My work is focused more on social and environmental research as opposed to health research, although I am familiar with the literature--and it's an emerging literature around associated health impacts.
Initial studies indicate that there could be potential issues. Allergenicity is one that has been looked at. I have heard of these respiratory issues specifically in communities growing Bt products. The bacillus thuringiensis appears to, in some of these initial studies, have potential respiratory impacts, but all of this stuff is not conclusive. I think it points to the need for more research around health issues related to the introduction of genetic engineering.
Once again, this is a new technology. The way in which we regulate it says that these crops are substantially equivalent to conventionally bred crops. The national research centres in the U.S. are saying that even for conventionally bred crops, as well as genetically engineered, we need to reassess how we study these things, because there can be these additional health issues associated with any type of biotech, traditional or modern, and it requires a whole new way of thinking around this. It empowers the research community to go out and ask those hard questions and try to find out more information.