The Politics, Public Health and Environmental Concerns of Genetically Engineered Salmon

Reading time: 7 – 11 minutes

So-called “Frankenfood” — genetically-modified organisms meant for human consumption or use as animal feed — has been making headlines again. This time, the buzz is over the FDA’s recent completion of their evaluation of the first genetically-engineered (GE) salmon meant for human consumption, the AquAdvantage salmon. The White House’s Office of Management and Budget is now reviewing the evaluation, which puts the AquAdvantage salmon one critical step closer to finding its way into farms and onto plates. While the GE salmon would be the first genetically-modified animal approved for human consumption, it’s not the first genetically-modified organism (GMO) used for food; data from 2009 indicate that 93% of soy and cotton, and 86% of corn grown in the U.S. are GMO [1]. There are a number of other common GMO crops, and GMO rice will likely become available soon.

GMOs aren’t the same as clones, and they’re not plants or animals whose traits have been “directed” through selective breeding. Such breeding to produce or enhance desired characteristics has taken place in animal and crop species for thousands of years. Cloning, on the other hand, is the process of creating identical copies of a species, but does not introduce new genes into an organism. GMOs have had specific genes — generally from bacteria, other plants, or other animals — added into their genome to produce traits that the organisms can’t produce on their own. The resulting transgenic organisms therefore express both their own normal proteins and those of other organisms.

Concerns with plant GMOs

While proponents of GMO crops and food tout the benefits, including faster growing times, increased yields, and crop resistance to pests and pesticides, opponents cite a number of concerns. Among these is concern for the environment. Some of the most widespread of the GMO crops are “Roundup Ready,” meaning they’re resistant to the herbicide glyphosate, which is commonly used on crop fields to prevent weeds. Glyphosate kills plants by interfering with the synthesis of three amino acids: phenylalanine, tyrosine and tryptophan. Glyposate resistance comes from a modified gene — 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), isolated from a bacterial strain resistant to glyphosate — that is inserted into the crop genome.

From an agricultural standpoint, a Roundup Ready crop seems like a wonderful thing, since it allows the farmer to spray crops with Roundup herbicide, thus reducing weeds and increasing crop yields, without risking the crops themselves. There are a number of problems with the technology, however. The first of these is that glyphosate is toxic (especially in the quantities currently being used), and is also very affordable. The assurance of a glyphosate-resistant crop plant means that the easiest way to ensure a weed-free crop is to use very large amounts of glyphosate. The excess herbicide then sinks into the ground and may percolate into the groundwater, or washes out of the field with irrigation, and ends up in the waterways. Both cases represent a risk to the environment and to humans. Further, it’s possible for plants to transfer genes between species. This means that glyphosate-resistant crops can confer resistance to weeds — such glyphosate-resistant “superweeds” have already been identified — which necessitates the use of larger and larger quantities of glyphosate and/or other, more toxic herbicides to control weed propagation. This amplifies the environmental threat.

Furthermore, humans are exposed to glyphosate residue on glyphosate-resistant GMO crops that are consumed as food, which represents an additional route of exposure to the toxin. An article in the International Journal of Biological Science reports finding significant health effects associated with mammalian consumption of GMO corn [2]. One of the three varieties tested was a glyphosate-resistant species. The other two were so-called “Bt corn,” which contains a gene from the bacterial species Bacillus thuringiensis. The inserted gene codes for production of a pesticide inside the corn plant itself, which helps to protect the crop from insect predation. Humans or animals eating the crop, then, consume the pesticide. All three GMOs included in the study resulted in negative health effects on rats over a period of 90 days, though the effects of glyphosate-resistant corn were the most significant. These effects included damage to the liver, kidneys, adrenal glands, heart, spleen, and blood-forming tissues and cells.

Another issue is that GMOs express proteins — and therefore potential allergens — that aren’t native to the non-modified organism. With allergies on the rise in industrialized nations, this is a serious concern. Researchers reported finding an allergen from the Brazil nut in certain GMO soy [2]. The Brazil nut gene was introduced into the soy in order to cause the beans to produce more methionine, an amino acid in which they are otherwise quite low. The idea was to increase the nutrient value of the soy.

The problem here is that if a GMO (such as the methionine-enriched soy) expresses allergens from other organisms (such as the Brazil nut), it increases the likelihood of serious allergic reactions to the GMO. While the Brazil nut/soy GMO was abandoned and is not being grown, it nevertheless exemplifies the potential for increased allergic potential of GMOs as compared to non-GMO food. This problem is amplified by the fact that currently, the FDA does not require labeling of GMOs and GMO-containing products, though there is a campaign to change that policy.

Animal GMOs possess additional concerns

Some of the concerns associated with GMO crops, such as herbicide use and pesticide production, don’t apply to animal GMO species such as the AquAdvantage salmon. However, animal GMOs raise additional issues. The AquAdvantage salmon is an Atlantic salmon (Salmo salar) with inserted genes from the Chinook salmon (Oncorhynchus tshawytscha) and another fish called a pout (Macrozoarces americanus). The inserted genes help the AquAdvantage salmon to produce growth hormone year-round, resulting in much faster growth. Farmed AquAdvantage salmon would reach market weight faster and could provide an abundant food source. The genetics of the AquAdvantage salmon render them all female, and most (approximately 98%) are sterile. They’re intended for farming, not for release into the wild. However, one of the concerns expressed by environmental organizations is whether they could escape into the wild, and whether the small percentage of non-sterile individuals could breed with wild salmon. There is very little existing information on what impact that could have upon the environment. Further, salmon farming has a significant and negative environmental impact in its own right, and farmed Atlantic salmon are listed by the Environmental Defense Fund as a “Worst [Food] Choice” with regard to environmental concerns. The farming process also means farmed salmon are high in polychlorinated biphenyls (PCBs), which are toxic industrial compounds. As such, the Monterey Bay Aquarium’s Seafood Watch suggests avoiding farmed Atlantic salmon. Furthermore, the diet farmed salmon are fed changes their nutritional profile. While wild salmon are high in heart-healthy omega-3 fatty acids, farmed salmon have lower levels of these, and instead have high levels of omega-6 fatty acids, which are much less healthy. The environmental and health impact of a transgenic Atlantic salmon would, at the very least, be as detrimental as that of a non-GMO Atlantic salmon, with the additional concern that GMOs are developed to be produced in great abundance, multiplying the environmental and health impact.

Known environmental and health effects of farmed Atlantic salmon aside, perhaps the most major consideration with regard to the AquAdvantage salmon is simply that there’s very little information available on the long-term ramifications and effects of a transgenic food animal. As the potential first such animal, the AquAdvantage salmon is in a position to set precedent that other GMOs will surely follow. The Union of Concerned Scientists has expressed that the FDA is poised to set the bar quite low.

References

1. Genetically Modified Crops: Soybean, Maize, Rapeseed, Cotton. GMO Compass. Accessed 2011 Oct 23.
2. Spiroux de Vendomois et al. A comparison of the effects of three GM corn varieties on mammalian health. Int J Biol Sci. 2009 Dec 10;5(7):706-26.
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3. Nordlee et al. Identification of a Brazil-Nut Allergen in Transgenic Soybeans. N Engl J Med. 1996 Mar 14;334(11):688-92.
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