Peggy G. Lemaux, Ph.D.
University of California, Berkeley
SLIDE 1 Claims are often repeated by those opposed to biotechnology that the products produced commercially are "Untested" for food and environmental safety. The focus of my talk will be to explore some of these claims by looking at these products and discussing some of the issues that have surfaced relating to their safety.
SLIDE 2 First it might be instructive to look at the differences in attitudes between U.S. and European consumers and why these differences occurred. There is no simple explanation.
The differences began to surface in the late 1990's. Why did it happen then? At about that time there were several food safety scares in the E.U., e.g., mad cow disease and dioxin-contaminated foods. The credibility and effectiveness of the regulatory agencies during and after these events was, I believe, an important factor in consumer decisions made about GE foods. People were nervous about food safety. U.S. consumers recently had a glimpse into such a frenzy by watching what happened when a cow with BSE, or mad cow disease, was identified here. SLIDE 3
In Europe in the late 1990's consumer confidence in the ability of the federal agencies to insure food safety was not strong. At that time decisions by officials were perceived by many as being based on politics, not public safety. There were, of course, other factors that contributed to the controversy. SLIDE 4
But the outcome was that many European consumers were nervous and questioned whether government officials would adequately judge GE food safety.
How Do U.S. Consumers Feel about the New GE Foods?
These factors in Europe certainly influenced attitudes of E.U. consumers. But how do U.S. consumers feel about these foods - then and now? SLIDE 5 First it is important to know that even as late as April 2003, when asked if there "are any foods produced through biotechnology in the supermarket now?" 34% of U.S. consumers said "no". This number differs little from that seen in a survey done in 1997 in which 37% said "no" (IFIC, 2003). This lack of awareness may be because of a lack of interest or to the fact that Americans have too many other issues on their "radar screens".
Another indication of Americans' attitudes toward GE foods is revealed in surveys that ask consumers to identify food safety concerns. SLIDE 6 In 2003 one such survey (and there are many) only 1% of those polled expressed concern about the safety of genetically engineered foods, down from 2% who expressed that concern in Jan. 2001. Of more concern were safety concerns related to food handling and preparation, where 41% of respondents expressed concern.
Another possibility for the difference in opinion between what European and U.S. consumers consider an important food safety issue relates to the fact that the majority (not all) of U.S. consumers maintain trust in federal agencies to assure food and environmental safety. SLIDE 7 Again consumer polls indicate that respondents have confidence in the U.S. Food and Drug Administration, the regulatory arm responsible for food safety and which monitors the safety of the new GE foods. In a Gallup poll, 75% of Americans had either a great deal or a fair amount of confidence in the federal government to ensure food safety; only 5% had none.
What Are the Issues?
So what are some of the issues surrounding the application of genetic engineering technologies to agricultural crops? SLIDE 8 In general they fall into three broad categories, food safety, environmental safety and socioeconomic/ethical issues. I will try to touch on the major topics in two of these three areas.
Before discussing this, I have to admit that, as a scientist, I was not aware of the distinction between "risk" and "safety" and it is important to understand this when discussing safety issues. Risk per se can be determined quantitatively by testing foods in various different ways. SLIDE 9 "Safety" is only partly quantitative since it is defined as acceptable risk. Based on an individual's values and perceptions, they will decide if they feel that something is safe. The corollary is that most products of technology are not black and white safety issues; there are plusses and minuses.
What are some of the food safety issues?
1) Introducing Allergens. SLIDE 10 An often cited example of the potential for this risk is work conducted at Pioneer Hi-Bred in the 90's to improve protein quality of soybean. They used a naturally occurring Brazil nut protein, which improved the amino acid imbalance in the soy nut. During development, however, Pioneer scientists discovered that some individuals had allergies to this protein based on blood serum assays and it never entered the marketplace. But this issue is still raised. In fact in a recent letter to the editor in Mendocino County California, a resident speaking in favor of Measure H, which will ban the growth and propagation of GE plants and animals in the county, raised this issue. SLIDE 11 It was stated that 10 people died from eating this GE food - even though it never left the laboratory!
