增進不少對基因食物的認識...
There is conventional wisdom that genetic engineering will tremendously affect life in the 21st century. This technology, in fact, carries implications and impacts that are unprecedented in human history. It will permeate more and more aspects of human life, from reproduction and the cure of diseases, to solutions for the environment, to name but a few. Yet genetic engineering does not only comprise benefits, such as the opportunity to combat incurable illnesses, but also threats that, perhaps with the exception of nuclear energy, are unparalleled within today's society.
These menaces are primarily represented by the transgenic agriculture and the breeding of genetically engineered animals for nutritional purposes. Such kinds of practices are to be prevented for reasons that range from risks to human health and to the environment, to socio-economic aspects and to the fight against world hunger. In this article, we will examine the first two: the dangers to health and to the environment.
In spite of the constant reassurances provided by part of the scientific world and the political establishment on the harmlessness of GE foodstuffs, the consequences for human health still remain obscure.
Transgenesis – the process to create a genetically-modified organism (GMO) – consists of lab interventions which, through the insertion of genes and other hereditary sequences, aim to modify the organisms' genetic makeup. While this technique is relatively simple – it is widely used in scientific circles – it could lead to destabilizing effects for the modified organism. In contrast with what is generally sustained by the GMOs' supporters, the introduction of genes in fact triggers profound changes within the plant or animal species. The latter could react to the modification with unpredictable effects.
According to Gianni Tamino, biology professor at the University of Padua-Italy, through the random insertion of genes into the organism, transgenesis can alter the functioning of the genes that are already embedded within the living organism. The genes, explains the scholar, are interrelated with each other in a complex way, and when a new one is introduced, the functioning of all genes could result in being unsettled.
Referring to an important report released by the British General Medical Council in the first half of 2003, Michael Meacher, Great Britain's minister for the environment from 1997 to the beginning of 2003, asserts that such genetic material could activate silent genes present in the organism whose effects are unknown or, at worst, could even be toxic.
Potatoes and Lab Rats
With the benefit of hindsight, that is what may have occurred in Arpad Pusztai's highly controversial study. The well-known Hungarian biologist and his staff administered genetically engineered potatoes to lab rats. In the genetic makeup of the potatoes a gene was inserted that was destined to produce an insecticide. This resulted in the potatoes' DNA experiencing a deep transformation. At the same time, a second group of rats was fed with regular potatoes in which the same insecticide was mixed. In this case, without genetic manipulation.
The group fed with GE potatoes was found to have abnormalities on parts of the stomach as well as in the small and large intestine. In the second group, none whatsoever. It was not the insecticide that caused these abnormalities, but the process itself to modify the organism's genetic makeup – in short, the transgenesis – whose effect consisted of modifying the regular functioning of the hereditary makeup of the potatoes, which in turn brought up a toxic reaction for the rats.
Although Pusztai's experiment was strongly criticized by both biotech industry and a component of the British scientific establishment (mainly by scientists who had strong stakes in the biotech field), it identified the GMOs' problem very well. At issue is not the transgenesis per se, but the organism's reaction to it. How will the existing genes react to the newly inserted gene? Will there be any consequences for the organism? If yes, what kind of impact will result?
In addition to the possible afore-mentioned risks, there are two that deserve the greatest scrutiny. The first one consists of the possibility that the consumption of genetically modified foodstuffs by humans may transmit ever-growing resistances towards antibiotics. Aside from containing genes for the resistance against diseases or insecticides, GMOs are simultaneously designed with special genetic sequences to resist antibiotics.
These sequences, called "markers," are commonly utilized in labs because they enable the process of verifying whether the first steps of transgenesis have correctly taken place. The danger for humans is that once the GE foodstuff is ingested, its DNA which is highly unstable because of the modification process, could be fragmented. Therefore, as shown in several studies, resistances to antibiotics that are embedded within GMOs could easily be transferred to the bacteria that live in the mouth and in the intestinal flora. The pathogenic bacteria that, during an illness, colonize our mucous membranes, could acquire the capability to resist antibiotics.
As a result, in order to defeat these germs, it would be necessary to opt for different or even more powerful antibiotics, with the possibility of increased side effects. Because of this, the European Union has adopted a directive on the release of GMOs into the environment, in which the trade of GE foodstuffs containing resistances to antibiotics must come to a total end by late 2008.
