[img_assist|nid=107|title=|desc=|link=none|align=left|width=99|height=43]Bt crops were developed about 15 years ago, and there still is no method to properly assess the toxin content of plant material.
The first two varieties Bt176 and MON810 were approved for cultivation more then a decade ago. Appication documents asking for approval of Bt crops in the EU usually contain some information about how much Bt toxin at least some of the different tissues contain at one or several dates in the cultivation season. On the other hand, measuring protein concentrations using a method as old as ELISA appear to be just a normal thing to do. So one would expect that it would be possible to measure Bt concentrations in the Bt maize MON810 grown in the EU.
Well, it appears that it is possible to measure it, but there are a number of different ELISA kits and protocols available - and they simply come to different results. So there is no comparable way of testing Bt contents of different samples, and at the same time the Bt concentrations vary so much, that it really seems to be necessary to measure the contents. That is a result of a study that the Swiss lab Ecostrat undertook for a second year for Greenpeace.
And not only Greenpeace comes to the conclusion that this is enough reason to hold the cultivation of new GM crops. EU Environmental Commissioner Dimas for the first time decided to propose not to give approval for two GM crops, Bt11 and 1507 maize. Referrring to a different study, financed by the Germany ministry for research the draft Commission Decission states: "Recent studies (Nugyen & Jehle 2007) indicate that there is both a high variation of toxin concentrations between plants on the field as well as statistically significant differences between different locations in Germany, where the studies have been conducted. The reasons for such differences in the plants and in the locations as well as the range of variation are not yet identified and may lead to unpredicted interactions with the environment that could cause adverse effects."