefits of these with respect to human health and the environment. Key issues related to consumer choice, food labeling, and global food production are also examined, forming the basis for the report's conclusions and recommendations.
Introduction
Crops that have been genetically modified to resist pests and tolerate certain herbicides through the use of recombinant DNA technology have been marketed in the United States since 1995. Such crops are intended to produce higher yields and reduce environmental exposure to commonly used pesticides and herbicides. Many products derived from corn and soybeans, in particular, have been on the shelves of United States grocery stores during this period, without any apparent unintended or ill effects. Earlier in the decade, GM tomatoes with altered ripening properties were introduced.
However, fueled by general food safety fears in the United Kingdom due to the mishandling of the bovine spongiform encephalopathy crisis and intensive negative press coverage of GM foods, genetically engineered crops have prompted serious opposition in Europe.12-14 Dioxin-contaminated animal feed in Belgium, HIV-infected blood in France, and the high degree of politicization of regulatory decision-making in Europe have further eroded public confidence in government. A significant proportion of the European public is not convinced that foods derived from GM crops are safe to eat, nor do they believe that the crops themselves are environmentally safe. Activist groups and a smaller percentage of consumers in the United States are now expressing similar concerns. These concerns about GM foods contrast with the widespread acceptance and use of many recombinant products in health care (eg, human insulin and growth hormone, erythropoietin, hepatitis B vaccine, tissue plasminogen activator, interferons, factor VIII, antihemophiliac factor, etc).15
Nevertheless, in June 1999, environmental ministries from the European Union instituted a de facto moratorium on GM crops by failing to move on new dossiers for new varieties of GM foods until new regulations are in place.16 In the United States, a few American companies announced at least a temporary removal of GM ingredients in their products, as did some breweries in Japan and tortilla makers in Mexico. If such actions intensify, US farmers may have to reevaluate decisions to plant GM crops. Although, the total number of acres of GM crops planted globally in 2000 continued to increase, the rate of increase has slowed.17 The acreage devoted to GM corn decreased in the year 2000, largely because problems caused by the European corn borer have recently diminished. Arguments about the safety of GM crops have obscured the deeper ramifications of their potential use in poor countries of the world, where agriculture is the predominant economic activity and food supply a top political and economic priority. Back to Top
Literature searches were conducted in the MEDLINE database and Lexis/Nexis GenMed library for articles between 1990 and September 2000 using the terms genetic engineering combined with food microbiology; food technology; agriculture; plants, edible; food; and crops, agricultural. A secondary search was conducted for articles between 1995 and September 2000 using the search term plants, transgenic. References containing information relevant to the safety, regulation, and environmental impact of transgenic crops and foods were examined further. Additional references were culled from the bibliographies of these pertinent references. The World Wide Web was searched for information using the search terms genetically modified foods or genetically modified crops, revealing several links to additional scientific and regulatory sites. Back To Top
The Promise of Food Biotechnology
The potential for transgenic technology in agriculture is well recognized.18 Currently, transgenic plants are being created that are resistant to pathogens and pesticides, have improved nutritional quality and delayed ripening, and improved flavor.19 Transgenic plants resistant to a specific pest have increased yields and benefit the environment by reducing the use of conventional pesticides. Pest-resistant cotton crops reduced pesticide use in the United States by 1 million kilograms between 1998 and 1999.20 Other potential benefits include tolerance to biotic and abiotic stresses and the ability to cultivate marginalized lands.
GM foods with improved preservation and processing qualities are already available. Other GM foods hold the promise of improving nutrition and preventing and curing disease.21 None of these products are yet commercially available but include plants with a better source of nutrients (rice with provitamin A)22; genetic engineering of plant lipids23; plant-based production of xenogenic proteins24; vaccines25; antibodies26,27; industrial enzymes and proteins.28 Plant-derived antigenic proteins have delayed or prevented the onset of disease in animals. Back To Top
Humans have been modifying crop plants for centuries by plant breeding. Plant breeders have used selective breeding to create hybrid offspring, via the exchange of genetic material, to increase yields, develop disease resistance, and enhance agronomic qualities.1,2,6,9,11 The late 20th Century version of this is the production of transgenic plants. Traditional breeding techniques are limited to genetic mating between related species, and require several generations (often years) to achieve the desired results. With transgenic technology, a genetic trait can be introduced into a selected plant via the direct introduction of the gene responsible for that trait, a process not constrained by genetic similarity and one that broadens the number of potential sources from which desirable genetic traits can be obtained.2,29-31
Introduction of Transgenes. There are two ways to insert and express transgenes in plants (plant transformation). The in vitro methods include technologies such as microinjection of the DNA, direct DNA uptake into protoplasts with or without application of an electric stimulus (electroporation), and microprojectile (or "particle") bombardment.30 Vector-based technologies include the use of viral vectors to transiently introduce the DNA into the plant and the use of Agrobacterium tumefaciens T-DNA-mediated transformation for stable transformation of the plant.30 Plants are especially suitable for genetic manipulation because many of them self-fertilize and produce large numbers of progeny. This facilitates detection of the recombinant plant with the desirable trait or the recombinant genotype. Plants can also be easily regenerated not only from seed but from residual plant parts such as stems and leaves. Whole plants can also be regenerated from single cells or protoplasts.
In vitro Techniques. Microinjection involves the direct injection of the transgene into protoplasts using a fine needle and microscopic manipulation, a process that is technically difficult and labor intensive.30 Direct DNA uptake involves comingling protoplasts and the DNA of interest in a facilitating medium such as polyethylene glycol (PEG), which allows direct uptake of the DNA by the protoplast. This procedure can be enhanced by electroporation, which temporarily disrupts cell membrane integrity.30 Direct DNA uptake has been largely superceded by particle bombardment.30,32 In this technique, gold or tungsten microparticles are coated with the DNA of interest and are propelled directly into plant cells or tissues via a "gene gun" using electrical discharge or compressed helium gas. If the target tissue regenerates, whole transgenic plants can be produced. This procedure is now the most commonly used in vitro technique.
Vector-based Techniques. Transformation can be accomplished with recombinant viral vectors bioengineered from plant viruses such as the cauliflower mosaic virus.9,30 Viral vectors can be fragments of viral DNA containing the DNA to be transferred or the viral particle itself. Replication of the viral particle is prevented by manipulation of the viral DNA, so that the end product is a nonpathogenic viral vector carrying the transgene of interest. Viral-based transformation is generally transient, not stable.
