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GM health risks


Key Information

GM crops are not 'green'. No plants with benefits to consumers or the environment have materialized, despite repeated promises by biotech corporations. Evidence has been accumulating over the years that GMO crops often have a negative impact on the environment. They have contaminated non-GM crops and wild plants, increased the use of toxic chemicals, created 'superweeds' and reduced biodiversity. GM crops can never be recalled after their release nor can they "co-exist" with conventional and organic crops without contaminating them crops, denying people the right to choose GM free food.


GM crops cause widespread contamination of other crops and wildlife

GM seeds and crops can easily cross contaminate wild and domestic plants through wind-borne pollen, seed dispersal, volunteers, and horizontal gene transfer. They can also contaminate related and unrelated species, including soil micro-organisms and bacteria living in the guts of humans and animals through a process called horizontal gene transfer.

There are a number of ways in which a GM crop may cause contamination:

Cross-pollination of neighbouring crops or related wild species.

Seed spilt at harvest that germinates and contaminates later crops grown in the field.

Seed split around fields and on verges during transport after harvest.

Mixing of GM and non-GM crops in storage or during distribution. Grain stores or equipment may not be cleaned out properly, or mistakes may be made by operators leading to mixing or errors in labelling.

The GeneWatch UK and Greenpeace worldwide register of GM contamination lists over 300 incidents.


GM pollen can travel long distances on the wind or via insects and cross-pollinate non-GM crops, wild crop plants or weed crop plants in following crops, as well as wild relatives. Contamination of non-GM crops causes economic losses for farmers, wild plants may incorporate several GM traits creating so called 'superweeds'1, and traditional crop varieties can be contaminated. In Mexico, where no GM maize was grown but food and animal feed imports were allowed, local varieties of maize still became contaminated with GM2.

The GM industry is advocating the idea of setting separation distances between GM and non-GM crops to limit cross-pollination. However low levels of pollination (0.1-0.3%) can be found at quite long distances of several hundred metres and only decline very slowly. This makes it difficult to determine what distances will be required to restrict contamination to any particular level. 3

Seed sterility (Terminator technology)

Another response to this threat has been to develop further genetic modifications of the plant that attempt to reduce or eliminate gene flow by altering the plant's reproductive processes. The most notorious of these is 'Terminator technology', where a crop produces sterile seeds. This 'biological containment' is being promoted as a way of preventing cross-contamination. While sterile seeds to prevent gene flow may be presented as safety mechanisms for PR purposes, their main purpose is an economic one - to prevent farmers keeping seed for future use or to reduce possible liability claims for contamination, for example.

Terminator technology is one of the most contested applications of GM to crops. It involves genetic modification of a plant so that the seed from the crop will not germinate if farmers keep it for resowing. Terminator technology uses a chemical sensitive genetic switch (responsive, for example, to alcohol or the antibiotic tetracycline) linked to a gene for an enzyme which activates a toxin gene. When the toxin gene is switched on, it becomes active in the late stage of seed formation; it does not prevent the seed forming but will prevent it germinating. The genetic switch may act either to suppress or activate the enzyme and toxin so switches germination either on or off. It is anticipated that the switch would generally be used to suppress germination - the chemical would be applied to the seed before it is sold to farmers to prevent seed saving and resowing. In terms of gene containment, because the seed is sterile, any hybrids formed will be sterile and seed shed at harvest will not survive and germinate in later years: one dimension of gene flow is limited. However, the system is complex and largely experimental and has several shortcomings in terms of gene containment.

Terminator crops will still produce pollen and could cross with neighbouring non-GM or organic crops. The GM traits could therefore contaminate non-GM food or feed and compromise fertility if farmers had been intending to save seed from their crops.

Treatment of seeds before sale may not be completely effective. In fact, for any use of genetic switches, it is difficult to imagine that sufficient chemicals could be applied to millions of seeds in sufficient concentrations to reliably trigger the switch in every case. The effect may be sufficient to make saving seed an unreliable exercise for farmers, but not enough for complete gene containment.

