Topic in Focus
How Safe is Green Genetic Engineering for the Environment and Human Health?
Photo: IPK/ Andreas Bähring
Plants bred with the help of green genetic engineering must not pose any risks to the environment out in the fields and must be safe for human consumption. This is what the European regulations stipulate. For a science-based safety assessment, it all depends on the product. If the genetic modification can occur in the same way in nature or through conventional breeding, novel risks are not to be expected.
Decades of experience with products of green genetic engineering have been accumulated so far. Although the precise procedures of genome editing, including the CRISPR/Cas genetic scissors, are new, conventional genetic engineering methods, which also involve interventions in the genetic material, have been used in agriculture for a long time. The first genetically modified crops appeared on the market in the mid-1990s. The first generation methods primarily produced transgenic plants – i.e. those to which the gene of an unrelated species was transferred, for example, a bacterial gene for herbicide tolerance. The introduction of green genetic engineering was accompanied by a public discourse on possible risks. In Europe, the community legislator established restrictive legal regulations with time-consuming and costly market approval procedures.
At the same time, genetically modified plants were investigated for their safety – i.e. possible adverse effects on the environment and human health. Numerous safety studies conclude that genetically modified plants per se do not pose a higher risk than plants produced by conventional breeding technologies.
Experiences with conventional genetic engineering
The era of green genetic engineering began in the USA in 1994 with the approval of the so-called anti-mush tomato, which was developed through genetic engineering. Two years later, farmers in the USA sowed genetically modified crops on a large scale for the first time: new varieties of maize and soybeans. Since then, the acreage for cultivation of genetically modified crops has continued to expand worldwide. In 2019, a total of 190 million hectares were planted with genetically modified soybeans, maize, cotton and rapeseed.
Products of conventional genetic engineering are used mainly by farmers in the USA, Brazil, Argentina, Canada and India. In Europe, these products have little significance. The only product approved for cultivation in the EU is the maize MON810, which is resistant to plant feeding insects. In 2020, it was only cultivated in Spain and Portugal. In Germany, the cultivation of this maize variety has been banned since 2009.
The application of genetic engineering has been accompanied by biosafety research from the very beginning, also in Germany. Initially, the focus was on procedures with which additional genes could be introduced into the genome. In the case of conventional genetic engineering projects on plants, these have so far mainly been genome sequences from other species. A typical example is the transfer of bacterial genes that impart a particular property, such as an insecticidal effect. Plants into which a gene from another species has been inserted are called transgenic plants.
Since the end of the 1980s, the German Federal Ministry of Education and Research (BMBF) has funded several projects focusing, among other things, on possible environmental effects. Researchers have been particularly concerned with Bt maize, which contains a gene that is found when the soil bacteria Bacillus thuringiensis are present. It causes the production of the protein Bt, which annihilates certain insect pests after ingestion. Bt maize thus repels plant feeding insects such as the European corn borer. The projects investigated whether maize Bt proteins could be harmful to other living organisms, for example, bees, butterflies or soil organisms. Such effects were not found. On the contrary, it was shown that conventional maize cultivation using chemicals against the European corn borer has more severe ecological consequences.
A review published by the BMBF in 2014 showed that after 25 years of biosafety research on genetically modified plants, no indications of risks specifically attributable to genetic engineering or correspondingly modified plants could be found. In 2010, the Commission of the European Union (EU) had already drawn a similar conclusion after more than 25 years of biosafety research on transgenic plants. The conclusion drawn from more than 130 research projects involving around 500 independent groups of researchers is that biotechnology and especially genetically modified plants are per se not more risky than conventional plant breeding.
Scientists from the University of Perugia/Italy also published a particularly comprehensive evaluation of almost 1,800 studies and reports in 2014. The meta-analysis concludes that the scientific studies conducted so far have not identified any significant hazards associated with the use of genetically modified crops. From a scientific point of view, a blanket rejection of genetically modified crops for safety reasons is untenable.
“The discussion about risks basically revolves around the two major issues of health and the environment. As far as health is concerned, it can be said that transgenic plants have been eaten worldwide for more than 25 years without any human being ever being harmed. And more than ten thousand scientific studies have found no evidence of health risks. A few studies have claimed so, but these studies have subsequently been found to be grossly flawed and unreproducible. The situation is very similar in the environmental field. Transgenic plants have been grown commercially for over 25 years. With the cultivation area increasing every year, they meanwhile cover about 15 per cent of the world’s agricultural land. Also, extensive safety research has been carried out for more than 30 years, and here too it can be said that in more than 10,000 scientific studies no indications of adverse environmental effects have been found.”