Does this example show it is possible to move an allergen from one food to another? Yes. Was this a surprising finding? No. This example also shows that the development process for a GE food involves steps that allow the identification of a food safety problem before the food is marketed.
Since we are talking about risks and benefits, it should also be noted that genetic engineering could be used to eliminate allergens. This approach has not yet been fully explored but, for example, in China, where rice allergies are common, researchers identified a major allergen and worked to create rice varieties with reduced levels of the protein that were less allergenic for consumers. SLIDE 12 In the U.S. work is focused on removing allergens from for example wheat, peanut and milk.
What U.S. governmental agencies are responsible for overseeing the potential for allergenicity in GE foods? SLIDE 13 First, if a piece of genetic information is introduced into a GE food from a source known to cause allergies, e.g., peanuts, wheat, fish, milk, the product must be labeled as such under current FDA statutes. Second, companies under FDA scrutiny do extensive, although nonmandatory, testing of GE foods to assure safety. This testing involves assessing potential allergenicity using predictive models and, if necessary, animal testing. Such testing does not result in zero risk, but it reduces the probability of adverse consumer reactions. SLIDE 14
Another example of an allergenicity problem related to GE foods containing Starlink corn, which had a protein designed to protect against insect damage. SLIDE 15 Because of questions regarding some of its characteristics, federal regulatory agencies approved it only for animal feed, not for human consumption. Some grain got into certain corn products, which were recalled because agencies were not convinced that this new protein would not cause allergies.
Was this a danger to consumers at the time of its market withdrawal? No, allergists know that a person has to eat a lot of a protein over a period of time to develop allergies and this product was removed from the market before that could happen. Later studies showed that this protein had only a moderate chance of causing an allergic response. Did the presence of Starlink corn in food products show that there were weaknesses in the ability to segregate grains during their movement to market? SLIDE 16 Yes, this showed that grain intended for animal feed could not be segregated properly from grain intended for human consumption. This was critical to learn before plants making pharmaceuticals or plastics enter the market.
2) Inadvertent Creation of Allergens or Toxins. SLIDE 17 Can we predict or assess this type of situation with 100% accuracy. No. But, is this a situation that would only occur with GE foods? No. For example, the development of both new celery and potato varieties by classical breeding has led to foods with high levels of phytotoxins (psoralen and glycoalkaloids, respectively). When this was discovered during routine testing prior to market release, development of these varieties was stopped, just as in the case of the GE soy with the Brazil nut protein.
That inadvertent development of allergens in foods is not limited to GE foods is also shown by the kiwi, which was introduced into the U.S. in the late 1960's. SLIDE 18 Although not obvious when first introduced, this fruit was later found to cause allergies in certain individuals. In some cases this proved fatal to patients with kiwi allergies because of unexpected cross-reactions with latex rubber. Should foods like the kiwi undergo a decade or more of testing to insure that such allergenicity problems do not occur? A difficult question.
One might then ask if the probability that an unexpected allergen will occur in a new GE food is higher than it would be with a food created by, for example, classical breeding between wild and commercial species? In my opinion, no. It is no more likely that the insertion of a new gene at a random location in the plant genome would activate some previously unforeseen compound than that it would be to occur during the random rearrangements and movement of genes during a classical breeding cross. So although the risk is not zero, it is no greater than with conventional breeding techniques, such as occurred with celery and potato.
3) Horizontal Gene Transfer and Spread of Antibiotic Resistance Genes. SLIDE 19 Horizontal gene transfer means the transfer of genetic information from foods to other organisms, like bacteria and humans. Consideration of these issues requires generation of sufficient scientific data and some data have been published in the scientific literature. First, during the process of digestion most proteins and DNA from foods are broken down. Analysis of experiments in which rats are fed large quantities of DNA indicate that, although the genes can reside transiently in the outermost cells of certain organs like the liver, their retention is not stable and has no observable consequences. Such processes have happened during the entire time humans have eaten foods - and their DNA - and few of us have taken on characteristics of the foods we eat!