There may be gene silencing or instability of one component leading to failure of the system. Depending on which gene was affected, there would be seed sterility at the wrong time (during seed production), or it would not occur when required (after sale to farmers). Gene silencing is one phenomenon seen in GM crops that arises from the introduction of foreign genes.

The chemical sensitive genetic switch may be activated by some of the plant's own chemicals or may not be completely switched off all the time. This 'leakage' could lead to fertile seeds being produced. Some of the chemicals used in studies using such switch technology can be harmful to the plant.

The genes forming the Terminator system have to be linked together to work properly. If they split during reproduction, the system would fail.

Terminator technology brings potential social and economic implications for the millions of poor farmers in developing countries who rely on farm-saved seed for survival. Terminator should never be allowed on these grounds alone. However, it is also not a reliable gene containment system for both technical and practical reasons.4

The potential for seed sterility and systems which are controlled by the external application of chemicals to increase dependency on seed corporations is extremely worrying. Ten multinational corporations are estimated to control around half of all the world's seed supply with Monsanto now the largest seed corporation globally.5 This consolidation has been facilitated by biotechnology and the advent of patents on genes and seeds allowing corporate control. Genetic Use Restriction technology would further add to this control.

Delta and Pine Land, the company behind Terminator, presents its technology as 'enhancing biosafety and biodiversity'.6 This company and the many others, including Monsanto and Syngenta, developing systems to control the reproduction and use of GM crops for economic reasons, were damaged by the international protest against their plans. Forced to make statements that they would not develop Terminator crops, they now seem to be seeking a more acceptable image for their intentions. To allay fears about contamination they present the technology as for 'biological containment'.

Because of the serious social and economic consequences of Terminator technology, especially on poor farmers, there is an ad hoc international moratorium on its development under the Convention on Biological Diversity (CBD). However, in February 2005, during a meeting of the CBD, a leaked memo revealed that the Canadian government was seeking to reverse this position. Several governments began to attack a report of an advisory group which had concluded that the disadvantages of Terminator far outweighed any potential advantages in terms of gene containment.38 The International Seed Federation, representing the world's largest seed producers who stand to benefit from an end to farm-saved seed, are also still interested in Terminator.7


New 'super-weeds' may evolve which will be difficult or even impossible to eradicate.

One of the potential risks of GM crops is that the introduced genes will be passed to other non-GM crops or related wild plants. This could result in the contamination of foods or the evolution of new, more competitive weeds, causing problems for farmers or ecosystems. If the gene transferred was coding for a drug, as part of an attempt to make medicines in plants, the consequences of contamination of food could be particularly serious.

In Canada, where GM oilseed rape has been grown for six years, super-weeds that are resistant to three herbicides are already a problem for farmers. GM oilseed rape has pollinated other rape and the seed left in the field after harvest grows as a weed in the next crop. Farmers are turning to more toxic chemicals such as 2,4 D and paraquat to control them.

In the USA emergence of herbicide resistant weeds associated with use of GM crops. As a result of using herbicide tolerant Roundup Ready crops, and soybean in particular, evolution of herbicide-resistant weed populations attributable to the herbicide-resistant crop/herbicide program has been observed. Horseweed (Conyza canadensis), that is resistant to Roundup (glyphosate) is becoming a problem weed for some soybean farmers. Four to thirteen- fold increases in resistance to Roundup were recorded in horseweed within three years of the introduction of Roundup Ready soybeans. This is not due to gene transfer, but simply the selection pressure exerted by the herbicide. Resistance to Roundup has also been detected in another four weed species. The presence of resistant weeds may drive up the use of other, more damaging herbicides.


Pollution arising from the use of harmful chemicals may increase

80% of the crops grown commercially have genes added so the crop is no longer killed by chemical weedkillers (herbicides) so farmers can spray the chemicals and kill the weeds but not the crop. Most of the rest have genes added which produce a toxin so that insects feeding on the crop are killed.