Photo: MPI-MP
Targeted mutagenesis through genome editing
Long-term experience is not yet available for new genetic techniques such as CRISPR/Cas. At the same time, however, there is no scientific evidence that targeted genome editing methods are associated with specific risks. This is emphasised by the German National Academy of Sciences Leopoldina, the German Research Foundation (DFG) and the Union of the German Academies of Sciences and Humanities in their joint statement from 2019 on the regulation of genome edited plants. They point to the widespread consensus in the life sciences that genome editing methods in which only individual genes are deactivated or modified are equivalent to the products of traditional breeding.
For a European Commission study on new genomic techniques published in spring 2021, the European Food Safety Authority (EFSA), which is responsible for food safety in the EU, prepared an overview regarding the scientific risk assessment of their application. It also concludes that there are no novel risks associated with the use of targeted mutagenesis through genome editing compared with traditional breeding methods.
Mutagenesis generally refers to the creation of mutations – i.e. changes in the genome. This was already possible before the advent of genetic engineering. Traditional mutagenesis, as has been practised in plant breeding since the 1960s, is random and takes place using chemical substances or ionising radiation with mutagenic properties. The location in the genome where changes take place cannot be controlled in this process but only subsequently verified. In addition, numerous off-target mutations occur frequently. Targeted mutagenesis was first made possible through the development of genetic engineering methods in the 1980s, and genome editing has recently improved precision considerably. With methods such as the genetic scissors CRISPR/Cas, almost any location in the genome can be precisely modified. Off-target mutations are significantly less common with targeted mutagenesis.
In principle, cisgenesis and transgenesis should also be assessed differently. The term cisgenesis refers to applications in which plant genes originating either from the host species itself or from a close relative are transfered through genetic engineering. An example of cisgenic plants are potatoes, which become resistant to late blight by transferring a gene from wild potatoes. In contrast, transgenic plants contain genetic material of another species. A well-known example is MON810, a maize variety produced with conventional genetic engineering. A gene from the soil bacteria Bacillus thuringiensis was inserted into its genome for pest resistance.
When it comes to safety, the decisive factor is which properties of the plant have been altered with the gene scissors. If the resulting product could also have been created through traditional breeding or natural mutation, the situation is different from a case where genes from other species are inserted. This is why many experts advocate a regulation referring to the genome-edited product rather than to the underlying procedure.
As for the new breeding methods and their products, the fundamental question arises as to whether they should continue to be regulated restrictively across the board. The statement by the Leopoldina, the DFG and the Union of the German Academies of Sciences and Humanities also addresses this aspect. Considering the precautionary principle is particularly important when there is still a great deal of scientific uncertainty. At the same time, the scientists point out that it does not apply in the residual risk area – i.e. when there are uncertainties beyond the ‘threshold of practical reason’ and risks appear practically impossible according to the state of the art in science and technology. And in this sense, there is no specific new precautionary reason regarding the new methods of molecular breeding and their products according to the current state of scientific knowledge. They also emphasise that preventing important innovations can also entail considerable social costs and risks for people and the environment.
“From a scientific point of view, no novel risks are discernible and actually not even theoretically conceivable. Why? Because these plants are indistinguishable from the products of traditional plant breeding. They carry only simple mutations, which can also occur naturally at any time. And this makes these genome edited varieties at least as safe as any variety created by conventional mutation breeding.”
How security is currently evaluated
The approval of novel foods is strictly controlled in many countries. They are to be safe and must not endanger health. In the EU, an independent expert panel of the European Food Safety Authority (EFSA) is responsible for approval. There, manufacturers of products made from genetically modified plants have to submit extensive studies concerning any changes at the molecular level, potential toxicity and allergy triggers.
This is particularly important in cases where a new gene has been transferred, and the plant correspondingly produces a protein that has been altered or is foreign to the species. If this protein or a related other ingredient was not previously present in the diet, it must be ruled out that they are harmful or allergenic. In addition, a comparison is made with the conventional counterpart. Because in principle, food from genetically modified plants must be equally safe.
“The risk research conducted over the past decades has shown us that according to everything we know, risks emanate from the breeding product and not from the breeding method. This means you can breed dangerous things, of course, but you can do that with genetic engineering, genome editing, or conventional breeding as well. That is the reason why the approach is wrong to create a law that focuses on the breeding method and therefore treats one method entirely different than another method. The right way would be to have a sensible risk assessment procedure based on the product. When it comes to a plant with a new trait, you have to check: What happens with it in nature? Does it affect human health? Only if it is declared safe after testing it can be approved.”
If a genetically modified product passes the tests and receives a positive report from EFSA, it can be approved for cultivation or commercialisation. The final decision is not made by the committee itself, but ultimately by the EU Commission. For some years now, however, the member states have had the option of imposing a national ban on cultivation. As a rule, product approval is granted for a period of ten years, after which it must be re-evaluated by EFSA.
If certain genome edited plants were to fall outside the scope of genetic engineering law in future, this complex approval process would no longer apply. From a scientific point of view, this is justifiable for products that could just as well have been created by traditional breeding methods or natural genetic changes.
