Serious Lack of Scientific Data on the Effects of Bt toxins
THIRD WORLD NETWORK BIOSAFETY INFORMATION SERVICE
Two new studies shed further light on the Cry toxins from Bacillus thuringiensis (Bt), which are used in genetically modified (GM) insect-resistant crops.
The first study looks at the combinatorial effects of Cry toxins in stacked GM crops. Currently, there are no operational guidelines for testing procedures on how possible interactions of the toxins can be assessed in a risk assessment. The researchers found that the current knowledge on modes of action for Bt toxins is “clearly incomplete”, largely based on one laboratory study with a target pest species using a minimal combination of microbial Cry toxins. They also found that current measurements of efficacy were bound to result in sub-lethal and chronic effects being overlooked.
The second study summarizes the relevant information currently available regarding the biosafety and biological effects that Bt and its insecticidal Cry proteins elicit in mammals. The researchers discuss experimental studies performed on humans, mice, rats and sheep as well as in diverse mammalian cell lines. They find that some of the studies reviewed have demonstrated the capacity of these toxins to activate the immune system, which could produce allergic responses.
The researchers recommend expanding the parameters for evaluating the toxicity of Cry proteins beyond just the general aspects to more comprehensive examination of the systems, organs, tissues and cells, especially the gastrointestinal tract, the immune system, the genitourinary tract and the respiratory and nervous systems. They call for further studies on the sub-chronic, chronic and immunotoxicological effects of Cry toxins, particularly on humans.