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published on 3 November 2006 in life

GMO

Genetically modified organisms
Two months ago some lots of rice reached Europe from the United States by sea, and were finally blocked in the Rotterdam harbour, in Holland. Despite the documentation certified that the cargo was GMO-free (GMOs are also called “transgenic organisms”), the analyses made by European laboratories gave opposite results, with the outcome that the control institutions decreed that the goods could not continue the journey to the EU countries since they were not in line with the laws regarding transgenic products. Beyond the many political and economic discussions fuelled by the event, it can be useful to understand the reasons why there is a system of surveillance on genetically modified foodstuffs regulated by precise norms that safeguard the environment and consumers’ health (in this special we discuss the first aspect). In other terms: why has the diffusion in the environment of transgenic organisms generated so much interest?
Some preliminary information
It is useful to clarify from the beginning that in the majority of cases where the environmental risk of GMOs is under scrutiny, in fact the discourse is limited to plants. Indeed, although it is true that with genetic engineering techniques it is possible to intervene virtually on every organism (from micro-organisms to animals), it is also true that the great part of the interest that has been generated around GMOs concentrates on plant species of agro alimentary relevance, such as soy (Glycine max), maize (Zea mays), rape (Brassica napus), rice (Oryza sativa), wheat (Triticum aestivum), beetroot (Beta vulgaris), turnip (Brassica rapa), tomato (Lycopersicon esculentum) and other, not always strictly alimentary species, such as for example tobacco (Nicotiana tabacum). It should also be noted that not all the genetically modified variants of these plants have been authorised in Europe.
Another very important aspect to clarify as a preliminary is that genetically modified plants are obtained with laboratory techniques that are very different from the selection and hybridisation techniques of traditional genetic amelioration. With these “genetic engineering” techniques, that exploit the recombinant properties of DNA, in fact, genes foreign to the original complement can be inserted in the plants’ genome, as it often happens, from organisms belonging to other biological realms. Thanks to these genes – called “transgenes” by many scientists, because they are able to fix themselves overstepping the barrier between species – plants can express physical and chemical characteristics that would otherwise be difficult to express, such as the synthesis of biological pesticides to kill agricultural pests without the use of disinfestations techniques by farmers. In any case, characteristics that are believed to increase croppers’ harvest.
The realm of uncertainty
The risk associated with genetically modified plants has been, and still is, at the centre of a lively debate between scientists and other operators in the agro alimentary sector. To be able to understand the reasons behind this debate and, more generally, to understand the distrust that has been shown at the European level (but not only there) in regard to GMOs, it is useful  to make a small incursion in the “realm” of risk. According to a very simple definition,  risk  is nothing else but a useful concept to describe the state of uncertainty of our knowledge in respect to possible events. If you think about it, it is a concept that we all use constantly, even in everyday life, for example when we take the umbrella even when it’s not raining. Normally, in fact, before we go out we base ourselves on a “span” evaluation of external meteorological conditions (will it rain? – won’t it rain?) to make very simple decisions. When our instinct suggests that “the risk” of returning home wet through is imminent, that is very probable, then we take an umbrella or some other protection that will ensure that we stay dry even in the case of rain. By making that choice, moreover, we operate something similar to an act of prevention, i.e. we accept the hassle of an extra object to carry in our hand (the umbrella) assuming that this choice can avoid us greater hassles, such as returning home wet through and perhaps catching a cold.

Prevention and precaution
With GMOs, but also with other impact factors, a concrete prevention measure  comparable to the one described above has not yet been designed, because true preventive action is based on two very important elements of initial information:

  • the knowledge of the type of risk to which one is exposed,
  • the knowledge of the probability that the risk might become a fact.