Roundup Ready soybeans, the most extensively grown GM crop today, has led to an increase in herbicide use. Independent reports from the US show that since 1996, GM corn, soybean and cotton have led to an increase in pesticide use of 122 million pounds (55 million Kilos). 8

The biotechnology industry has claimed that GM crops will allow farmers to use less chemical weedkillers and insecticides. The majority of GM crops being grown worldwide are tolerant to Monsanto's weedkiller, Roundup, or Bayer's weedkiller, Liberty. The companies making the chemicals also sell the GM seed. However, in North America - where GM soybean, cotton and maize are grown on thousands of acres - the use of weedkillers has not been reduced. Sales of Roundup and Liberty have increased and new factories are being built to make more.

The companies argue that Roundup (glyphosate) and Liberty (glufosinate) are less damaging to the environment than other chemicals even though they kill almost all green plants they contact. However, sometimes GM Liberty tolerant maize has not performed well and the old chemicals, such as atrazine, have been reintroduced to control weeds.

The only case where chemical use has been reduced is GM cotton with an inbuilt insecticide called Bt. Conventional cotton production often involves many - often 8 or 9 - applications of insecticide and Bt cotton has reduced this. However, the reduction may be short lived as many farmers are not following plans to prevent insects developing resistance to Bt. Furthermore, some varieties of Bt cotton have been removed from sale in India due to their poor performance.


GM crops increase pesticide use

Spraying pesticidesOver a decade of experience in the US, Argentina and Brazil demonstrates that GM crops have contributed substantially to rising pesticide use and an epidemic of herbicide-resistant weeds.9 Resistant weeds have prompted biotechnology firms to develop new GM crops that tolerate heavier applications of chemicals, and tolerate two herbicides rather than just one, promoting pesticide use even further. The use of mechanical tillage to control resistant weeds is also increasing, contributing to greater soil erosion and global warming gas emissions.

In the US, when GM crops were first grown, the rising use of glyphosate on Roundup Ready crops was more than offset by reductions in the use of other pesticides. As of 2000, however, weeds that could no longer be controlled with the normal dose of glyphosate began to emerge, driving farmers to apply more. Thus, the widespread adoption of Roundup Ready crops combined with the emergence of glyphosate-resistant weeds has driven a more than 15-fold increase in the use of glyphosate on major field crops from 1994 to 2005. The trend continues. In 2006, the last year for which data is available, glyphosate use on soybeans jumped a substantial 28%, from 75,743 million lbs in 2005 to 96,725 million lbs in 2006. More and more farmers are being told - by agronomists and by Monsanto - to combat glyphosate-resistant weeds by applying other chemicals, such as paraquat, diquat and atrazine, often in combination with higher rates of glyphosate.USDA pesticide data confirm this trend: rising glyphosate use even while use of other more toxic herbicides also increases, or at best remains constant.

In Argentina, overall glyphosate use has more than tripled from 65.5 million litres in 1999/2000 to over 200 million litres in 2005/6. In 2007, agricultural experts reported that a glyphosate-resistant version of Johnsongrass (Sorghum halapense) was infesting over 120,000 ha of the country's prime cropland. Johnsongrass, an extremely damaging perennial, is a monocot weed that is considered one of the worst weeds in the world, and resistance to glyphosate will make it all the more harder to control. The emergence of glyphosate-resistant Johnsongrass is directly attributable to the huge increase in glyphosate use associated with near total dependence on Roundup Ready soybeans in Argentina. The main recommendation to control resistant weeds is to use a cocktail of herbicides other than glyphosate, including more toxic weedkillers such as paraquat, diquat and triazine herbicides such as atrazine. It is estimated that an additional 25 million litres of herbicides will be needed each year to control resistant weeds, resulting in an increase in production costs of between $160 and $950 million per year.

In Brazil, government agencies show that the consumption of the main active ingredients in the most heavily used soya herbicides increased by 60% from 2000 to 2005. Use of glyphosate grew 79.6% during this period, much faster than the increase in area planted to Roundup Ready soya. Several factors make it virtually certain that the number of weeds resistant to glyphosate and their prevalence will continue to rise dramatically in the future. These factors include: 1) More planting of glyphosate-tolerant crops in rotation (every year) 2) Continuing dramatic increases in the use of glyphosate; 3) New glyphosate-tolerant crops on the horizon, including some that are engineered to withstand higher doses of glyphosate. As a result, overall use of toxic weedkillers to kill increasingly resistance weeds is bound to increase, with adverse effects on human health (especially farmworkers) and the environment.