New Viruses
The second risk concerns the possibility of the emergence of new viruses. Usually, in order to genetically modify an organism, the insertion of the new gene must be accompanied with other genetic material, called promoters. The promoter's goal is to guide the new gene towards the desired effect. The added hereditary sequence often comes from viruses. The most common example is the 35S promoter deriving from a mosaic virus that hits cauliflowers. Such sequence is introduced into a few GE plants. As is often the case with GMOs, it can be rejected and transferred to other places of the genome, other cells or even other organisms. In the specific case of the 35S promoter – but it could be valid for other genetic material – it could activate genetic sequences containing latent viruses of the genome.
Due to the instability generated through the insertion of the gene and the hereditary material, these viruses may move into other living beings, including humans, and evolve into dangerous forms for them. The avian influence is emblematic of the strong likelihood of the appearance of the new lethal viruses that could spread among organisms from different species. With the cultivation of GE plants and the breeding of GE animals, this possibility is even more likely.
To date, in-depth studies showing the possible consequences of foodstuffs consumption for humans have never been carried out. The only effects discovered so far consist of allergies and, more ominously, a mysterious disease that, at the end of the 1980s, resulted in the death of 37 people, and paralyzed more than a thousand individuals in the United States. The L-Tryptophane, a GE food supplement, was identified as the cause.
The biotech multinationals that operate in the agro-food sector have always refused to undertake comprehensive examinations investigating such risks and, through political lobbying, have ensured lenient controls from public agencies. During a conference in Geneva in June 2001, Jeoffrey Kelley, director of external affairs for Europe for Dupont, an American corporation active in the biotech sector, explained the reason companies cannot perform such studies to a student audience from the University of Southern California, "If the multinationals that have invested a lot money, such as the Monsanto corporation, had to wait for the results of these studies before introducing their products into the market, they would be destined to bankruptcy."
Transgenic Agriculture
If the presence of health risks is still not clear for the genetically modified organisms that are currently grown, one could conclude they are more likely with the new generations of GE plants built to produce medicals and industrial chemicals. As recently indicated in the report released by the Union of Concerned Scientists, a group that counts high-profile American scientists among its members, such organisms cultivated in the open could in fact contaminate agricultural fields with serious dangers for human health.
To date, in regard to health risks, there are too many elements that suggest we should be very cautious towards transgenic agriculture and the breeding of GE animals. Such cautiousness seems even more justified by observing the large increase in the number of diseases linked to food consumption, which have appeared in the United States since the introduction of GE foodstuffs.
The U.S. government's Center for Diseases Control believes that food-derived illnesses have almost doubled in the last seven years. This does not mean that the increase is to be attributed to the GE foodstuffs, but by the same token, it cannot be excluded. The outbreak of Mad Cow disease, which is recognized as the cause of a new variation of the Creutzfeldt-Jakob illness, should prompt us to pay serious attention to the possibility of such risks.
The GMO critics of today are faced with the same backlash as those who warned about the possible consequences derived from the usage of animal feed were subjected to in Europe a few years ago. The pattern of pinning "anti-science" labels on critics and subsequent allegations of incompetence are as evident today as they were back then. However, with hindsight we all know now that their warnings have proven to be well-founded.
While for human health the consequences still remain unclear, it is a different story for the environment. Studies that have been undertaken so far do not leave room for doubts: transgenic agriculture and the breeding of GE animals have harmful repercussions for nature. In particular, the effects are great for biodiversity.
Biodiversity is a cornerstone of biology, and holds a twofold meaning. First, it refers to the variety of individuals present within a single species: the more diversified these are, the higher the species' likelihood to survive adverse situations such as epidemics or climate changes. If a species is made up of homogenous individuals in terms of the genetic makeup, it probably will be destined to extinction.
On the contrary, if its members are heterogeneous, it is possible that a few of them, endowed with particular hereditary traits, will be able to overcome the epidemics or the specific climate condition unharmed. Secondly – and in a broader sense – the biological diversity alludes to the multiplicity of species that inhabit a specific ecosystem. The more the environment is populated by numerous species, the better its state of health. A habitat that shelters a lot of species – therefore ruled by lots of interactions – results into a more balanced condition. With the genetically modified organisms, however, biodiversity, which is already threatened by other human activities, is seriously endangered.
