quinta-feira, 12 de abril de 2012

What is a LMO/GMO “not likely to have adverse effects on the conservation and sustainable use of biological diversity, taking also into account risks to human health”?

Suggested complementary reading: http://genpeace.blogspot.com.br/2012/06/comments-on-ahtegs-guidance-on-risk.html

How to produce a meaningful list of safe GM (transgenic) plants and microorganisms

The CBD Secretariat requested in one of the provisions of the medium-term program of work, i.e., decision BS-I/12 paragraph 7 (a) (i), that the Cartagena Protocol Parties should suggest a list of LMOs not likely to have adverse effects on the conservation and sustainable use of biological diversity, taking also into account risks to human health. Are the LMOs currently in the market causing any adverse effect, beyond those already observed due to the use of the parental, no GM organism?

The answer is clear: no.

Before commercial release all LMOs were detailed evaluated on their potential risks for the environment and for animal and human health and all of them were considered to be as safe as their non GM counterpart. Obviously, the risk assessment was done for each country interested in using it (either as a crop or as an industrial LMO). As far as the food safety is concerned, conclusions from one national authority can be safely taken worldwide. But environments change significantly from place to place. Can we confidently extend environment risk assessment conclusions from one country to another?

The answer is: in most cases, yes, we can.

Why? Because threats are much more dependent on LMO behavior, which is usually very similar and often identical to its non GM parental line, than on gene trait.

As an example, a Bt corn behaves just like a normal corn: it is not invasive, it is highly dependent on human beings for its survival, it continues to depend on wind to cross and has all other phenotypic characteristics of a regular corn. However, it is resistant to certain insects. Therefore, the threat, if any, will be related to this trait (insect resistance) and its passage to other plants by cross pollination. Wild plants able to cross with the commercial corn can receive the pollen and, in very special circumstances, can introgress the new gene, but this last case will depend on the existence of a strong selective pressure allowing not only gene selection, but also strong enough as to overcome hybrid disadvantages in natural (wild) conditions. Mexico has now a long experience with Bt corn and there is very little, almost anedoctal evidence of any impact in wild corn populations. A last safety issue is the impact on non-target organisms (NTOs) but, as far as we know, the Bt corn has in real life no visible impact on populations of non-target organisms (even if it could eventually kill some NTOs in specific, highly artificial lab conditions).

However, a single example is no reason to believe that general guidelines to indicate a worldwide safety do exist. Can we envisage such guidelines?

The answer is: yes.

To ease our task, let us divide the LMOs in two groups: those expressing a novel protein (or a couple of them) and those that do not express novel proteins (although they display novel traits).

I)     When novel proteins are expressed
1)        Plants
a)      For the food risk assessment, we must assume that once a national authority considered a LMO safe, there is no reason to imagine that it would represent any threat anywhere in the world, as human beings are quite the same as far as physiology and immunology are concerned. Some protein characteristics are usually investigated (thermostability, digestibility, lack of allergenic epitopes, etc.), following internationally accepted guidelines. A history of safe use also supports a risk assessment conclusion and is always welcome.
b)      For the environment risk assessment, as stated above, we assume that the novel trait is the unique determinant of changes (if any) in the organism safety profile. All marketed LMOs up to know were selected from hundreds of initial transformed candidates because of their behavior, i.e., they looked exactly like their non-transformed parental, except for the new trait. Therefore, we can list the paradigmatic characteristics of a safe LMO/GMO, be it a plant, a microorganism or whatever other living being:
·         It must have a behavior identical to the non-GM parental, except for the new trait (this is usually the case and conclusions can be extended worldwide)
·         The new trait shouldn´t give to any LMO´s wild relative such a competitive advantage as to risk the normal population density or distribution of this relative (a very strongly selective pressure must exist in order to ensure gene introgression; the conclusions can be usually extended worldwide, especially when observations in centers of origin indicated no damage).

2)        Microorganisms
a)      For the food risk assessment, considerations are the same as above.
b)      For the environment risk assessment, the guidelines are also similar as those discussed for plants:
·         The GM microorganisms should not advantageously compete with wild populations of non GM closely related organisms. This is usually the case, as GM microorganisms are extensively genetically manipulated to reduce their ability to grow in non assisted conditions.
·         The GM microorganisms should not produce toxins (except is this is the objective of the transformation).
·         Preferentially they should be unable to conjugate or somehow transfer their new gene construction.

3)      Animals
There is usually a sexual barrier between different animal species. Even so, sometimes fertile hybrids can be produced in special conditions. Therefore, essentially the same considerations listed for plants or microorganisms apply also for GM animals. Since animals can in some cases quickly spread in a region, it is also important to consider the eventual competition between GM and non-GM strains. If the region is endemic for the species under consideration, special restrictions may be needed.