Wildlife and biodiversity is being harmed by new toxins and changes in agricultural practices.

The intensive cultivation of soybeans in South America is fostering deforestation, and has been associated with a decline in soil fertility and soil erosion.10

The gradual disappearance of birds from our farmland has shown us how agricultural practices can harm wildlife. The UK's farm-scale evaluation with two of the first GM crops that could be grown here, herbicide tolerant oilseed rape and sugar beet, showed that their use would be likely to lead to further declines in farmland wildlife. The UK Government's four-year Farm Scale Evaluations looked at the impact of growing herbicide tolerant GM crops on farmland wildlife, and found negative impacts associated with growing GM beet and oilseed rape. GM maize came out better than its conventional equivalent, but the comparison was flawed because the conventional maize in the trials was grown using the extremely damaging weedkiller, atrazine, which is now being phased out in Europe11.

Insect resistant crops also have associated environmental problems. There are concerns about the impact of such crops, which produce an insecticide throughout the plant, on non-target organisms, such as butterflies, moths and other invertebrates12. There is also little research on this impact that is relevant to European farming and species13 and little evidence on the impact on soil organisms. Yet when these issues were raised by Member States in relation to the approval of such crops, the EFSA GMO Panel failed to take such concerns seriously14. However, EC documents forming part of the EC's defence in the GM dispute at the World Trade Organisation state that "it is a reasonable and lawful position" that insect-resistant crops should not be planted until all the effects on the soil are known15.

There are many wider social and environmental problems associated with intensive soya production - whether GM or not. These include forest and other habitat destruction, removal of local communities from their land and threats to food sovereignty16. Intensive farming of animals for meat and dairy products depends on, and fuels the growth of, vast amounts of high protein soya. There is currently enough non-GM soya being grown in Brazil to satisfy European demand, but growing demand for meat from countries like China means that the current system is simply not sustainable.

Read more

Genetically modified animal feed Briefing, FoE, May 2006, available from Friends of the Earth.

Case study Argentina and GM soya

Argentina has adopted GM soya on a large scale - more than 14 million hectares of 'RoundUp Ready' glyphosate-resistant soya was planted in 2003-4. Communities living near to soya cultivation have been seriously affected by the spraying of herbicides. One study in Loma Senés described how a small community surrounded by large areas of land rented out for soya production found their crops and livestock destroyed by aerial spraying of glyphosate.

The increase in the area cultivated for soya has been responsible for deforestation in provinces all over the country. In Entre Ríos almost 1.2 million hectares of forest has been removed in the last few years, in part due to a doubling of the area cultivated for soya between 1994 and 2003 to 1,200,000 hectares in 2003.17.


Threat to Biodiversity

As well as the potential for economic losses as a result of contamination of non-GM crops, GM organisms could cause environmental harm. Potential adverse effects include the genetic contamination of related wild species and impacts on ecosystems if the GM crop itself becomes invasive. Critical debate of environmental liability has been lacking and the Government has used this to avoid addressing the issue.

Pest resistance

The use of GMO seeds and crops which are modified to increase pest-resistance often end up producing the opposite effect, as the pests adapt and become resistant to the poisonous crops. Widespread failure of Monsanto's GMO Bt cotton crops in India resulted in thousands of farmers going bankrupt and hundreds committing suicide.