Second is the concern over transfer of antibiotic resistance genes in GE plants to gut bacteria. While this has been shown to occur at very low rates under certain unusual circumstances, this is not likely to result in significant problems. Most antibiotic resistance genes are not effective against antibiotics in current clinical use and, besides, the use of resistance genes in generating GE plants is being phased out. Does this mean that eating foods with antibiotic resistance genes is zero risk? No, but it is likely not a significant problem. That antibiotic resistance in gut bacteria is a worldwide problem is irrefutable, but the most significant causes of this problem are not GE foods. They are due to animal husbandry practices and indiscriminate use of antibiotics in human health. SLIDE 20 The likely impact of the presence of antibiotic resistance genes in the new GE foods, if it occurs, will be negligible. This does not mean we should ignore the issue, but we should not lose focus on issues that are more critical to addressing the problem.
With regard to environmental issues, numerous questions have been raised regarding GE crops. SLIDE 21
1) Unintended effects on insect or pest populations. SLIDE 22 This issue first arose with the well-publicized Nature paper by John Losey on the effects of certain Bt
corn pollen on Monarch butterflies. In this paper, laboratory studies were conducted where the fate of Monarch larvae was determined after they were fed leaves dusted with pollen from control, Bt- or non-Bt-containing corn. In this study the insects were not offered a choice of diet. Analysis of data showed that larvae consuming Bt pollen were more adversely affected than those that did not.
This result was not surprising to most scientists since the particular Bt used is known to affect this type of insect (lepidopteran) larvae. In fact it was likely not surprising to the company who created it since they conduct studies prior to release of effects on unintended pests. SLIDE 23 Extensive testing does occur that includes six unintended pests, including the lacewing; however, Monarch larvae were not among those tested. But most knowledgeable scientists in the field would have predicted Monarch larvae would be affected. But testing done by companies is not available for most scientists to see so this paper brought this issue to the fore.
But just how significant a problem might this be? Several pieces of information are pertinent to this question. First, the single GE event used in the Losey study contained Bt in the pollen; other events did not. A large-scale study was conducted after the Losey publication to assess how significant the problem was. SLIDE 24 In those experiments, researchers found that pollen shed in most (not all) areas of the country does not occur simultaneous with larval feeding. Second, Monarch butterflies prefer to lay eggs on milkweed (their preferred host) in the open, not plants located in the middle of a cornfield. Also, the density of pollen needed to kill larvae occurs only within ~ 9 ft of the edge of the field.
Does this mean that Monarch butterfly larvae would not be affected by Bt corn pollen? No. Does this mean that this is not likely to be a major threat to Monarch butterfly populations? Yes. Does it mean that we should not be concerned about secondary effects of pesticidal strategies? No, just as we should be concerned with environmental effects of other strategies, like pesticides, used to control pests.
An interesting contrast to the Monarch butterfly story, that once again emphasizes the need for risk/benefit analysis, is another less well-reported study also published in Nature that demonstrated a positive effect of Bt on beneficial insects. In this case they looked at the effects of Bt canola on a parasitic wasp that infects a major canola pest, the diamondback moth. SLIDE 25 This study found that the populations of beneficial parasitic wasps rose in areas with Bt canola, probably due to the decrease in pesticide use that otherwise reduced the wasp populations.
The question for many is the relative effect of Bt on Monarchs and other unintended pests vs. agricultural practices. SLIDE 26 One of the problems in interpreting such data is the issue of to what these impacts are to be compared. Should the Bt corn be held up against a zero-risk paradigm where agriculture has no effects on the environment, to the methods used by production agriculture or to the practices of organic agriculture? Much of the debate, I believe, revolves around this issue.
