So, now for the negative aspects of GMOs. There are a large number of issues with genetically modified foods, most obvious of which is the health risks. Say, for instance, that you're one of those people that's deathly or insanely allergic to peanuts. If there's a gene from peanuts that's then transferred to soybeans, you might be allergic to GMO soybeans. Because it's a new development, people aren't particularly sure about allergen affects of GMOs. The other possibility is that people may be allergic to GMOs themselves. We don't know for sure the effects they might have upon human health, and introducing something this new will probably bring about unforeseen complications. On the whole, apart from allergenicity, scientists do not believe that GMOs carry any other health risks- however understanding possible existing or new allergens could pose a serious problem.
One easy solution to this is labeling- products now are required to place a blurb somewhere on the packaging saying whether or not they contain nuts, or if they may contain traces of peanuts. If laws and regulations were passed, requiring all GMOs to state that, a) they are GMOs, and b) whether or not they have any peanut genes. It's easy for those who may be allergic to simply avoid the food, just as they do now with other possible dangerous foods.
What I, personally, am more concerned about are the environmental hazards. Most of these I really hadn't thought of until I read this overview of GMOs. One of which would be possible unintended harm to other organisms. A comprehensive breakdown of b. t. corn, found here, helped really explain the issue. B. t. corn is normal corn that's been injected with Bacillus thuringiensis, a bacterium that allows corn to secrete natural insecticide. Scientists have found, however, that this is actually hurting monarch butterfly populations.... but how is that? Monarchs eat milkweed plants, not corn. The fear is that if the pollen from b. t. corn is blown by the wind, and gets mixed in with nearby milkweed plants, monarch caterpillars and butterflies could perish and die unintentionally.
Another concern is that plants genetically modified for herbicide tolerance would possible cross-breed with weeds, resulting in herbicide resistant weeds. It's possible because plants are fertilized via pollen, and cross-pollination could accidentally create "superweeds", which would be an absolute pain in the rear to get rid of. The other issue is that just as some strains of mosquitoes had developed a resistance to DDT, something similar could happen with crops like b. t. corn. If the insects become resistant to the self-producing pesticides, than really what's the point?
One way to sure the issues like the lack of insect discrimination (i.e. accidentally killing butterflies) and potential crossbreeding is to modify the pollen. Either modify the genes of the plants so that they are male-sterile (they just wouldn't produce pollen at all) or modify the genes of the pollen itself to make it harmless. If there's no pollen at all, than that completely eliminates any possibility of contaminating milkweed plants, and harming other insects on accident. Or, if you can modify the genes so that the pollen is just that of normal, average corn, that takes away the risk of "superweeds", and life around the b. t. corn would continue on as normal.
The other idea, that I never would have thought of but is really creative, is to create a "buffer zone" around the b. t. corn. Basically, you'd plant the b. t. corn and surround it with normal, average corn. The average corn would absorb any wind-blown pollen, which would protect the milkweed and prevent "superweeds". Also, the average corn wouldn't be harvested, so insects would be allowed to eat away and destroy the average corn; thus they wouldn't bother with the b. t. corn, preventing insecticide tolerance. Calculated estimates of the necessary buffer zone range from six meters deep to thirty meters deep, so how feasible of an idea this is (in terms of economic and spatial efficiency) really depends upon the necessary amount of a buffer zone. Obviously if it's too high a number, it would be inefficient and not worth it.
There are many issues and concerns about genetically modified food, and while there are many potential solutions, it's going to be necessary for people to work out the kinks in GMOs before they will become a feasible, reliable, and trusted source of food.