Returning to the above example, we know well that the risk of going out without an umbrella is to get wet if it rains (typology); moreover, we know that, if there are very low clouds in the sky and no wind to blow them away, the possibility of rain could become reality (probability). Even if it’s not a proper calculated risk, we just pretend that it is, and act accordingly.
Well, with GMOs these two pieces of information are not very clear, first of all because, since they differ from one another, GMOs are potentially responsible for very diverse risks, both for typology and seriousness; secondly because, being very new impact factors, it has not yet been possible to quantify the probability with which they can damage the environment (and human health). What we know is that if GMO risks are founded – as has been already signalled by the first experimental results – the damages linked to their release in the environment can be extremely severe: think for example about the strong impact that they can exercise on reduction of biodiversity due to genetic pollution(see below).
While dealing with these organisms (or with other little known impact factors), then a new notion of risk must be coined: a notion with more theoretical than practical value, and that as such implies actions of precaution rather than true prevention.
The notion of precaution applied to environmental risk says that, without consolidated knowledge on the possibility of damage to the environment of a new activity, or a new technology, this gap should not be used to authorise that activity or technology, but rather the decision should be suspended until more exhaustive knowledge is available. Put simply, many scientists believe that there is a lack of precise knowledge about the possible damages (and the probability that these might occur) deriving from the diffusion in the environment of GMOs. Current scientific knowledge allows to hypothesize that the damage to the ecosystem could be serious and irreversible and therefore, while we wait for more reliable data, inputting them in the environment through open field cultivations could be a mistake.
Having said this, the environmental risk that derives from the cultivation of genetically modified plants can be classified – on the basis of the organisms that are directly affected by them – in the following terms.

Vegetable organisms
Pollution from vertical genetic flux (VGF)

It is in substance the diffusion of a GM vegetable species’ (or population’s) transgenes within the genetic pool of another sexually compatible vegetable species. This means that through sexual reproduction the characters of a transgenic cultivation can be transmitted to a non-transgenic cultivation, or any other plant that has reproductive affinities with the first one. The VGF is linked to the transfer of pollens from transgenic cultivations to conventional ones and to wild plants, while the risk regards the possibility that transgenes might be propagated through it thanks to the normal sexual reproduction processes, with unpredictable ecological effects. As for this typology of risk, cases of genetic pollution produced by GM rape and beetroot cultivations are already known.
Pollution from the dispersion of transgenic seeds (DTS)
This refers to the possibility that GM seeds could spread themselves engendering transgenic plants in environments where these are not wanted (for example in organic cultivations) or can result damaging (natural ecosystems). In this latter risk type the possibility is also included that transgenic seeds give way to plants with characteristics that enhance their invasiveness or reinforce their reproductive success (fitness) at the expense of spontaneous plants, with serious imbalances at the expense of the biological communities.

Animal organisms
Reduction of non-target animal populations (RAP)

This entry falls into the typical risk associated to plants genetically modified to counter the damages caused by animals that infest agricultural cultivations. It has been demonstrated that the toxic substances produced by these plants are in fact dangerous not only for the parasites (target animals), but also for other animals (non-target animals), even for species that carry out a useful role in agrarian ecosystems (pollination, capture of parasites, etc.).
Selection of resistant parasite populations (SRP)
It is an often neglected aspect but it can be the root of many problems for farmers in the management of their fields. In fact GM cultivations for the production of pesticide substances, apart from killing non-target animals, as a collateral effect can also select strains of resistant target animals, that are not affected by those substances.
The result is an increase of the parasite population (usually insects) that can become very difficult to stop, without recurring to interventions based on the application of large quantities of pesticides, that are notoriously toxic for man as well.

Micro-organisms
Pollution from horizontal genetic flux (HGF)

This form of genetic pollution is essentially linked to the possibility that transgenic DNA fragments can transfer themselves, through simple DNA recombination, from GM plants’ genome to micro-organisms’ genome, such as bacteria or viruses (and from here to other organisms). Through this process, moreover, it is always possible that DNA segments that create resistance to antibiotics are transferred as well, that is the transgenes used in laboratory as “markers” to highlight that genetic manipulation of primary vegetable cells has taken place (transformation). In this regard, the possibility has been described that resistance to antibiotics will be translated from transgenic plants to other organisms, such as for example pathogenic bacteria that are dangerous for humans (or other organisms), with, once again, unpredictable effects.

Written by Carlo Modonesi

With the sponsorship of the Italian Ministry of Education, Universities and Research
 
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