A. tumefaciens is a bacterium that has been called "nature's own genetic engineer"9 because it naturally transfers its own DNA into the plant it infects.33-35 Attenuated strains of this bacterium have been created that can be modified to carry the transgene of interest but will not induce the tumors typically associated with wild type infection with A. tumefaciens. The new transgene is incorporated into the plant DNA through the A. tumefaciens border sequences, which facilitates its transfer and stable integration, and in most cases does not transfer unwanted bacterial DNA. Because of the technique's simplicity, vectors capable of infecting and transforming plants other than the broad-leaved plants that are the natural hosts for A. tumefaciens have been developed.34,35
There are both advantages and disadvantages to these two methods of plant transformation. The in vitro protocols tend to create transgenic plants containing a high copy number of the transgene, many of which are either rearranged or catenated. These forms of the transgene may actually be detrimental if they result in homology-dependent suppression where complete (and useful) copies of the transgene become silenced (not expressed) via homologous recombination with these rearranged or catenated copies.9,30 Electroporation and microinjection techniques depend on the ability to regenerate the transgenic protoplasts into whole plants, a process that can be difficult for many species and impossible for some. While particle bombardment can be used with most plant species, the technique is fairly inefficient and only a few cells are stably transformed with the transgene. A. tumefaciens-mediated transformation is fairly efficient for several plant species and results in a low copy number of intact, non-rearranged transgenes integrated into the plant genome. Unfortunately, transformation of many important crop species, such as many cereal grains and Soya bean, is inefficient.30 However, new technologies are being developed that are overcoming the current limitations of A. tumefaciens-mediated transformation.34,35
Currently, scientists are exploring techniques that would combine the best attributes of A. tumefaciens-mediated transformation (high efficiency, low copy number, and intact transgenes) with that of particle bombardment (species-independent transformation). Recently, maize has been efficiently transformed via a protocol where the transgene flanked by the T-DNA border sequences of A. tumefaciens is bombarded into maize cells with two other plasmids expressing the genes from A. tumefaciens responsible for the integration of the T-DNA borders into the host genome.35 This process resulted in efficient integration of the transgene at low copy numbers.
All plant transformations still are limited because the transgene cannot be directed to a specific location on the plant genome.30,36 The integration process is more or less random. Because the efficiency with which an integrated transgene is expressed is influenced by its location within the host genome following the transformation, many individual transgenic plants must be grown to ensure that an individual with the desired characteristics can be detected and selected.36 For example, integration of the transgenes into host chromosomal locations where the DNA is highly methylated can also result in silencing of the transgene should it become highly methylated as a result of its integration.9,37
Progress is being made on techniques to allow site-specific recombination to deliver the transgene to a specific chromosomal location.38,39 Interestingly, these methods have not yielded more consistent expression of the transgene, indicating that location alone is not enough to determine expression.30 Other mechanisms, such as cosuppression and post-transcriptional silencing, are now being discovered that may also result in silencing of the transgene.40,41 Recent research efforts to create transgenic plants with a more consistent expression of the transgene include techniques where the transgene is flanked by "attachment sequences."42 These sequences effectively reduce the variability of the transgene expression to that caused by environmental effects; that is, the degree of variability of transgene expression is the same as that seen in genetically identical plants.43 This new technology promises to eliminate location effects and may reduce the number of plants that will have to be grown and screened in order to select an appropriate transgenic plant for expansion and breeding.
Selection. A method is needed to distinguish and then select the cells and plants that have successfully taken up the transgene and are adequately expressing the desirable trait. To accomplish this, a marker gene is usually co-introduced with the transgene that will allow easier detection of plants that are expressing the transgene. Until recently, many of these markers were genes that conferred resistance to an herbicide or an antibiotic.1,9 Potential transgenic plants/cells can then be sprayed with or grown on media containing the appropriate herbicide or antibiotic. Those that were successfully transformed will survive; non-transformants will die.
Partly because of the recent focus on horizontal gene transfer (see section on Safety of Genetically Modified Foods: Human Health), but primarily because of technical benefits that can be achieved, new marker gene systems have been developed that code for color expression or some other obvious phenotype to enable visual selection.9,44-46 Eventually, there may be little need for marker genes as more efficient expression of the transgene occurs with the development of new techniques. With current efficiency rates reaching as high as 5%, it may soon be possible to screen for possible transformants by directly looking for the trait coded for by the transgene or for the transgene itself.9
Other Current and Future Strategies and Uses. Improved understanding of both plant defense mechanisms and pathogen action will lead to better transgenic strategies for improving the resistance of plants to pathogens.47 More novel plant protection techniques have already been mentioned above and these are expected to reach their potential in the next 10 years. Two new techniques show significant promise in generating the first broad-spectrum fungus-resistant crops: the expression of antifungal proteins48 and hypersensitive-response-based strategies.49 It is clear that the introduction of a single transgene usually will not be sufficient to achieve long-lasting and broad-spectrum disease resistance. In this regard, transgenes imparting insect resistance may be combined with transgenes imparting fungal resistance in a single plant.30 It is anticipated that a balance favorable for both farmers and the environment can be achieved where there is minimal use of herbicides and pesticides through the use of appropriate transgenic technology.
Finally, transgenic plant technology is just beginning to see utilization for expression of proteins beneficial to humans and animals.21,22,24,25 Plants are excellent vectors for vaccine delivery and antibody production. Additionally, as plant disease protection improves, there will be development of transgenic plants with longer shelf lives, better taste, and higher nutritional value. Back To Top
Regulation of Transgenic Crops in the United States
The emergence of recombinant DNA (rDNA) sequencing methods and the availability of plasmid and viral vectors for use in creating genetically engineered organisms in the 1970s and early 1980s led to development of guiding principles on both the technical aspects of recombinant DNA research, and regulatory concerns about the release of genetically engineered organisms into the environment.50-52 In 1986, the Office of Science and Technology Policy (OSTP) published the "Coordinated Framework for the Regulation of Biotechnology," which considered existing regulations and laws applicable to biotechnology and proposed how the United States Environmental Protection Agency (EPA), the United States Department of Agriculture (USDA), and the Food and Drug Administration (FDA) would cooperate in the review of new biotechnology. This framework, which is still in existence today, established the basis for regulation by the USDA, FDA, and EPA of new plant varieties produced by rDNA techniques.53 Determining which agencies have responsibility for a particular plant-related product depends on two factors: (1) the traits that have been engineered into the plant; and (2) the use of the crops that will be harvested. The USDA is responsible for ensuring that new plant varieties are safe to grow; the FDA is responsible for ensuring that new plant varieties are safe to consume for food or feed; and the EPA is responsible for ensuring that new pest-resistant varieties are safe to grow and consume.
