I asked Rob today about the difference between old school spray-on Bt and new school genetically-engineered-to-be-a-part-of-the-plant Bt. (See my previous post for some background.)
Here's a concise summary of his opinion: Spray-on Bt is good, genetically engineered Bt is bad.
Here's a more detailed summary:
With spray-on Bt, most of the spray will end up on the leaves of the plant, not the final vegetable eaten by we eaters, and even much of that will be washed away by the rain and cleaning. By the time the vegetable reaches one's mouth, the amount of Bt we might consume is very small.
But in the case of plants genetically altered to have Bt inside of them, there's no dilution of the Bt. We eaters will consume it in a full dose when we bite into that vegetable. Rob said that consuming Bt like this might not make anyone sick in any immediate sort of way, but less is known about what effects eating these GM plants might have over the long term.
In addition, there's an ecological/evolutionary concern associated with Bt being genetically added to crops. In the case of spray-on Bt, it's inevitable that some percentage of plants will get missed during the spraying process, and that some of the bugs that eat these plants will still get their meal and will continue to be healthy and to reproduce. But in the case of crops genetically engineered to have Bt inside of them, there's no variance and thus no chance for ecological checks and balances. Every GM plant will have Bt inside of it, meaning every bug that wants to eat that plant will either have to evolve, die, or go somewhere else. The effect this might have up and down the food chain is unknown and difficult to predict.
(Okay, that was the best attempt by the non-scientist I am to explain something scientific. Any of the ecologists out there want to jump in and correct my mistakes or amplify on these thoughts?)
Rob said something else interesting during our conversation. He said that in Europe the government standard when it comes to altering nature is "Prove to us it's safe." But here in America, the standard seems to be "Prove to us it's not safe."