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Assessing Benefits and Risks of Genetically Modified Organisms


The term "Genetically Modified Organism" or GMO has been applied to plants and animals in which techniques of recombinant DNA have been used to introduce, remove, or modify specific parts of the genome of an organism. The resulting organism may now stably express a novel protein, a protein with novel properties, or carry a change in the regulation of some of its genes. Usually, such a change is designed to improve the ability of the organism to grow, for instance by resisting pests or using nutrients more efficiently, or to improve the usefulness of the organism to us, for instance by improving its nutritive value, by using it to manufacture pharmaceutically important molecules, or employing it to carry out environmentally important processes such as digesting environmental toxins.

Public discussion of the risks of Genetically Modified Organisms turn on a number of different and not always related issues. The discussion document below is meant to serve as an outline of the most important scientific points for many of these issues and to provide references to more detailed discussions of the subject. This document explicitly does not address the social and economic impact of the use and commercialization of GMOs.

Some general issues to consider:

1. A new technique such as genetic engineering may allow novel products to be produced, but there is no scientific basis for the technique used to initially generate the plants or animals to be a source for concern. Therefore, it will be necessary to consider products on a "case-by-case" basis. In some cases, a GMO may not be different in any significant way from a classically bred organism; in most cases, the differences from a parent organism will be more defined and better understood than in a classic breeding experiment.

2. In a given case, is the concern about the organism's interactions with the environment while it is growing, or about the interaction of a product with the user? Both are possible, but if only one is of concern in a given case, the solutions are rather different. Particularly in the latter case, the levels of the novel material should be relevant to determining risk. As detection methods for GMOs per se become more and more sensitive, it becomes possible to detect very small quantities of a GMO. The distinction between a small contamination with an organism able to propagate itself and a small contamination by a protein or metabolic product, in a form no longer able to propagate itself, should be kept in mind. The primary focus of concern lies with invasive, self-propagating organisms.

3. Some of the concerns about GMOs reflect general concerns about loss of genetic diversity and dependence on large companies for seeds and other materials. These are scientifically and socially valid concerns that are worthy of discussion, but are not the subject of this document. From the viewpoint of geneticists, reduction in genetic diversity of crop plants, for whatever reason, can increase the risk of invasion by a single virulent pathogen. Solutions to the problem of loss of genetic diversity, which are not unique to GMOs, are quite distinct from the possible solutions for organisms believed to pose a direct threat to us or to the environment. There is nothing about GMOs, per se, that limits the genetic diversity of food crops, and it is possible that heirloom strains could be revived with this technology.

4. Have both risk and benefit been considered in evaluating concerns? It is never possible to totally eliminate the unknown complication, even when using plants and animals that arise naturally and have been in use for many years. A sense of proportion needs to be maintained in evaluating the nature of the expected benefit and the nature of the possible problems.


I. How does a "GMO" differ from the product of traditional methods of breeding and selection?

One of the arguments generally advanced in support of GMOs is that all of the plants and animals used today in agriculture and manufacturing processes are the result of years of selection and breeding. Specific traits were chosen while others were discarded. This is what one might call conventional genetic modification or breeding, in which we choose what we want out of the many random possibilities arising from mutation and the natural exchange of genetic information. Over the past century, the definition of conventional (or natural) breeding was expanded to include crosses between distantly related species, forced hybridization by cell fusion, and mutagenesis. In general, crops produced by these methods are not regulated, genetic test crosses are not required, and there is little effort to characterize changes in traits unrelated to the property of interest. For GMOs, the changes are specific and directed, so that we know what they are. In addition, however, the limits of what can be changed are much broader. Genes from animals may normally enter plants (and vice versa) in limited quantities under very special circumstances; genetic engineering allows specific genes to be stably expressed in a plant, possibly at high levels. Therefore, while it is not always the case, frequently a GMO will have genetic information we would be surprised to find by classical genetic manipulation methods.

It is important, however, to keep in mind that it is not the method of introducing foreign genes by molecular techniques per se that is likely to make a given GMO different from anything that might have appeared or has appeared naturally, but the nature of the specific change that is made. Therefore, a scientifically valid evaluation of risks (and benefits) needs to be tailored to the specific plant and/or product that is under consideration; the properties of one GMO are unlikely to be shared by another. Much of the concern by scientists about labeling reflects the emphasis that has been placed on every GMO, that is, on the method of construction per se, an issue which is not scientifically supportable. Labeling to indicate significant changes in the composition of the final product, independent of the method of construction, would be a scientifically valid approach to this issue, and indeed is currently required by the Food and Drug Administration (FDA).

II. Can we evaluate whether or not a given GMO is likely to pose unexpected (or expected) risks that should limit its use?

From the beginning of the use of recombinant DNA or genetic engineering, first in bacteria and eventually in plants and animals as well, there has been active discussion of whether these methods might lead to unexpected properties of the engineered organisms and whether those properties might be harmful. The Recombinant DNA Advisory Committee of the National Institutes of Health (NIH) first developed guidelines in 1976 for assessing these issues and for working safely with organisms in laboratories. The general principles developed by that committee and put to the test for the last two decades are directly relevant to the issues discussed here, with one major addition. Initially, recombinant DNA was for use in the laboratory, and while some engineered organisms might be expected to escape the laboratory environment, they were generally not designed to thrive and establish themselves outside the laboratory. More recently, as this technology has been applied to plants and animals, many of these organisms have been specifically designed for use in agriculture or the environment, where the laboratory ideas of containment are not relevant. Therefore, the evaluation of risks and benefits needs to take this into account, and is the basis for many of the concerns about general use of this technology.