United States Department of Agriculture (USDA). The USDA has the responsibility for protecting plants and for safeguarding American agriculture under the Federal Plant Pest Act (FPPA).54 In 1987, the USDA proposed regulations for review of plants genetically modified with rDNA methods, including procedures for obtaining permits for field trials, and in 1992 it issued a regulation (finalized in 1993 and later expanded in 1997) governing an expedited process by which the Animal and Plant Health Inspection Service (APHIS) would deregulate and approve such plants for commercial planting.55-57
Regulations governing field tests (release into the environment) concern so-called "regulated articles." These are organisms, plants, or plant parts that contain any part of a known plant pest. Because plasmids of A. tumefaciens and the regulatory sequence from cauliflower mosaic virus often are used to introduce and drive the expression of genes in genetically engineered plants, the USDA has determined that the majority of plants developed using rDNA technology fall under these regulations. Field tests require a permit from APHIS, which reviews applications and prepares an Environmental Assessment (EA) in which the potential environmental impact of the release is evaluated. If this is deemed not significant, a permit is issued.
Effective April 30, 1993, certain field tests may qualify for the notification process, which expedites the permitting procedure (notifications are a type of release permit). Such field tests must involve tomatoes, corn, tobacco, soybeans, cotton or potatoes, and must meet other specified eligibility criteria.56 The agency does not prepare an EA for these field tests. Additional organisms and gene constructs were included in the 1997 modification.57
After several years of field trials, a developer may petition APHIS to have an "article" removed from the regulatory process. Commercialization requires an EA that addresses safety concerns and obligations of the agency under the National Environmental Policy Act (NEPA). APHIS conducts an EA, and if it concludes the plant carries no significant risk, a determination of nonregulated status is issued, clearing the way for growing the plants without further APHIS oversight. Records and EA of all field tests conducted and petitions for deregulation are contained in a USDA Environmental Releases Database.
Food and Drug Administration (FDA). The Federal Food Drug and Cosmetic Act (FFDCA)58 gives the FDA a broad range of legal authority and regulatory oversight to ensure the safety of whole foods. The FDA's approach to regulation of GM foods is based on a 1992 Statement of Policy, which holds that "safety concerns should be characteristics of the food product, rather than the fact that new methods are used."59 Under this policy, companies were asked to determine whether formal review is required (based on genetic stability, compositional and nutritional quality, toxicity and allergenicity of the gene product) and were required to submit nutritional and safety data if there is reason to believe that new plant varieties may pose risks. A key concept in the initial safety assessment is that of "substantial equivalence" (see section on Safety of Genetically Modified Foods: Human Health). Subsequently, the FDA recommended voluntary consultation if companies were intending to market a product, requesting that firms provide a summary of their food (including animal feed) safety and nutritional assessment to the agency and discuss their results with agency scientists prior to commercial distribution.60 All products currently on the market have gone through this voluntary consultation.
Recently, the FDA announced it will publish a proposed rule mandating that developers of GM foods notify the agency when they intend to market such products. The FDA also will require that specific information be submitted to help "determine whether the foods pose any potential safety, labeling or adulteration issues."61 This proposal will strengthen the process by specifically requiring developers to notify the agency of their intent to market a food from a bioengineered plant at least 120 days before such marketing. Furthermore, supportive documentation submitted by the company and the agency's conclusions will be made available to the public on a Web site. The FDA also announced plans to augment relevant advisory committees by adding scientists with agricultural biotechnology expertise and to issue draft labeling guidance to assist manufacturers who wish to voluntarily label their foods as made with or without the use of bioengineered ingredients.
Environmental Protection Agency (EPA). The EPA's Office of Pesticide Programs--Biopesticides and Pollution Prevention Division regulates substances used for pest control under the jurisdiction of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) and parts of FFDCA. In 1994 (amended in 1997), the EPA issued a proposed a rule to regulate the pesticidal substances in pest-protected plants as "plant pesticides" under FIFRA and FFDCA.62,63 Field tests require an experimental use permit. Registration considers the results of the field tests (including effects on nontarget organisms and environmental degradation rates), product characterization, acute oral toxicity tests, digestibility, and allergenicity screens.
The 1994 proposed rule describes which plant pesticides would be regulated and which would be exempted. Plant pesticides are defined as "a pesticidal substance produced in a living plant and the genetic material necessary for the production of that pesticidal substance, where the substance is intended for use in the living plant." The proposal establishes three categories of plant pesticides that would be exempt from regulation under FIFRA: (1) genetic material that encodes for a pesticidal substance that is derived from plants that are sexually compatible; (2) those that act by affecting attachment or invasion; and (3) coat proteins of plant viruses. Under FFDCA, the proposal would exempt these three categories: (1) as above; (2) genetic material encoding the pesticidal substance that is derived from a food plant; and (3) pesticidal products that do not result in a new or significantly different human exposure.
Thus, the EPA's current proposed rule would exempt or regulate plant pesticides based on the sexual or taxonomic relationship between the organism from which the gene came and the plant into which it is inserted on the novelty of the trait conferred. By relying on sexual incompatibility or novelty as a regulatory trigger, the proposed rule focuses on pest-resistant plants produced using biotechnology and assumes that such traits increase the likelihood of novel exposure or hazards to human health or the environment. Back To Top
Transgenic Technology in Agriculture
The potential for transgenic technology in agriculture is enormous. Currently, transgenic plants are available that are resistant to plant pests and herbicides (see below), or that have improved nutritional quality, delayed ripening, and improved flavor. It is anticipated that plants will soon be used to produce polypeptides for pharmaceutical or technical use. Plant-made vaccines or antibodies are especially attractive because plants do not carry human diseases, thus reducing the requirements for screening for bacterial toxins and viruses. These products are currently in clinical trials after very effective production efforts. Back To Top
Currently Marketed Transgenic Crops
More than 40 transgenic crop varieties have been cleared through the federal review process with one or more features of pest protection (insect and viruses) and tolerance to herbicides (Table 1 [PDF, 87KB, requires Adobe® Reader®]). In addition to these varieties, some crops have been introduced with enhanced agronomic features (tomatoes and cantaloupe with modified fruit ripening properties; canola and soybean with altered oil composition).
Plants Resistant to Insects: Bt Crops. The most widely used transgenic pest-protected plants express insecticidal proteins derived from the bacterium Bacillus thuringiensis (Bt).64 Bt is a gram-positive, spore-forming soil bacterium. Many isolates produce crystalline inclusions on sporulation. These parasporal crystals contain potent insecticidal d -endotoxins classified as crystal toxins (Cry) or cytolytic toxins (Cyt).65 The toxins are synthesized as protoxins. On ingestion by insect larvae, the crystals are solubilized in the alkaline environment of the insect gut where insect proteinases release the active toxin. This toxin binds to specific receptors on the midgut cells of susceptible larvae and results in the formation of pores, causing osmotic lysis of the cell.66-68 Each protein is active in only a relatively small number of insect species. Specificity is to a large extent determined by the toxin-receptor interaction, although solubility of the crystal and protease activation also play a role.69 Members of the Cry gene family are grouped in subfamilies according to their specificity for members of the insect families Lepidoptera (caterpillars, Cry1, Cry2 and Cry9), Diptera (flies and mosquitoes, Cry2 and Cry4), and Coleoptera (beetles, Cry3) (Table 2 [PDF, 87KB]). There is a tendency to consider Bt toxins as all biochemically similar, but the DNA sequence similarity among toxins can be less than 25%, and more than 160 genes have been identified to date.70 Recently, Bt proteins with a wider spectrum of insecticidal properties have been discovered.71 Bt sprays are aerosols of intact B. thuringiensis cells that are used to reduce insect damage to crops grown in the absence of chemical pesticides. They have been in use since the 1950s, but their effectiveness is limited by instability of the crystals in UV light and an inability of spray applications to penetrate tissues and therefore to reach insects in all parts of the plant.
