The safety issues related to new foods created by biotechnology were, until comparatively recently, reasonably clear. In general, food plants produced by modern plant breeding techniques were subject to no specific controls. However, the discovery that a new variety of potato (Lenape) with good agronomic characteristics contained higher than average levels of the potentially toxic alkaloid solanine was sufficient grounds to withdraw it from commercial use. Similarly, in Sweden the variety Magnum Bonum was found to contain potentially toxic levels of glycoalkaloids and was withdrawn (55). In a number of countries, this led to voluntary codes of practice being adopted with the plant breeding industry to ensure that if there was more than a 10-20% variation in composition, the product would be referred to food safety agencies for evaluation.
As far as plants subject to genetic engineering are concerned, the principal concerns have been focused around the potential allergenicity of the modified plant and the use of antibiotic resistance genes for the selection of new strains. The possible variations in overall composition and the position to be adopted in terms of the need for safety evaluation have been considered by a number of international bodies.
In 1991 the United Nations Food and Agriculture Organization (FAO) and the World Health Organization (WHO) (56) convened an expert panel to consider strategies for assessing the safety of foods produced by biotechnology. The expert panel recommended that genetically engineered foods should be evaluated for safety by comparison with that of their natural antecedents. If the composition was similar to that of the traditional food and this food had a safe history of use, then the genetically modified food would be regarded as safe.
This led to the concept of "substantial equivalence" being developed following a meeting of the Organization for Economic Cooperation and Development (57). This concept assumes that if a genetically modified food can be characterized as substantially equivalent, it can be assumed to pose no new health risks and can be marketed without the need to undertake extensive toxicological and nutritional studies to determine its safety in use.
The principle of substantial equivalence has been adopted into the European Union (EU) Regulation on Novel Foods and Novel Food Ingredients (58). The Regulation excludes from its controls foods and food ingredients obtained through traditional propagating or breeding practices and which have a history of safe use. Genetically modified plants are considered as "novel" under the terms of the Regulation. However, the detailed safety evaluation provisions of the Regulation do not apply to foods produced by genetic engineering "if on the basis of the scientific evidence available they are substantially equivalent to existing foods with regard to their composition, nutritional value, metabolism, intended use, and the level of undesirable substances present." The Regulation regards food as novel if the characteristics of the food differ from the conventional food having regard to the accepted limits of natural variation of such characteristics. However, the principle of substantial equivalence is vague and difficult to define in many cases.
The U.S. attitude to regulation has so far been to regard safety as an issue that relates to the characteristics of the food and not to the process(es) that leads to it. Novel food products, of which products produced by genetic engineering are included in the definition, are not subject to any specific approval on safety grounds if the constituents of the food are the same as or substantially similar to those of substances currently found in other foods.
It is clear that it is never going to be possible to argue that a genetically modified plant is safe any more than to argue that a plant produced by conventional plant breeding is safe. The very concept can be addressed only in the context of a history of safe use as a human food. Clearly, the overwhelming evidence supports the view that health benefits arise as a consequence of the regular consumption of a variety of fruits and vegetables, few if any of which have any close compositional relationship to the wild types from which they were bred. Similarly, their production, storage, and distribution have depended on the use of a wide range of chemical fertilizers and pesticides. These chemicals are extensively tested for safety before approval is given for their marketing and use, but this has not removed the widely held view among consumers that "organic products" are better for your health. There is no evidence to support this view, and any adverse health effects that there might be as a consequence of the use of pesticides appear to be outweighed by the beneficial effects from the consumption of fruit and vegetables. What determines "safety" is the overall effect of consumption over a period, not the effects of a specific chemical that might be present.
The historic approaches to assessing the safety in use of a chemical in the food supply continue in spite of the fact that a growing body of evidence suggests that this is an inappropriate way to assess the safety of a chemical that may be present in the diet in only trace amounts (59,60). Animal feeding studies of fundamentally benign foods cannot be used to determine a dose-response relationship as in the case of a single chemical. Their usefulness is severely limited because of the differing diets of animals and the need to ensure that test and controls do not differ because of differences in weight or nutritional balance.
Many of the phytochemicals that are present in plants might be judged to pose an unacceptable risk if they were subject to the same approval procedures as are applied for synthetic chemicals (61). The value of doing so is highly questionable. It seems clear that any possible adverse effects of these phytochemicals are neutralized by other protective phytochemical factors in the plant.
It is possible that the standardized toxicological bioassays do not reflect the mechanisms that are operating in vivo through low-dose exposure to these compounds in the environment of the food. The past application of toxicology to food chemical risk assessment provided a generalized basis for protecting the population. Such a risk assessement process was strongly influenced by the need to ensure that there were no risks to consumers from the ingestion of food chemicals that were to be used in the production and processing of food. Thus, the only factor to consider was the inherent toxicological properties of the compound in question. The inherent toxicological properties of the compounds already in food and the influence they might exert in altering the toxicity of the added chemical were not considered. Neither was it deemed of interest to determine whether, or under what circumstances, the same chemicals might exert some health benefit as opposed to risk.
Although the safety in use of any food produced by genetic manipulation would be based on nutritionally based experimentation, there is likelihood of an insistence on applying traditional animal toxicological bioassays that have been designed to assess risk and not to make risk-benefit assessments. This is especially so if the food is judged not to be compositionally identical to the "traditional food." The assumption that chemicals, be they natural or synthetic, must pose a health risk of some kind, no matter what the dose, should be challenged. Risks can arise when exposure to chemicals is high. But it does not follow that there is some degree of residual risk when exposures are low.
It is beholden on scientists to demonstrate that this is so through rationally based arguments that have a biological validity. Risk evaluation using animal bioassays invariably applies rules that overemphasize the likely risks. The process highlights low-level risks and is costly in terms of both manpower and the use of experimental animals. The process might be justified if it resulted in providing consumers with total security over the safety in use of a food or of a chemical, but this is not the outcome. The very use of the word "risk" implies something unacceptable to many consumers. The application of extensive and rigorous approval procedures has done little to provide consumers with a sense of security in consuming food produced by using chemicals or other technologies.
None of the present methods for assessing safety take into account the fact that food is a complex mixture of chemicals, each of which has the potential to alter the overall risk-benefit ratio of consuming that food. Assessing the "risk" of chemicals in isolation and ignoring any assessment of "benefit" does not inspire confidence in the scientific process. Lack of confidence in the scientific basis for regulating chemicals produces a lack of confidence in the regulatory process itself. Unfortunately although it is ac cepted that animal toxicological bioassays will play a diminishing role in establishing the "wholesomeness" of a food, there are presently no alternative or viable substitutes. There is an urgent need to develop procedures for the safety evaluation of chemicals in food that are more realistic and that are developed from an understanding of the mechanisms that are occurring at usual exposure levels rather than on an empirical description of the phenomena and a focus entirely on perceived risk. Failure to do so will provide arguments for the opponents of any uses of genetic modification to impede progress toward its use in the development of even healthier plant foods.
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