Because of these organisms' aggressive nature, there is a high probability for genetic pollution to occur. Through pollen transported by bugs and wind even for long distances, the genetically modified plants are able to contaminate other vegetable species, including wild ones. Particular genetic make-ups of plants, whose process of evolution can have taken place over thousands of years, risk getting lost because of the cross-pollination with the transgenic organisms. The result of this is a reduction in biodiversity, which explains what could have happened in the Mexican state of Oaxaca.
Contaminated Corn
In the winter of 2001, Ignacio Chapela and David Quist, two researchers from UC Berkeley, discovered contaminations within the cornfields of this Mexican state. While the results of their research are still in dispute, the contaminations could be attributed to the crops imported from the United States where, in contrast with the Latin American country, GMOs' cultivations are authorized. The American grains could have ended up in a few Oaxacan fields by mistake, and, through cross-pollination, could have polluted the surrounding crops.
If the two scientists' observations turn out to be accurate, humanity should indeed be concerned.
As explained by Mark Shapiro in his article "Sowing Disaster", Oaxaca, thanks to its biodiversity, is very important for the world's food security. Everytime the crops from a specific region in the world are hit by disease, parasites or various environmental phenomena, this area of Mexico becomes the destination of choice for international agronomists. Due to the numerous varieties of corn that grow there, scientists can find the solution to their problems. Through the taking of samples of the most suited plants, they are generally able to find remedies to the adversities that hit crops worldwide.
Preserving Oaxaca's biological diversity is therefore essential to face the unexpected events that target an important human source of supplies. If the two researchers' discovery were proven to be true – and this is not unlikely given that many contaminations have already occurred around the world – it would not be an exaggeration to conclude that, with the corn's contaminations of this Mexican state, the global food security has suffered a serious blow.
40 Generations of Fish
The transgenic animals also have grave consequences for the environment. The new organisms are so pervasive that do not give the various ecosystems present on the planet the necessary time to adapt to the newly introduced species.
A group of scientists from Purdue University discovered that GE fish could bring entire populations of wild fish to extinction. In only 40 generations, a relatively short time in evolution, the modified fish win the competition with their wild counterparts thanks to their bigger size, which enables them to hunt more food and pair up more easily. The researchers' study also shows that, in order to cause the disappearance of a 60,000 fish stock, it is enough that 60 modified exemplars escape from a hatchery. That such an escape is possible is also confirmed by the report released by the National Council for Research of the American Academy of Sciences in January 2004. The report states that it is difficult if not impossible to prevent the escape of GE animals from the breeding sites and, more generally, the overall spreading of GE organisms.
GMOs also threaten the environment in another way. Contrary to the view promoted by the supporters of the new technology, in general, consumption of pesticides has actually increased with the genetically modified organisms' push.
This is what emerges from the study by Charles Benbrook, head of the Northwest Science and Environment Policy Center in the United States. Through the data of the U.S. Department of Agriculture, the research examined the impacts of transgenic agriculture in the United States from 1996 to 2003. The study concluded that despite the fact consumption of pesticides had indeed been reduced during the first years of GMOs' cultivations, it has significantly increased in the following years, to the point that today the amount of pesticides sprayed on most transgenic crops in the United States is higher than the doses used in the conventional agriculture.
The only exceptions are the Bacillus Thuringiensis (Bt)-Maize and Bacillus Thuringiensis (Bt)-Cotton for which there is a limited decrease of the insecticides utilized. In the future, as we shall observe, this slight decline, however, is most likely to reverse. But why then, except for the two afore-mentioned species, has there been an overall increase in the consumption of pesticides for the genetically modified organisms in the United States?
The reason lies in the nature of the most common variety of GMOs, the herbicide-tolerant plants. These, together with the Bt-plants, represent the essence of transgenic agriculture.
Thanks to the capability to resist herbicides, the herbicide-tolerant plants can be targeted with weedkillers without sharing the destiny of the infesting weeds that in most cases are eliminated. Through the pollen, however, such GE plants can fertilize other vegetable species in the nearby areas, with the result of transmitting to them part of the resistance to herbicides. This phenomenon, defined as hybridization, frequently takes place in the transgenic cultivations, and represents a serious problem. With the fields now free from weeds, in fact, these vegetable species are able to spread without any trouble, and threaten the cultivation of GMOs. At such point, given the resistance conferred on these weeds, the amount of the herbicides previously administered are no longer effective, and it is necessary to resort to stronger doses.