In addition to insect-resistant plants created by the expression of Bt d -endotoxins, plants have been created containing inhibitors directed against diverse proteinase and amylase inhibitors, lectins, oxidases and chitinases.31
Plants Resistant to Viral and Fungal Pests. Initial attempts to create viral resistant plants were based on introducing genes encoding viral coat proteins, viral replicases, viral movement proteins, and defective interfering RNAs and DNAs that would confer pathogen-derived resistance.31,72 Pathogen-derived resistance can occur in a number of ways.73-75 The expression of a normal or altered form of a pathogen protein in transgenic plants can disrupt the pathogen's normal pattern, or the timing of expression of that protein when it attempts to attack the plant. Alternatively, the transgenic expression may interfere with the pathogen's ability to interact with the plant. Pathogen-derived resistance can also trigger mechanisms within the host plant that will intensify the plant's natural protection processes against the pathogen.76
Virus resistance due to the transgenic expression of viral coat proteins is the most predominant form of pathogen-derived resistance.77,78 Crops that have been made resistant in this way are papaya, squash, and potato; viral resistance also has been transferred to potatoes with the replicase enzyme from the potato leaf roll virus (Table 1 [PDF, 87KB]). Using coat proteins, resistance has also been introduced into tomato, watermelon, barley, sweet potato, and other crops under development. Expression of a viral coat protein in plants interferes with the uncoating of the viral genome and delays or prevents the virus from establishing a productive infection.79-83 When multiple viral proteins are expressed, the plant will be resistant to multiple viruses.84
Additionally, new research is investigating ways to inhibit common viral processes by expressing ribosomal inactivating proteins, or double-stranded RNA-specific ribonucleases.31 Ribosomal inactivating proteins affect both eukaryotic and prokaryotic ribosomes and inhibit protein synthesis, and one has been shown to specifically target fungal ribosomes.74 However, some of these proteins also inhibit plant ribosomes and thus are not useful.
Plants with Inducible Resistance Genes. All plants have natural proteins that can inhibit many different types of pathogens, ranging from bacteria to fungi.76 In many cases, this resistance is attributable to a single gene locus in the plant interacting with a matching avirulence gene in the pathogen. The interaction of the products from these two genes creates an incompatible reaction such that the pathogen is unable to infect the plant.76 This incompatibility is often associated with rapid cell death at the site of infection, commonly referred to as a hypersensitivity response, which prevents further infection by the pathogen. By transgenically introducing combinations of different resistance genes and different pathogen avirulence genes, it is possible to engineer natural resistance responses in a wide variety of pathogens and pests. However, constitutive expression of a matching pair will lead to plant death, so it is necessary to control expression of the gene pair by placing them under the control of a pathogen- or chemical-inducible promoter.85,86
Plants Tolerant to Herbicides. Transgenic technology has also been used to introduce transgenes into plants that will enable them to be tolerant of a specific herbicide, usually through the expression of an altered target enzyme that is insensitive to key herbicidal steps (Table 1 [PDF, 87KB]). Already approved for commercial use are transgenic corn, rice, rapeseed (oilseed rape or canola), soybeans, sugar beets and cotton tolerant to at least one of the following herbicides: glufosinate, glyphosate, or bromoxynil. Of these, glyphosate-tolerant plants, especially soybeans, have received the most widespread commercial use. Unlike many herbicides, glyphosate has low toxicity, is safe for humans and animals, and degrades quickly in the soil.11 Thus, it is an environmentally desirable herbicide. However, glyphosate is a broad-spectrum herbicide that cannot be applied to crops that have not been modified to be tolerant to glyphosate, because glyphosate would kill both the crop and the weed. The availability of glyphosate-tolerant crops now allows farmers to use glyphosate to control weeds without affecting the health of the crop.2 Back To Top
Safety of Genetically Modified Foods: Human Health
GM foods have been available for fewer than 10 years. Food products from more than 3000 million acres of GM plant products have been grown globally over the past 6 years. Worldwide, many people are eating GM foods with no overt adverse effects on human health reported in the peer-reviewed scientific literature and according to regulatory agencies.1 Nevertheless, long-term effects are theoretically possible. Currently, safety assessments of GM food involve many kinds of analyses. It is generally agreed that the properties of a GM food should be the focus of risk assessment, not the process by which it was produced.1
Toxicity of Foodstuffs. The general strategy for assessment of GM foods is to: (1) obtain and assess information on the characteristics of the genetic modification, including the function and properties of newly inserted genes; (2) assess the safety and nutritional properties of newly expressed substances in the food; (3) identify and evaluate unexpected changes in the composition of the modified product due to insertion of novel genes or suppression of constituent genes; (4) evaluate the influence of food processing on the toxicological properties of the new food; and (5) evaluate food consumption patterns of the modified product compared with its conventional counterpart.4
One commonly used safety assessment tool is the concept of "substantial equivalence." This is scientifically sound and provides a useful historical baseline for judging safety.4,7,11 Regulations in most countries, including the UK, include some variation of substantial equivalence determinations. This concept was recognized by the Organization for Economic Co-operation and Development (OECD) in 1993, further developed by the Food and Agriculture Organization (FAO)/World Health Organization (WHO) Consultation in 1996, and recently reaffirmed by both, with particular reference to foods produced by modern biotechnology.4
Substantial equivalence involves a thorough analysis to demonstrate that the specific GM food product possesses similar levels and variations in critical nutrients and toxicants as do the parental plant variety and other conventional varieties of that crop. The presence of novel DNA or protein does not preclude a GM food from being considered substantially equivalent to a conventional food in the United States. If a new food or component is considered to be substantially equivalent to an existing food or component, it can then be treated in the same manner with respect to its safety and nutritional assessments. Any defined differences are the subject of additional safety assessments, which may include nutritional, toxicological, and immunological testing as appropriate. It may be necessary in certain instances to undertake feeding studies in animals, but practical difficulties are encountered in evaluating the safety of whole foods in conventional toxicology studies.
