I’m still in the fairly early stage of my process of self-education on the topic of genetically engineered crops so I ‘m bound to make a few entertaining howlers (not too many, I hope and of course I am very happy to have them pointed out). However, there is a mountain of information out there for anyone who genuinely wants to understand the subject so I have been taking a look at Bt – Bacillus Thuringiensis. (Thanks to this website which goes into it in great detail and this one, which adds some interesting extra details about the specifics of transgenic Bt.)
Bt is a naturally-occurring bacterium which was found in the early 20th century to be toxic to lepidoptera – moths and butterflies.It started being used as an insecticide in the nineteen-twenties but was never very popular because it was very specific to moths and didn’t last very long in the environment. By the 1950’s it was understood that the production of a toxic crystal protein (CRY protein) during spore production was responsible for the insecticidal property: this crystal is activated by the peculiarly alkiline environment of the insect gut and then binds to receptors in the gut of the insect larva and attacks the gut walls, causing death. There is some evidence that the actual cause of death is due to blood poisoning by bacteria released by the perforation of the gut walls. The CRY proteins of Bt strains are very specific as to which receptors they will bind to, making it a highly specific insecticide (hence its unpopularity in the early days, when a more general insecticide was desired).
Of course, this very specificity is highly desirable when you want to target only certain species, and once research work on Bt started in earnest, many strains were designed which extended the toxicity outside the moth family to other pests. This, along with the facts that the bacteria did not last long in the open and that the CRY proteins have no effect on fish, mammals, etc, meant that Bt has become a mainstay of the organic farming industry as well as conventional agriculture.
In the last twenty years or so, GE crops have entered the picture, and it didn’t take long for scientists to work out how to get the plants themselves to produce the CRY proteins by splicing a gene from the bacillus into the plant, and to extend the number of insects affected by them. Corn, potato, tomato and cotton have all been modified in this way.
So what is the difference between using Bt on organic produce and the transgenic CRY proteins used in GE crops? After all, they both rely on the production of the very same proteins. It turns out the difference is actually very significant because in traditional usage, the toxin-producing spores are sprayed or otherwise applied to the plant and break down very quickly if they are not eaten. The transgenic CRY proteins, by contrast, are expressed in every cell of the plant and hence cannot degrade in the environment or be washed off. Basically, we now have the opportunity to eat food products which contain a new ingredient.
Thus the question to be asked about transgenic Bt is simply whether or not it is harmful to humans and that’s where the search gets a little difficult. The position of the pesticide industry is that the CRY proteins are a naturally occurring substance which has never caused harm to humans, which is true, but it’s also true that the transgenic proteins are different from the naturally occurring variety (they are already soluble and don’t need the alkiline action of the insect gut to activate them).
I’d like to know more about this as it does seem to be an issue but finding information is difficult (as opposed to finding polemic: that’s easy!). GMWatch.org argues, as I do above, that the difference between regular and transgenic Bt could be significant (they say it is, without any evidence) but then spoil things by referencing a series of studies by Vasquez et al which they claim show ‘ill effects’ in animals when in fact, the first paper recommends the possible use of Bt to help aid in the efficient delivery of vaccines in cows!
All other studies I can find lead to Professor Gilles Seralini, or one of his students, and show some worrying findings but unfortunately, there don’t seem to be any studies which repeat them and rule one in science is that no study is worth anything until it has been independently repeated and verified. I’m always very suspicious of any body of research which constantly identifies the same small group of people as its authors – all valid and interesting research is always quickly picked up and carried forward by multiple teams, especially in a critical and potentially lucrative field like this one.
That’s as far as I have got. I’m sure there are people out there with some knowledge in the area, so let’s hear from you in the comments. Is there any evidence of harm caused in humans by Bt from GE crops? Enquiring minds want to know!