Just as the use of antibiotic drugs has led to antibiotic-resistant "superbugs" that are difficult if not impossible to control, the widespread use of weedkillers (herbicides) such as glyphosate and glyphosinate ammonium has led to the proliferation of herbicide-resistant "superweeds". The release of Monsanto's "Roundup Ready" and other patented GMO crops which are genetically modified to be resistant to weekillers increases the spraying of weedkillers, which, in turn, has produced a veritable plague of "superweeds". The use of glyphosate increased dramatically in the mid-1990s with the introduction of crops genetically modified to tolerate the herbicide. In addition to soybeans, varieties of corn, cotton, oilseed rape (canola), sorghum and alfalfa also have been developed to allow the post-emergence use of the herbicide. As of January 2007, scientists have confirmed at least ten glyphosate-resistant weeds worldwide. They include common ragweed, giant ragweed, horseweed, tall waterhemp, buckhorn plantain, goosegrass, hairy fleabane, Italian ryegrass, palmer amaranth and rigid ryegrass. According to Ray Massey, an agricultural economist at the University of Missouri, USA, it is not uncommon for farmers to believe "that resistant weeds aren't a problem until they occur on my land". He said "there's a belief that a silver bullet will come along, but there isn't another silver bullet. I just don't see it happening." He said "It might be more expensive upfront, but working to prevent glyphosate-resistant weeds from ever developing is more economical in the long run". Once superweeds have developed, eradicating them is an extensive proposition requiring the use of multiple and stronger, more toxic weedkillers, thus causing new agro-environmental problems as well as higher production costs for farmers. Note that a 2005 study found that the glyphosate and glyphosinate based weedkillers such as Roundup are 10 times more toxic than previously thought (see next article below). 18

Increased use of weedkillers Monsanto's Roundup weedkiller, which contains the chemical glyphosate, is the world's most common agricultural herbicide. It is widely used on Irish farms and may also be used in Coilte's monoculture tree plantations. Roundup herbicide causes sudden crop death. It is lethal to frogs, and highly toxic to human placental cells, even at one-tenth the recommended dosage. (It is already linked to cancers, neuro-defects and spontaneous abortions.) Genetically modified "Roundup Ready" crops have been responsible for increased use of the herbicide in recent years. Monsanto's sale of glyphosate has expanded approximately 20% each year through the 1990s, accounting for 67% of the company's total sales as of 200l. More Glyphosate is now being introduced into the environment and the human food chain through cultivation of GMO crops that are tolerant to the herbicide and contain glyphosate residues. A 2005 study of Roundup presents new evidence that the glyphosate-based herbicide is far more toxic than the active ingredient alone. The study, published in the June 2005 issue of Environmental Health Perspectives reports glyphosate toxicity to human placental cells within hours of exposure, at levels ten times lower than those found in agricultural use19. The researchers also tested glyphosate and Roundup at lower concentrations for effects on sexual hormones, reporting effects at very low levels. This suggests that dilution with other ingredients in Roundup may, in fact, facilitate glyphosate's hormonal impacts. Roundup is a mixture of glyphosate and other chemicals (commonly referred to as "inerts") designed to increase the herbicide's penetration into the target and its toxic effect. Since inerts are not listed as "active ingredients" the U.S. Environmental Protection Agency (EPA) does not assess their health or environmental impacts, despite the fact that more than 300 chemicals on EPA's list of pesticide inert ingredients are or were once registered as pesticide active ingredients, and that inert ingredients often account for more than 50% of the pesticide product by volume.

Monsanto is also driving greater use of Roundup by incorporating the Roundup Ready trait in nearly every GM seed it sells. US farmers who once bought GM maize modified only to be resistant to insect pests (Bt crops) now find these varieties "stacked" with the Roundup Ready herbicide resistance trait as well. As a result, in the US , the area planted with Monsanto GM maize seed without the Roundup Ready trait fell dramatically from 25.3 million acres in 2004 to just 4.9 million acres in 2008.

This "trait penetration" strategy means higher profits from both seeds and Roundup sales, and ensures farmers' dependence on GM traits and Roundup.20



1: Friends of the Earth (2004). GM Contamination Briefing 3: Gene Escape. http://www.foe.co.uk/resource/briefing_notes/gene_escape.pdf

2: Friends of the Earth Europe (2003). Provisional comments by Friends of the Earth Europe to the notification by Monsanto for the placing on the EU market of maize grains derived from insect-protected maize lines MON863 and MON863 x MON810 (notification number C/DE/02/9). http://www.foeeurope.org/GMOs/pending/MonsantoGM_Maize863.pdf

3: GeneWatch Uk, Briefing NO 29, October 2004, GROWING GM CROPS: The Need for Contamination and Liability Rules

4: Genewatch UK, Briefing No 33, December 2005, GM CONTAMINATION: Can biological containment work for crops and society?