Pesticides Consumption
In the future, the increase in the consumption of pesticides could even expand. According to several biologists, it is highly probable that there will be a rise in pesticides used for the second variety of GMOs, the Bt-plants. This increase is also caused by the characteristics of the modified organism.
In the genetic makeup of the latter variety, which includes Bt-corn and Bt-soya, a gene is integrated that enables the modified plants to continuously produce a toxin from a bacterium, the Bacillus thuringiensis (Bt). This toxin then acts as an insecticide. According to Gianni Tamino of Padua University, on the one hand, the ongoing Bt-production certainly permits the elimination of many parasites, but, on the other, within a few years it does not do anything but strengthen the insects.
"In a four-five years' time, in the areas where these cultivations are carried out, by reproducing themselves ... these insects will become more resistant and aggressive. As a result, it will no longer be possible to utilize that kind of toxin, and it will be indispensable to use larger quantities of insecticides."
What has been described by Professor Tamino already happened in Bt-cotton cultivations in three major states of Northern India Madhya Pradesh, Maharashstra and Gujarat. There, farmers who heavily invested in the Bt-technology, saw their Bt-cotton fields being completely wiped out by the emergence of new and more resistant pests. Because the cultivators had devoted all their funds to the purchase of the Bt-cotton seeds, they could not resort to stronger insecticides that might have avoided the destruction of their plantations.
The high consumption of pesticides which, as observed, generally accompanies transgenic agriculture, and which in the future could spread to all cultivations of Bt-plants, is not a fact limited to the United States alone. In Great Britain, an in-depth study commissioned by the British government and undertaken under the name Farm Scale Evaluations, examined the possible consequences of GMO cultivations for the U.K.'s ecosystem. The scientists responsible for the experimentations agreed that the genetically modified organisms harm the wild fauna and flora because of the more widespread consumption of pesticides.
During a three-year period, in more than 200 sites across England and Scotland, three GE plants – GM beet, spring oilseed rape and maize – were compared to their conventional counterparts. With the only exception of GE maize, the other two modified varieties had serious repercussions on wild animal and vegetable species. The positive result of GE maize is however to be linked to the application of atrazine on the traditional maize. Atrazine is an insecticide that has been banned by several European Union countries because of its high toxicity. Soon it may also be withdrawn from the British market for the same reason. A few scientists believe that if a different product had to be sprayed on the conventional maize, the transgenic variety would have most likely resulted in the same negative impact of the other two species.
The result of the British study is another confirmation about the harmful effects that GMOs have for the environment. In the future, other consequences could be added to the ones that are already known.
GMOs' Irreversible Nature
To make the extent of the danger of the new technology to the environment more apparent, there are two additional elements to consider. These are the extraordinary capability of proliferation embedded in GMOs and, more importantly, their irreversible nature.
In addition to spreading through reproduction in vegetables and animals, the new organisms could also expand themselves through a horizontal transfer of genes. The hereditary material inserted into the organism's DNA and expelled by it because of its high instability, can be assimilated by other organisms. In the GE plants, the rejected genetic material is absorbed by soil bacteria that in turn are able to transmit it to other organisms such as vegetables and animals. Hence, the possibility of pollution that surrounds the new technology is very high.
Furthermore, the irreversible nature of GMOs makes the issue of genetic manipulation in agriculture and breeding even more serious. Unlike traditional sources of pollution such as the one bound to fossil-fuel consumption, the situation concerning GMOs is totally different. Once the genetically modified organisms are released into the environment, they trigger reactions from which there is no longer a point of return.
Does the fact that a few countries, including the United States, Argentina and Canada, have embraced transgenic agriculture mean that the battle against GMOs is lost? Absolutely not. The vast majority of countries have so far refused the transgenesis in agriculture and breeding. And even where it is authorized, there are many spaces that are still uncontaminated and that ought to be defended.
An analysis of the dangers of genetically modified organisms would not be complete without a discussion of the socio-economic risks and the issue related to the fight against world hunger. That will be the topic of a future article. For now let it be said that, contrary to what GMOs' supporters maintain, genetically modified organisms are everything but the solution to world hunger.
Christian Zarro is a candidate for a MSc. in media and communications at the London School of Economics. Igor Cima graduated from the University of Bern-Switzerland with a Ph.D. in immunology.