Nevertheless, this targeted approach has been questioned with respect to its ability to detect and evaluate the impact of unintended effects, such as the acquisition of new traits or loss of existing traits. As the complexity of GM crops increases, profiling techniques (ie, DNA microassays, mRNA profiling techniques, proteonomic, chemical fingerprinting) may be valuable in increasing the probability of detecting unintended effects.4
Allergenicity. Food allergies affect 1% to 2% of the population.87 Virtually all food allergens are proteins. Genetic engineering is capable of introducing allergens into recipient plants,88 but the overall risks of introducing an allergen into the food supply are believed to be similar to those associated with conventional breeding methods. If a GM food contains the product of a gene from a source with known allergenic effects, the gene product should be assumed to be allergenic unless proven otherwise. There are no known cases of allergic reactions caused by marketed foods derived from GM plants. Of note, genetic engineering also offers the opportunity to decrease or eliminate the protein allergens that occur naturally in specific foods through the use of, among others, antisense technology.1
A decision tree analysis is used to screen proteins from GM foods for possible allergenicity.89 Assessment is normally accomplished by evaluating the source of the gene; the sequence homology of the newly introduced protein to known allergens; the immunochemical reactivity of the newly introduced protein with IgE antibodies from the serum of individuals with known allergies to the source from which the genetic material was obtained (if applicable); and the physicochemical properties of the newly introduced protein (effect of pH and/or digestion; heat or processing stability). Animal models are lacking to assess the allergenic potential of foods and food proteins.
Antibiotic Resistance Markers. Horizontal gene transfer from plants to environmental bacteria or from plant products consumed as food to gut microorganisms or human cells is generally acknowledged as an exceedingly rare possibility, but one that cannot be completely discounted.
The transfer of plant DNA into microbial or mammalian cells under normal circumstances of dietary exposure would require all of the following events to occur:4 (1) the relevant gene(s) in the plant DNA would have to be released (excised), probably as linear fragments; (2) the gene(s) would have to survive nucleases in the plant and gastrointestinal tract; (3) the gene(s) would have to compete for uptake with dietary DNA; (4) the recipient bacteria or mammalian cells would have to be competent for transformation and the gene(s) would have to survive their restriction enzymes; and (5) the gene(s) would have to be inserted into the host DNA by rare repair or recombination events, and the inserted gene would have to be stably maintained.
Numerous experiments have evaluated the possibility of transfer of plant DNA to microbes and mammalian cells. To date, there are no reports that marker genes in plant DNA transfer to these cells. There are reports that bacteriophage and plasmid DNA when fed to mice at very high levels can later be detected in their cells,90 but no data exist to demonstrate that plant DNA can be transferred to and be stably maintained or expressed in mammalian cells.4 There is some experimental data for transfer to bacteria under laboratory conditions,91 but only if homologous recombination can be facilitated.
Transfer of (marker) antimicrobial resistance genes would be of potential clinical and veterinary importance; however, there is no evidence that transgenic markers currently in use pose a health risk to humans or domestic animals. Nevertheless, most organizations have concluded that although the risk of plants transmitting antibiotic resistance genes to pathogenic bacteria is vanishingly small, the use of markers conferring resistance to clinically relevant antibiotics should be phased out as alternative strategies become available.1,2,4,10 Back toTop
Safety of Genetically Modified Crops: The Environment
Modern agricultural practices are often at odds with environmental preservation and may particularly threaten biodiversity. Thus the potential environmental risks of GM crops must be framed in the context of the current use of conventional technologies.
Since 1987, more than 25,000 field trials of GM plants have been carried out in 45 countries without adverse environmental consequences. The relevance of environmental data obtained from small field trials to large-scale sowing on several million acres of land has been questioned; however, it has been estimated that in 1999, 200 million acres of land have been planted worldwide with transgenic crops with no adverse environmental consequences.92 Major concerns relate to the potential for pest resistance, outcrossing with weedy relatives, and reduced biodiversity.
Pest Resistance. Insect resistance to Bt plants has not been reported to date, but the evolution of pest strains that can overcome the pest-protection mechanisms of plants could have a number of potential environmental and health impacts. Occurrence of resistance in field insect populations in response to extensive applications of Bt sprays is rare, but has been reported.93,94 Many scientists, as well as members of environmental pressure groups, believe that continued exposure of pests to Bt plants will inevitably lead to selection for resistance and that the large-scale introduction of Bt crops endangers the durability of Bt as an insecticide, both in crops and sprays.1,11
Several strategies that should prevent or delay the rapid development of resistance to Bt plants have been proposed including the use of multiple toxin genes with different modes of action so that cross-resistance is unlikely to occur; the use of tissue-specific or inducible promoters; and, the use of temporal (rotation) or spatial refuges.95-97 In an effort to delay the development of resistance to Bt toxin, the use of refuges (areas of non-transgenic plants planted close to the transgenic varieties) has been adopted. In theory, plant refugia of non-Bt crops provide Bt-susceptible insects for mating to reduce the probability of homozygote resistant offspring. This strategy is expected to work because resistance is usually a genetically recessive trait; however, results of one study showed that for the European corn borer, resistance is an incompletely dominant trait.98 The environmental importance of this study has been questioned because resistance was not directed to the same Bt toxin as that found in the corn plant, and the ability of the "resistant" population to survive on Bt corn also was not tested.99
An additional concern is based on the finding that insects that eat Bt crops develop slower than non-Bt feeders so they would not be available to mate.100 The overlapping of insect generations may mitigate this concern. A refinement of the spatial refuge strategy is the refuge/high dose-combination, which entomologists consider to be the most promising, and which forms the basis for EPA-directed insect resistance management programs for crops containing Bt toxins.101 The agency has not articulated a general policy indicating when it would require the development of resistance management plans for specific transgenic pest-protected crops.1 Comprehensive insect resistance management is particularly important if a pest protectant or its functional equivalent is providing effective pest control (eg, like Bt sprays) and the growing of a new transgenic pest-protected plant may threaten its utility.
Others believe that the use of crop varieties containing plant pesticides is unlikely to accelerate the emergence of pesticide-resistant insect strains and may actually prevent their emergence when compared to spray applications of similar pesticides. The use of Bt sprays employs a mixture of toxins, and their use creates a more variable dose exposure.