5: ETC Group Communiqué (2005) Seed industry concentration - 2005. http://etcgroup.org/documents/Comm90GlobalSeed.pdf.

6: Report of the ad hoc technical expert group meeting on the potential impacts of genetic use restriction technologies on smallholder farmers, indigenous and local communities and farmers' rights (2003) UNEP/CBD/SBSTTA/9/INF/6. www.biodiv.org/doc/meeting.aspx?mtg=sbstta09&tab=1.

7: International Seed Federation (2003) Position on Genetic Use Restriction technologies. www.worldseed.org/Position_papers/Pos_GURTs.htm.

8: http://www.foei.org/publications/pdfs/gmcrops2006execsummary.pdf

9: www.foe.co.uk/resource/briefings/who_benefits.pdf

10: http://www.foei.org/publications/pdfs/gmcrops2006execsummary.pdf

11: GM Crop Trial Blow to Biotech Industry. Friends of the Earth Press Release 21 March 2005

12: See, for example, Felke M, Lorenz N & Langenbruch GA (2002). Laboratory studies on the effects of pollen from Bt-maize on larvae of some butterfly species. Journal of Applied Entomology 126(6):320., Hilbeck A, Baumgartner M, Fried PM & Bigler F (1998). Effects of transgenic Bacillus thuringiensis corn-fed prey on mortality and development time of immature Chrysoperla carnea (Neuroptera: Chrysopidae). Environmental Entomology 27(2):480-87., Jesse LCH & Obrycki JJ (2000). Field deposition of Bt transgenic corn pollen: lethal effects on the monarch butterfly. Oecologia 125(2):241-8., Prütz G & Dettner K (2004). Effect of Bt corn leaf suspension on food consumption by Chilo partellus and life history parameters of its parasitoid Cotesia flavipes under laboratory conditions. Entomologia Experimentalis et Applicata 111(3):179

13: Greenpeace (2005). Bt11 maize - C/F/96.05.10 notification for cultivation. http://eu.greenpeace.org/downloads/gmo/Bt11reportOct05.pdf

14: Friends of the Earth Europe comments on 1507 maize: Response to EFSA GMO Panel opinions for Commission questions EFSA-Q-2004-072 and EFSA-Q-2004-087. http://www.foeeurope.org/GMOs/pending/FOEE%20comments%20-1507%20maize.pdf

15: Friends of the Earth and Greenpeace (2006) Hidden Uncertainties: What the European Commission doesn't want us to know about the risks of GMOs http://www.foeeurope.org/publications/2006/hidden_uncertainties.pdf

16: Joensen L, Semino S & Paul H (2005). Argentina: A case study on the impact of genetically engineered soya.

Gaia Foundation. http://www.econexus.info/pdf/ENx-Argentina-GE-Soya-Report-2005.pdf and Greenpeace (2006) Eating up the Amazon http://www.greenpeace.org.uk/MultimediaFiles/Live/FullReport/7555.pdf

17: Joensen L, Semino S & Paul H (2005). Argentina: A case study on the impact of genetically engineered soya. Gaia Foundation. http://www.econexus.info/pdf/ENx-Argentina-GE-Soya-Report-2005.pdf and Greenpeace (2006) Eating up the Amazon http://www.greenpeace.org.uk/MultimediaFiles/Live/FullReport/7555.pdf

18: http://gmfreeireland.org/environment/index.php

19: Sophie Richard, Safa Moslemi, Herbert Sipahutar, Nora Benachour, and Gilles-Eric Seralini, Environmental Health Perspectives, Vol. 113, No. 6 June 2005, http://ehp.niehs.nih.gov/members/2005/7728/7728.html and http://ga4.org/ct/k71TIKE1WzfS/

20: http://www.foei.org/en/publications/pdfs/gmcrops2009exec.pdf/view