If these conditions are met, it is warranted to conclude that once they have been considered safe in a country, they will be safe in any other part of the world.

II)    When novel proteins are NOT expressed

For the food risk assessment the same considerations above mentioned for plants do apply, but the lack of any new protein usually will ease the assessor´s task. For environment risk assessment, some of the above questions are still valid and the general approach is again the same.

Now let us look at the list of commercially released LMOs:
• alfalfa – herbicide tolerance
• Bean – virus resistance
• Chicory – pollen sterility (for breeding hybrid varieties)
• Argentine canola –  altered oil profile, herbicide tolerance, pollen sterility
• Polish canola – altered oil profile, herbicide tolerance, pollen sterility
• Cotton – insect resistance, herbicide tolerance
• Carnation – altered flower color
may hybridize with local Dianthus spp. and hybrids invasive
End-point: unlikely
Fact: no such occurrence over ten years
• Flax, Linseed – herbicide tolerance
• Maize – insect resistance, herbicide resistance, drought tolerance, pollen sterility, heat-stable alpha-amylase for ethanol production; phytase
• Papaya – virus resistance
• Plum – virus resistance
• Poplar – insect resistance
• Potato – virus resistance, insect resistance

Except for alfalfa which, in certain conditions may be a weed, all other plants are very unlikely to be invasive: they do not display the necessary characteristics. Moreover, the new GM traits by themselves will not change the plant behavior, and this is also true for alfalfa: the GM variety is by no means more invasive than its no GM counterparts.

Carnation is not invasive, but it could cross with other invasive wild relatives. This, however, was never observed. Beans did not reached the market yet, but they are a priori safe, as no new proteins are expressed and the plant has no weed characteristics and usually do not cross with other plants. Finally, after many years of use in different countries around the world, no changes in weediness were ever been observed for all plants listed above. Therefore, we may disregard invasiveness (weediness) as a real threat.

Crossing with wild relatives may vary from place to place, but there are no reasons to believe introgression could occur, as the selective pressure is almost certainly absent.

All GM plants up to now have all the expected phenotype of non GM plants, except for the transgene expression. And, after many years of extensive use, none of them were reported as causing any type of harm to the environment or to animal or human health. We are then forced to conclude that these LMOs are generally safe for the environment and for humans and animals.

Many GM microorganisms have also been developed and most of them are cultivated in containment. Those which are deliberated introduced in the environment invariably fulfill the requirements listed above. We therefore also conclude that these GM microorganisms are generally safe.

A similar approach can be used to evaluate the safety of other LMOs, including viruses. As all of them are marketed only after an extensive risk assessment, and are considered as safe as their no GM counterparts in the countries were they have been evaluated, we may advance that all GMOs in the market will be, sooner or later, considered “not likely to have adverse effects on the conservation and sustainable use of biological diversity, taking also into account risks to human health”

Paulo Paes de Andrade
Federal University of Pernambuco

Um comentário:

  1. Dr. Paulo Paes clearly stated what science and decades of use confirmed. All GMOs so far released in the environment are safe on all accounts required. They are organic modifications of a living creature with the purpose of obtaining a new useful variety better for man, animals, environment and economy. They are "green" products of biotechnology, the fulfilled dream of Rachel Carson who wanted to reduce (or even abolish) the use o chemicals in agriculture. Their creation means an increase in that particular category of biodiversity that is useful to mankind: our pet plants, that we started to tame over 10,000 years ago. There is no reason for man to avoid emulate mother nature, always prodigal in moving genes around species, genera and even phila as reported in the current literature. Our own, nucleated eukaryotic cells of animals and plants arose by a bold and, for the anti-biotech purists of today, totally "artificial" move: one cell "swallowed" another. The canibalized, one derived from a bacteria, ended up as the important organelle known as mitochondria. Cells that engulfed a photosynthetic bacteria ended up with an organelle known as chloroplast, so the plant cell can harvest energy from sunlight. Can anyone devise in our labs a bolder experiment? Without it the Earth would be clear of green plants and animals. The fantastic biodiversity that surrounds us in animals and even more so in microrganisms (they are around for over 3.6 billion years), is a toolbox of gene products like none other. Man should, for the benefit of animals and environment, access this treasure and use the potential of these genes. We now have the technology to do so, imitating nature. Most important, the modifications are perfectly traceable, we are able to detect the presence of the new gene with enormous sensitivity. So we have moved from improving crops by blind heavy radiation or chemical mutagenesis, leaving the plant with dozens of unknown mutations (and commercialized over 2,000 such varieties) that may spread around silently, to a precise manipulation that controls almost all relevant aspects of the process.