Finally, a recent study has demonstrated that the concept of a refuge works in the field.102 Using a "20% mixed refuge," in which the Bt and non-Bt crops were mixed randomly, compared with a "20% separate refuge," in which a block of non-Bt crops was grown next to the Bt crops, the study showed that a separate refuge would be more effective in preventing the diamondback moth from becoming Bt-resistant by reducing the number of homozygous resistant offspring.102
Effects on Nontarget Organisms. In the field, crops support not only pest insects but also arthropods (parasitoids and predators) that feed on these herbivores and play an important role in the regulation of herbivore populations (tritrophic system). One of the ecological risks of releasing transgenic Bt-plants would be the unforeseen effects of the toxin on organisms that are not pests of the crop itself, especially if those organisms are predators and parasites of pests and therefore of benefit to agriculture. If inbuilt pest resistance is to offer maximum benefit to the environment, then it should not present collateral damage to nontarget species, compared with conventional methods.9
Bt crops containing Cry1Ab, Cry3A, and Cry9C have not had an impact on honeybees, but high concentrations of the Cry1Ab toxin were reported in one study to be toxic to Collembola. Studies performed with other GM corn products that produce the Cry1Ab toxin did not find adverse effects on Collembola.103-106 Lacewing larvae fed on caterpillars reared on one specific variety of transgenic corn (Cry1Ab) had increased mortality compared with those fed on caterpillars reared on nontransgenic corn.107 Reduced fertility has been observed in ladybird beetles fed on aphids reared on potatoes expressing lectin genes.108 Other studies found no detrimental effects of Cry1Ab (contained in pollen from transgenic corn) on insect predators examined (suggesting that the toxin lacks significant direct effects),109 or on insect predators that preyed on crop pests that have eaten Bt crops.110
Recently, a widely quoted laboratory study showed that Monarch butterfly larvae had higher mortality when they ingested high doses of Bt corn pollen that had been experimentally dusted onto milkweed leaves, once again focusing attention on the possibility of harmful effects.111 The EPA recognized that Bt pollen could be toxic to Monarch butterfly larvae, so the main finding of this study was not entirely unexpected. It is generally acknowledged that if Monarch butterfly larvae are fed Bt toxin, whether in corn or from a spray, higher mortality will occur.99 However, Monarch butterflies do not feed on corn plants and could only encounter Bt through incidental feeding on pollen deposited on milkweed, and the concentration used in this study was much higher than could be expected in the field.112 Monarch exposure to pollen containing Bt is low because the Monarch's migratory pattern leads to limited overlap with periods of corn pollen shed, and most of the Monarch population is found in open meadows, prairies, roadsides, and in fields of other crops, rather than in corn fields. A recent study has confirmed that in the field, Bt pollen is rarely, if ever found in high enough concentrations on milkweed to hurt the Monarch caterpillar.113 Mowing roadsides, the use of herbicides, and the destruction of overwintering sites in Mexico pose far greater threats to the survival of Monarch populations than Bt corn.
There have been few published field studies on the effects of Bt plants on nontarget organisms. Those that have been conducted appear to confirm the original assumption that Bt plants either have no effect on beneficial insect populations or their use is associated with increased numbers of non-target insects relative to fields that have been treated with chemical insecticides.1,114,115 Significantly, a new field study showed that the black swallowtail caterpillar, which is just as likely as Monarch caterpillars to encounter Bt corn pollen during critical development phases, had no mortality directly or indirectly attributable to ingestion of Bt pollen under field conditions.116 Monitoring of Bt cotton also has so far failed to show any significant effects on predators, including lacewings.115 The negative side effects on lacewings described in the laboratory107 have not been reflected by reduced populations in the field.115 Accordingly, further field-based research is needed to determine whether crops containing Bt proteins could have harmful effects on the population dynamics of nontarget organisms.1
Creation of Super Viruses. Most virus-derived resistance genes are unlikely to present unusual or unmanageable problems that differ from those associated with traditional breeding for virus resistance; however, a number of issues and concerns emerge when agronomic consequences of using transgenic pest protection strategies against viruses are considered. These center on the possible emergence of new or novel viral strains, introduction of new transmission characteristics, and changes in susceptibility to heterologous viruses when the transgene is expressed. New technology currently being developed to introduce pharmaceuticals into plants via virus-based vector systems will further raise these concerns. However, all of these issues are environmental; there is no risk to human health since plant viruses are consumed routinely in the human diet.2
Gene Flow and Superweeds. Another environmental concern is the possibility of hybridization of transgenic pest-protected plants with neighboring wild relatives.117,118 Crops vary in their degree of reliance on self- or outcrossed pollination; the latter may be insect-, animal-, or wind-aided. Relevant variables include the magnitude and distance of pollen dispersal; persistence of the gene, if transferred, in wild populations; and whether traits increase invasiveness.
Outcrossing plants disperse pollen to other plants and therefore may require greater isolation distances during the initial field testing, prior to regulatory approval to contain the introduced genes in the environment. Genes from one crop plant may be spread to other plants of the same or related species when pollen is transported by wind, bees, or other animal pollinators. The process of gene flow does not pose a hazard itself, but the consequences of gene flow might, and therefore should be assessed prior to commercial introduction.1 Indeed, genes have been flowing from crops to other plants and weedy relatives of crop plants for centuries, but now it is also possible for potential fitness-enhancing transgenes to spread from one crop into another, to noncompatible crops, and to weed populations.1
Weeds (and crops) resistant to one or another specific herbicide have been known for 50 years, and ecological studies of the spread of resistance investigated this in detail 20 years ago.119 Conventional crop genes have spread to wild populations but it is not known whether this has increased weedy invasion.120 It is generally believed that in the absence of selection pressure, a neutral trait may be lost over time. However, results of one study that crossed canola plants carrying the gene that encodes resistance to the herbicide glufosinate with a weedy relative (field mustard) found that the gene persisted in the weed even when no herbicide was applied and the weed produced equally fit offspring.
Although pollen dispersal can lead to gene flow among cultivars and from cultivars to wild relatives, only trace amounts of pollen are typically dispersed further than a few hundred feet. A study conducted in 2000 indicates that the chance of cross pollination between corn plants is small for plants in close proximity to each other and quickly drops to near zero with increasing distance, with no cross pollination occurring at a distance of 1,000 feet.121 Although the transfer of resistance traits to weedy relatives could potentially exacerbate weed problems, such problems have not been observed. Clearly, however, the criteria for evaluating the merit of commercializing a new transgenic pest-protected plant should include whether gene flow to feral plants or wild relatives is likely to have a significant impact on these populations. Since one of the original claimed benefits of GM crops is the reduction of environmental damage, the risk that some GM crops might have detrimental environmental consequences must be studied and balanced against the certainty that more conventional methods will continue to seriously damage the environment.
The commercialization of transgenic crops has increased the necessity of crop-to-weed gene flow studies because many transgene phenotypes have never occurred in wild relatives of certain crops. The consequences of gene flow will depend on which cultivated species are capable of crossing with wild relatives.1 Studies of gene transfer from conventional and transgenic plants to wild relatives and other plants in the ecosystem have so far concentrated on species of economic importance such as oilseed rape, cotton, and corn. An absence of data for some other crops imposes the need to carefully and continuously monitor any possible effects of novel transgenic plants in the field.1 In addition, there is a continued need for research on the rates of gene transfer from traditional crops to indigenous species.