2) Creation of Weeds Resistant to Herbicides. SLIDE 27 Is there a possibility of creating weeds that are resistant to the herbicides being used for the herbicide tolerant (HT) crops? It is not a question of whether it will happen; it already has in several places in the U.S. and Australia. This proves once again that overuse of a particular pesticide can, if not carefully monitored, render a new chemical or technology useless? Will this create an ecological disaster? In my opinion, no. Other, perhaps less environmentally friendly herbicides, can be used instead to control the weeds. But it will be a problem for companies developing the crops and for farmers who want to use them!
3) Movement of Genes to Other Plants. SLIDE 28 Could the passage of genes from GE crops to weed species lead to the development of a "superweed"? It depends on how you define the term. Certainly the passage of genes from plant to plant will happen. In the U.S. the major crops like soy, corn and cotton do not have wild relatives, but in some cases they have wild relatives with which they could outcross. And in some cases, like canola, sugarbeet, sunflower, rice and oats, these relatives are control problems.
So is it possible that a gene could escape to one of these wild relatives? Yes, it is likely. Will this be a problem? It depends on the trait, what characteristic it confers and what the crop and weed species are. Let's look at rice as an example. So-called red rice is a problem for rice growers and it can outcross with cultivated rice. SLIDE 29 The movement of herbicide tolerance to these varieties would make it impossible to control red rice with the herbicide used against the commercial variety with the resistance gene. But returning to practices used before the introduction of these varieties could control the problem.
So is the movement of herbicide resistance to red rice likely to create a "superweed" that cannot be controlled with herbicides? No. But it would be a problem for farmers and for the companies developing these varieties because the original herbicide used on the HT crop could not be used. For this reason it is something we should attempt to control if we want to continue using them.
The potential impact of the movement of a particular gene should be judged on a case-by-case basis. For example if the genes that moved into red rice were responsible for increased vitamin content or reduced allergenicity, this would not raise the same environmental safety issues as the herbicide tolerance gene.
The area in which the gene movement occurs is also an issue. In areas of genetic diversity, crops with certain traits should not be released. Or the plants should be engineered so they don't pass the trait on to wild relatives, by creating male sterile plants or putting the trait in the chloroplast genome, which slows the rate of movement to other plants. An example of genes escaping in an area of genetic diversity was raised by a study published again in Nature. SLIDE 30 Here an engineered gene was reported to have escaped into the landraces of corn in Mexico, an area of cultural diversity for this important crop. Again an issue to be considered is the impact of the particular gene on the landrace.
Another possible impact of gene movement involves the passage of genes to organically grown crops. In the U.S. federal policy, developed by organic farmers themselves and now overseen by the USDA, states that GE crops cannot be designated as "organic". Therefore, although genes have moved from conventional crops to organic crops for years, movement of engineered genes from conventionally grown farms to organic farms can cause problems depending on the situation. SLIDE 31 Like pesticide drift, this is an issue that can and will have to be addressed.
In summary, farmers have found GE crops, in general, to improve their bottom line. For farmers, the environmental issues raised by GE crops are not markedly different from issues with which they had to deal with conventional crops. Given consumer support, farmers will likely embrace these products if they deliver benefits. SLIDE 32 If either does not materialize, farmers will return to methods used in the past. Many of the products currently in the fields and laboratories will not achieve the potential necessary for user or consumer acceptance. But the strategies will likely be improved and refined, just as the computer moved from a machine that took up city blocks to one that fits on your wrist. And consumer perspectives on the issue may also change with time. So some products of the technology may find favor with users and consumers; some will not. Some will be a commercial success; some will not.
For a copy of the talk and slides, scientific references and more information, visit ucbiotech.org in the Resources, Scientific Database and Biotechnology Information sections, respectively. SLIDE 33