A. What needs to be evaluated? Are the methods for carrying out adequate evaluations available?

Here is an outline of the types of questions that are asked in evaluating the possible risks of introducing a new organism: The general question is: In what ways might the introduced changes expand or contract the possible properties of the final product, with what possible consequences? For an example of an in-depth analysis of a specific postulated risk of one type of GMO, see the set of studies published in the Proceedings of the National Academy of Sciences, vol. 98, issue 21 (2001), assessing the risk to the Monarch butterfly population from corn expressing Bacillus thuringiensis (Bt) toxin. These studies conclude that the risk of all but one sort of the currently used corn containing Bt toxin to the overall Monarch population is negligible. Note that risk assessment per se does not consider expected benefits, an important part of the equation as well.

1. As a living organism:

a. Is the new gene expected to change where this organism can grow? How fast it grows? Is it likely to change the organism's ability to exchange genetic information with other organisms?


b. Will this new gene be exchanged/spread to neighboring organisms by any of the currently understood mechanisms? Is it likely to be expressed in the new context? What might the consequences of that be?


c. Is the engineered organism supposed to affect other organisms (act as a pesticide, for instance?). If so, how specific is its action? How specific are alternative treatments? Will the capacity of this organism to grow and spread affect the evaluation of effects on other organisms?


d. How stable are the properties of this organism? Would a simple change that might be expected to arise during wide-spread growth increase the concerns about the properties of the organism?

2. As a food/other preparation:

1. Is the new gene/other modification expected to produce a change in the protein composition of the final product? What new protein(s) should be produced? Would they be expected to be biologically active in the final product? After ingestion/appropriate use of the final product? Would they be expected to be allergenic in the final product?

2. How much of this material should be present in the final product? A very small amount of a potentially harmful product should be considered differently from a large amount of the same product.

B. What is the process for evaluating organisms to be used in the environment?

The current process of evaluation and approval of organisms is described in great detail in the pertinent documents prepared by the relevant regulatory agencies. This is well summarized on the web site, which also provides links to the specific agency regulatory documents. A brief summary is provided here:

1. Department of Agriculture (USDA) process: covers plant pests, plants, veterinary biologics

a. Notification required of intention to field test, including characteristics that suggest no toxicity or pathogenicity for non-target organisms stability; if less characterized or more questionable crops/genes, more information must be provided

b. To commercialize, data on effects, possibilities of spread, etc. must be provided.


c. USDA can retract permission if there is evidence plant is becoming a pest.

2. Food and Drug Administration (FDA) process: covers food, feed, food additives, veterinary drugs, human drugs and medical devices

a. Notification by developer to FDA 120 days before marketing, and producers are required to prove product safety, including information on allergenicity. Additional testing will depend on expectations of harmful ingredients, new ingredients, antibiotic resistance, etc.


b. FDA has authority to remove food from market if deemed unsafe.

3. Environmental Protection Agency (EPA) process: covers microbial/plant pesticides, new uses of existing pesticides, novel microorganisms used commercially.

a. Reviews data on nature of product, its risks and benefits.


C. How do we assess relative risks?

In some cases, the "precautionary principle" is often applied to new technology, asserting that if there is any risk at all to a new technology, then that technology should be avoided. Another method of assessing new technology is to apply the standard of relative risk assessment in which current methods are compared to the proposed technology. With regard to genetically modified foods, this avenue has led to the consideration of the risks relative to conventional breeding and current agricultural practices. For example, if one variety of a plant contains a gene for herbicide resistance that was identified by mutagenesis and selection, and another variety contains a gene (or even the same allele) that was introduced by recombinant technology, is the relative risk of using these plants different? A more complicated issue arises when disparate comparisons are required: Does the risk of spraying chemical pesticides on crops outweigh the risks of introducing crops containing genes that confer pesticide resistance biologically?


III. Putting GMOs in perspective:

Every year, thousands of Americans become ill and die from food contamination. This is not a consequence of using GMOs, but instead reflects contamination from food-borne bacteria. "Natural" food supplements are widely used but are generally not well-defined, purified, or studied. As of 2000, 53% of the US soybean crop, 65% of the corn crop, and 80% of rennet cheese was genetically modified. As of this writing, we are not aware of any confirmed illnesses or other harmful effects resulting from genetically modified foods. Although recent reports of contamination of corn meal by GMOs not approved for human consumption led to several claims of allergic response, to date, none of those individuals has been shown to contain antibodies to the GM protein.




A comprehensive set of information and links to other sites can be found at:


National Academy of Sciences report
Genetically Modified Pest-Protected Plants: Science and Regulation


US and other Government sites describing regulatory process and evaluation of risks and benefits:

United States Regulatory Oversight in Biotechnology:


General outline of roles of various government agencies.
Roles of specific agencies:

USDA Agricultural Biotechnology Information

U.S. Food and Drug Administration, Bioengineered Foods page

U.S. Environmental Protection Agency Biopesticide Web Page

U.S. House of Representative, Committee on Science

The report "Seeds of Opportunity", released in April 2000, assesses the benefits and risks of genetically-modified crops and foods.

Report of the New Zealand Royal Commission on Genetically Modified Organisms

Document developed by GSA Board of Directors, November, 2001.