By Sayer Ji
a new study published in the Journal of Hematology& Thromboembolic Diseases indicates that the biopesticides engineered into GM crops known as Bacillus Thuringensis (Bt) or Cry-toxins, may also contribute to blood abnormalitiesfrom anemia to hematological malignancies(blood cancers) such as leukemia.
A group of scientists from the Department of Genetics and Morphology, Institute of Biological Sciences, University of Brasilia, Brasilia/DF, Brazil set out to test the purported human and environmental biosafety of GM crops, looking particularly at the role that the Bt toxin found within virtually all GM food crops plays on non-target or non-insect animal species.
The research was spurred by the Brazilian Collegiate Board of Directors of the National Sanitary Surveillance Agency (ANVISA), who advocated in 2005 for evaluations of toxicity and pathogenicity of microbiological control agents such as Bt toxins, given that little is known about their toxicological potential in non-target organisms, including humans.
While Bacillus Thurigensis spore-crystals have been used since the late 1960's in agriculture as a foliar insecticide, it was only after the advent of recombinant DNA biotechnology that these toxin-producing genes (known as delta endotoxins) were first inserted into the plants themselves and released into commercial production in the mid-90's, making their presence in the US food supply and the bodies of exposed populations ubiquitous.
What the new study revealed is that various binary combinations and doses of Bt toxins are capable of targeting mammalian cells, particularly the erythroid (red blood cell) lineage, resulting in red blood cell changes indicative of significant damage, such as anemia. In addition, the study found that Bt toxins suppressed bone marrow proliferation creating abnormal lymphocyte patterns consistent with some types of leukemia.
The researchers also found that one of the prevailing myths about the selective toxicity of Bt to insects, the target species, no longer holds true:
It has been reported that Cry toxins exert their toxicity when activated at alkaline pH of the digestive tract of susceptible larvae, and, because the physiology of the mammalian digestive system does not allow their activation, and no known specific receptors in mammalian intestinal cells have been reported, the toxicity these MCAs to mammals would negligible. However, our study demonstrated that Bt spore-crystals genetically modified to express individually Cry1Aa, Cry1Ab, Cry1Ac or Cry2A induced hematotoxicity, particularly to the erythroid lineage. This finding corroborates literature that demonstrated that alkali-solubilized Bt spore-crystals caused in vitro hemolysis in cell lines of rat, mouse, sheep, horse, and human erythrocytes and suggested that the plasma membrane of susceptible cells (erythrocytes, in this case) may be the primary target forthese toxins
The study also found:
1) That Cry toxins are capable of exerting their adverse effects when suspended in distilled water, not requiring alkalinizationvia insect physiology to become activated as formerly believed.2) That a dose of Cry1Ab as low as 27 mg/kg, their lowest tested dose, was capable of inducing hypochromic anemia in mice – the very toxin has been detected in blood of non-pregnant women, pregnant women and their fetuses in Canada, supposedly exposed through diet.
3) Whereas past reports have found that Bt toxins are generally nontoxic and do not bioaccumulate in fatty tissue or persist in the environment, the new study demonstrated that all Cry toxins tested had a more pronounced effect from 72 hours of exposure onwards, indicating the opposite is true.
4) That high-dose Cry toxin doses caused blood changes indicative of bone marrow damage (damage to "hematopoietic stem cell or bone marrow stroma").
The authors noted their results "demonstrate leukemogenic activity for other spore-crystals not yet reported in the literature."
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