Finally, risk assessments should be standardized for plants new to an environment. Most nations already have procedures for the approval and local release of new varieties of crop plants. Although these assessments are based primarily on the agronomic performance of the new variety compared with existing varieties, this approval process could serve as the beginning or model for a more formal risk assessment process to investigate the potential environmental impact of the new varieties, including those with transgenes.
Biodiversity. There is some concern that GM crops will outgrow the local fauna in the environment to the detriment of native species. Few, if any GM crops are likely to cause this problem.9 Traits normally associated with domestication make crop plants reliant on a managed agricultural environment and thus less capable of competing and surviving in the wild and becoming an invasive weed.11 GM crops, although modified, are (re)introduced into familiar surroundings. Also, crop plants are generally noncompetitive outside their normal agricultural environments because they have been bred with traits to enable their cultivation at the expense of traits that would enable them to flourish in the wild. However, if a gene were introduced to increase the plants' wild competitive ability, there might be a potential to disrupt natural ecosystems.
With herbicide-tolerant crops, the use of environmental herbicides to control weeds early in the growing cycle would reduce the number of weeds in farmlands with the potential for population reductions in native wildlife that rely on them for food. This effect, combined with more efficient killing of insect pests, may result in less food for their predators and other animals on the food chain. However, negative impacts on species that rely on current conventional agricultural practices for survival should not be considered as disruption of natural equilibria. Thus, as stated earlier, risks and benefits of transgenic crops must be balanced against the conventional agricultural practices currently in place.
Concern exists that the effects of insect-resistant crops on nontarget species may further exacerbate the potential problem of a reduced food supply for farmland birds and other wildlife. Currently, there are no data to support this concern; however, more research is needed on this important environmental issue. Until such information becomes available, the creation of refuges of non-GM crops and conservation of headlands may offer redress for these animal species, which tend to feed on weeds around crop lands and not in them.
Gene Flow and Genetic Diversity. There is concern that the introduction of transgenes will lead to a loss in genetic diversity in crops due to aggressive planting of high-yield GM crops. This has not happened with modern high-input agriculture and it has also not happened with the implementation of hybrid F1 maize technology, a scenario that is similar to the current situation with GM crops.
Clearly, there is a continuing need for studies on the possible risks of GM crops to the agricultural environment. Regulations will require dynamic flexibility to respond adequately as new data on GM crops become available.4 Substantial information about their actual effects on the environment and on biological diversity is lacking. As a consequence there is no consensus as to the seriousness, or even the existence, of any potential environmental harm from GM technology. The environmental impacts of transgenic plants, if not neutral or innocuous, must be preferable to the impact of conventional agricultural technologies GM technology is designed to replace. There exists a continuing need for thorough risk assessments at early stages in the development of all transgenic plant varieties, and the institution of a monitoring system to evaluate risks and benefits in subsequent field tests and releases. Back To Top
Consumer-related Issues, Consumer Choice, and Food Quality
Attitude. Most interested observers would agree that: (1) proponents have failed to inform the public sufficiently about this new technology or to convince consumers of the benefits that may accrue from it; (2) opponents have voiced concerns and fears that are often not based on science and without much consideration of the advantages that society might obtain; and (3) the government has failed to articulate a consistent and principled framework for public discussion and analysis.
In Europe in particular, mishandling of the bovine spongiform encephalopathy crisis, intensive negative press coverage, and a resulting lack of public trust in regulatory procedures, have focused attention on the safety of GM foods. The current public mistrust of science, expert opinion, and agriculture that exists in the UK cannot be underestimated.10 GM foods are perceived as having brought little direct benefit to consumers. If the public could see or experience tangible benefits in food, attitudes would be more accepting.122,123 This may occur with some of the products in development, but current applications of transgenic technology have been of most direct and immediate benefit to corporations and farmers, while direct consumer and environmental benefits have been less visible.5
Opponents of GM food understand that diminished understanding and lack of knowledge is the key to obstructing biotechnology. For example, a recent survey of European consumers showed that more than one-third believed that eating GM foods would alter their own genes and almost a half believed that conventional breeding techniques are as effective as transgenic techniques and would yield identical results.123 Finally, there exists no simple way of informing the public impartially about the nature and science of GM crops. Media coverage tends to be inflammatory; preliminary "results" that may be contradicted in later reports confuse the public about the actual facts. An excellent example of this was the press coverage of the negative effects on rats of eating GM potatoes,124 which further analysis revealed to be at best uncertain, and at worst, groundless.125-128
Consumer Choice. Some consumers fear that the proliferation of GM foods will mean fewer choices for the consumer. This has led many supermarkets in the UK to remove any genetically modified ingredients from their own brand products and increased calls for segregation of GM crops from non-GM crops in the supply chain. Interestingly, this action has actually deprived UK consumers who may choose to purchase GM foods of any realistic ability to exercise that choice.
Labeling. In the European Union the debate is not whether GM foods should be labeled, but how they should be labeled. This agenda is driven by a "consumer-right-to-know" perspective, the core of which is the notion that the public has a basic right to know any fact it deems important about a food or a commodity before making a purchasing decision. This contrasts with the approach in the United States where labeling decisions are made to provide consumers the essential information they need to choose foods wisely, and to assure that consumers have the information they need relative to health, nutrition and food safety.
In the United States, the FDA has the authority to require additional key information on the food label if such a requirement is necessary to prevent consumers from being misled or adversely affected.129 For example, the FDA has required that the label of a product identify the presence of an ingredient or ingredients that may adversely affect a consumer (eg, warnings on olestra, sorbitol, phenylalanine, or the presence of ingredients such as peanuts, eggs, milk, etc). However, the agency has a long history of expressly avoiding the imposition of warnings for ingredients that can cause only mild, idiosyncratic responses in consumers to expressly avoid over-exposure to warnings that may decrease the effectiveness of other more important health-related warnings.129
The Nutrition Labeling and Education Act of 1990 (NLEA) fostered the idea of complete nutrition labeling and that the food label should convey meaningful nutrition information about foods in a simple, clear, consistent format. This goal can be achieved only if consumers understand and use the information on food labels. Importantly, not all information related to maintaining healthy dietary practices can be included on food labels. Not only misleading information, but also information that is collateral and unnecessary or that crowds out or overshadows more important information may interfere with consumers' abilities to use the information of greatest public health significance.
Thus, there is a conflict between the "consumer right-to-know" and the "material, meaningful information" labeling philosophies.129-131 Statements cannot mislead or deceive. Labeling may be misleading not only because of what it says but also because of what it fails to say. With voluntary labeling even truthful information could mislead consumers. For example, does touting a food as not being "genetically modified" imply that there is a danger or defect inherent in products that are derived from recombinant DNA sources? Such misleading implications must be avoided and the information presented must appear in its proper context.
