Epidemiological studies have suggested an association between chronic glyphosate exposure and certain cancers. One study, done in Sweden, found that those diagnosed with non-Hodgkin's Lymphoma were 3.04 times more likely to report a history of glyphosate exposure compared to those without cancer, suggesting that glyphosate may increase the risk of this disease. Another study, using populations in Iowa and North Carolina, suggested a possible association between glyphosate exposure and multiple myeloma.
Glyphosate also appears to be a potent endocrine disruptor with pronounced effects on testosterone production in males. Studies on male rats demonstrate the glyphosate inhibits testosterone related enzymes and decreases the levels of testosterone in a dose-dependent manner. Compared to control rats, those exposed to the highest dose of glyphosate produced only ½ of the testosterone. Another rat study utilized doses of glyphosate which have been found in samples of human urine (1 ppm) and demonstrated that this dose reduces testosterone production by 35%! The same study showed that higher doses cause testicular cell death. A study on human reproductive cell lines demonstrated that endocrine disrupting effects start at a dose of 0.5 ppm. Genotoxic effects started at a dose of 5 ppm and cytotoxic effects started at 10 ppm. The glyphosate residual that is allowed by federal regulations is 400 ppm in animal feed, 200 ppm in spearmint and peppermint tops, 85 ppm in sunflower and safflower seeds, 30 ppm in barely and cereal grains like rice, 30 ppm in molasses, 20 ppm in soybean, and 5 ppm in corn, legumes and quinoa, just to name a few. Assuming that the average person has 5 liters of blood, one could experience blood levels of glyphosate at 0.5 ppm from eating 125 grams (or roughly 4.4 ounces) of soybeans or 29 grams (1 ounce) of sunflower seeds (note that small bags of sunflower seeds are often 5 ounces or more).
In addition to glyphosate toxicity, we should be concerned about possible toxicity from other GMO associated pesticides like Bt (bacillus thuringiensis) toxin. The effects of ingesting this GMO crop produced pesticide have hardly been studied. I found only one study, an in vitro study on human cells, and the results indicate the Bt toxins Cry1Ab and Cry1Ac do trigger cell death at moderate concentrations. Additionally, these pesticides appear to interact with glyphosate (which often accompanies them on food) with unpredictable consequences.
The issue of interaction effects in toxicology is a very serious one that is poorly studied or not studied at all. Of 80,000 chemicals in production, very few have been studied in combination, let alone the extremely common combinations that are found in the environment and in various products. For instance, glyphosate is rarely used alone, yet studies still evaluate its toxicity alone. Glyphosate products contain adjuvants or surfactants that enhance its herbicidal activity. One study did, in fact, look at the effects of glyphosate and its adjuvants (like POE-15) on human cell lines. The results showed that the combination was much more toxic than glyphosate alone!
It needs to be mentioned that the levels of glyphosate exposure from food and the complexity and doses of pesticide combinations (and their interactions) are likely to increase as a result of progressing glyphosate resistance. Just like antibiotic resistance among pathogenic bacteria, the target plants (i.e. weeds) for glyphosate are rapidly evolving a resistance to the pesticide as a result of its intensive use. In order for glyphosate to work on these plants, higher and higher doses are needed, or additional pesticides must be applied simultaneously. Currently there are 24 weed species listed with resistance to glycine pesticides, the pesticide class of glyphosate.
To be fair, internal studies done by Monsanto (the owner and producer of glyphosate) in the early 1980's show glyphosate to be relatively non-toxic. These are the studies submitted to regulatory agencies for approval and then used to set regulatory limits on public exposure and environmental contamination. For example, the EPA uses this 30 year old data for its Integrated Risk Assessment System (IRIS). These reviews often take 10-20 years to complete due to inadequate EPA funding, making them outdated the moment they are published! Again, no one is out there protecting our health. You can browse the EPA glyphosate review here if interested: http://www.epa.gov/iris/subst/0057.htm
Environmental and ecosystem effects of agricultural GMOs:
In addition to the possible harm of GMOs and GMO associated pesticides on the microbiome, cells, and physiology of humans and other mammals, there is concern about environmental effects (which always end up affecting the health of the environment's inhabitants as well). These environmental effects involve the same or similar mechanisms as those above. For example, GMO genes can transfer to environmental (soil and aquatic) microorganisms as well as native plants (like grasses) and possibly other food crops (like organic corn and soy, the fields of which may become contaminated with GMO seeds).
Additionally, GMO associated pesticides or toxins may negatively impact helpful insects (like predator or carnivorous arthropods) as well as target insects, selecting for the emergence or immigration of new, more resistant, pests. Similarly, intensive use of glyphosate may kill plants which support critical pollinators. For instance, glyphosate use has reached levels which are now killing milkweed, thus jeopordizing the monarch butterfly habitat and leading to a decline in their numbers.
Additionally, glyphosate and Bt toxin accumulate in the soil due to serial applications, leading to escalations in soil contamination, and glyphosate has been shown to contaminate most agricultural watersheds,.
The environmental effects of GMOs and GMO associated pesticides have barely been studied and the consequent effects on biodiversity and groundwater (drinking water) are uncertain.
Don't Throw the Bathwater Out With The Bathwater
To be fair, I need to mention the supposed intentions behind GMO agriculture promoted by the industry. Clearly, there is a profit motive as there exists a powerful synergistic feedback cycle in the consumption of proprietary pesticides and proprietary pesticide resistant seeds. However, GMO advocates sincerely, I believe, also hope that the technology can do good in the world.
For instance, "Golden Rice" is genetically modified rice which possesses the genes to produce beta-carotene. Beta-carotene is the precursor to vitamin A in humans, and in regions of Africa and Asia, vitamin A deficiency is extremely common (causing a number of severe problems such as blindness). Therefore, this rice could effectively reverse the epidemic of vitamin A deficiency. Such medical and public health applications of GMO technology do appear to be much more reasonable than the pesticide resistant varieties (which are largely admired because they make agriculture more simple). However, the potential health implications of medical or public health oriented GMO technology are largely the same as all other GMO technology with regard to gene transfer and insertional mutagenesis.
Even more relevant, however, is that the vitamin A deficiency in much of the world can be remedied in several other ways, many of which will have additional health benefits than just supplying beta-carotene. The vitamin A deficiency in much of the world is a result of a subsidized grain (largely rice) diet, which is a product of World Bank, World Trade Organization, and UN economic incentives and agreements aimed at increasing the economic output of developing nations. If the people of these nations were growing food for themselves and not for export, they would likely grow more diverse plant foods. Beta-carotene is widely abundant in the plant kingdom. Basically any plant food with a yellow, red, orange, and dark green color is likely to contain significant amounts of beta-carotene. Essentially, rice is not the solution to the vitamin A deficiency, it is the cause of it. This is a larger problem and a more difficult one to reverse, for sure, but we need to recognize the difference between real solutions which address the root problem and superficial solutions which simply compensate for one consequence of the problem. Failure to do so will accelerate our decline down the slippery slope of unintended consequences.
For additional research on GMOs on the GreenMedInfo.com database: Health Guide: GMO Research
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