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TAKE ACTION: Click here to ask EPA to ban Monsanto’s insecticide-producing GMO crops! A new study shows that low doses of Bt biopesticide CryA1b as well as the glyphosate herbicide, Roundup, kill human kidney cells. The Bt biopesticide conferring insect resistance and the glyphosate tolerance trait tied to the use of glyphosate herbicides account for almost all the GM crops grown worldwide. Bt crops already constitute 39% of globally cultivated genetically modified (GM) crops, yet this is the first study that provides evidence on the toxicity of Bt protein in human cells.

This work comes at a time when the French environment and agricultural ministers are seeking an EU-wide ban of Monsanto’s MON810 Bt corn variety that is already outlawed in Hungary, Austria, Germany, Greece, and Luxembourg. The EU commission approved this crop in 2009, concluding that it “is as safe as its conventional counterpart with respect to potential effects on human and animal health”. In response to their publication the research team raised questions about the safety assessment procedure stating that their findings were a “surprising outcome and this risk was somehow overlooked” in past assessments of such crops.

The research team led by Gilles-Eric Seralini at the University of Caen, France, is already well-known for their investigations on the endocrine disrupting effects of glyphosate herbicides (see Glyphosate Kills Rat Testis Cells, SiS 54).The researchers tested the effects of Cry1Ab and Cry1Ac proteins as well as their combined effects with the herbicide Roundup on the human kidney cell line HEK293. Humans are exposed to hundreds of chemicals in a day, and their combined effects need to be understood. This is particularly important when considering the new generation of ‘stacked’ genetically modified (GM) crops now on the market, which carry multiple resistance genes for Bt toxins and glyphosate tolerance together.

Experiments were performed to assess both cell death and cell membrane integrity, as the pesticidal activity of Bt toxins results from creating pores in the membrane of cells in the insect gut. Cell death was measured using three parameters: 1) mitochondrial succinate dehydrogenase enzyme activity as a general cell death marker, 2) activity of the membrane-bound enzyme adenylate kinase  (AK) to assess membrane integrity as a marker of necrotic cell death and 3) caspase 3/7 activity, as a marker of apoptosis (programmed cell death). They found that Cry1Ab caused cell death at concentrations of 100 parts per million (ppm), according to mitochondrial succinate dehydrogenase activity. The membrane-bound enzyme adenylate kinase (AK) goes up in activity when the membrane disintegrates and releases the enzyme into the culture medium. Cry1Ab at 100 ppm induced a 2-fold increase in AK activity. No effects were seen with Cry1Ac.