Although consumer interest in receiving information is important, consumer interest alone is not enough to justify requiring that such information be included in food labels.129 However, consumer curiosity may be a very compelling reason for manufacturers, processors, and distributors to voluntarily provide truthful, nonmisleading information that the consumer--for whatever reasons--is interested in knowing about the food he or she purchases. Such appears to be the case for GM foods. The FDA recently announced plans to draft a labeling guidance to assist manufacturers who wish to voluntarily label their foods as being made with or without the use of bioengineered ingredients.61 Scientifically, such labeling is useless unless the public is educated as to what genetic modification is.9 If foods are to be labeled, then readily available, explanatory information about genetic modification should be present at the point of sale in all stores carrying GM products.9 Back to Top
In the past half century, the number of people fed by a single US farmer has grown from 19 to 129, but intractable health and nutrition problems remain. The world's population continues to grow even as available farmland shrinks. There is an urgent need for sustainable practices in world agriculture if the demands of an expanding world population are to be met without destroying the environment or natural resource base.6 GM technology, coupled with important developments in other areas, has the potential to increase the production of food, improve the efficiency of production and the nutritional quality of foods, reduce the environmental impact of traditional agriculture, and with cooperative efforts, provide access to this technology for small-scale farmers.
Underpinning the movement against GM foods is a resistance to global agro-business, and the belief that current food supplies are adequate to relieve world hunger if appropriate distribution mechanisms were in place.8 If GM technology is to benefit developing countries, mechanisms must be in place, perhaps through public and private partnerships, to make the technology available to those who can least afford it. Back To Top
Genetically modified foods "raise many issues--scientific, technological, environmental, social, ethical, economic, and political."132 Controversy over GM food exposes larger issues about public trust in science and the role of science in policymaking. In an increasingly complex world, trust functions as a substitute for knowledge. Interference with our systems of food production has always aroused public concern, occasionally with justification. Attempts to introduce GM foods have stimulated not a reasoned debate, but a potent negative campaign by people with other agendas. Opponents ignore common farming practices and well investigated facts about plants, or inaccurately present general problems as being unique to GM plants.
With an abundance of food and extended life expectancy in the Western world has come the demand for a risk-free world. Under these circumstances, "the public is little interested in new ways of producing the same food, especially if there is even a minute health risk."119 The consumer's biggest concern is about risk, especially in light of the bovine spongiform encephalopathy experience; scientists and the regulatory processes are no longer automatically trusted. Risks are assessed differently in medicine and food. The public accepts quite high risks when seriously ill, but will not tolerate much risk at all with food. Complicating the weighing of risk is the question of how much any potential hazards are offset by potential benefits such as reducing the use of chemical pesticides, lowering costs, and improving nutritional value.18
The problem for policymakers is how to articulate policy for the public good when some pieces of the scientific puzzle are incomplete or missing and neither the benefits nor the risks are well-defined. At a minimum, the regulation of GM foods--including the conditions under which they are marketed--should be based on the soundest possible science, while acknowledging the limits to scientific certainty. The best that research can do is narrow the limits on uncertainties, not eradicate them. In reality, it is impossible to encompass all possible interactions in preapproved trials, and postapproval monitoring should be encouraged where transgenic plants are grown on a large commercial basis.
If harmful effects become apparent, they still must be placed in scientific and socioeconomic perspective, keeping in mind that all human interventions to protect crops from pests and land from weedy overgrowth disrupt the tritrophic system. Such effects must be judged alongside conventional agricultural systems and pest control methods.
Also required is a method of facilitating public access to credible scientific information and of communicating in a responsible form both its significance and its limitations. Importantly, broad public concerns must be taken into account in food safety regulations if they are to maintain credibility. By addressing environmental concerns and consumer demands with improved risk management and appropriate labeling, industry may be able to ease its path for introducing GM foods into worldwide markets.133 Back to Top
RECOMMENDATIONS (Adopted AMA Policy)
The following statements, recommended by the Council on Scientific Affairs, were adopted as AMA policy at the 2000 AMA Interim Meeting:
- The AMA recognizes the continuing validity of the three major conclusions contained in the 1987 National Academy of Sciences white paper "Introduction of Recombinant DNA-Engineered Organisms into the Environment."
- Federal regulatory oversight of agricultural biotechnology should continue to be science-based and guided by the characteristics of the plant, its intended use, and the environment into which it is to be introduced, not by the method used to produce it, in order to facilitate comprehensive, efficient regulatory review of new genetically modified crops and foods.
- The AMA believes that as of December 2000, there is no scientific justification for special labeling of genetically modified foods, as a class, and that voluntary labeling is without value unless it is accompanied by focused consumer education.
- The AMA supports efforts for the systematic safety assessment of genetically modified foods and encourages: (a) development and validation of additional techniques for the detection and/or assessment of unintended effects; (b) continued use of methods to detect substantive changes in nutrient or toxicant levels in genetically modified foods as part of a substantial equivalence evaluation; (c) development and use of alternative transformation technologies to avoid utilization of antibiotic resistance markers that code for clinically relevant antibiotics, where feasible; and (d) that priority should be given to basic research in food allergenicity to support the development of improved methods for identifying potential allergens.
- The AMA supports continued research into the potential consequences to the environment of genetically modified crops including the: (a) assessment of the impacts of pest-protected crops on nontarget organisms compared to impacts of standard agricultural methods, through rigorous field evaluations; (b) assessment of gene flow and its potential consequences including key factors that regulate weed populations; rates at which pest resistance genes from the crop would be likely to spread among weed and wild populations; and the impact of novel resistance traits on weed abundance; (c) implementation of resistance management practices and continued monitoring of their effectiveness; and (d) development of monitoring programs to assess ecological impacts of pest-protected crops that may not be apparent from the results of field tests.
- The AMA recognizes the many potential benefits offered by genetically modified crops and foods, does not support a moratorium on planting genetically modified crops, and encourages ongoing research developments in food biotechnology.
- The AMA recognizes that the government, industry, and the scientific and medical communities have a responsibility to educate the public and improve the availability of unbiased information on genetically modified crops and of research activities.
- The AMA rescinds Policy H-480.985.
The following statement, recommended by the Council on Scientific Affairs, was adopted as an AMA Directive at the 2000 AMA Interim Meeting:
The AMA will monitor the forthcoming final rule for plant pesticides from the Environmental Protection Agency and respond as appropriate.
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References
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Resolution
Resolution 512 (I-99), introduced by the Washington Delegation at the 1999 Interim Meeting, and adopted by the House of Delegates, asks:
That the American Medical Association study the issue of genetically modified foods and issue a report back to the House of Delegates. Back to text
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