Bt corn and Bt soybeans are two common crops in the U.S. that have been genetically engineered to produce their own pesticides, using genes from the bacteria called B. thuringiensis.
How scary is a crop that's been engineered to produces its own toxins? An in-depth article by Ferris Jabr in Scientific American argues that it shouldn't be, because these toxins are only harmful to insect pests:
"Numerous laboratory and field tests have concluded that Bt is not toxic to fish, birds, mammals or people, even at doses thousands of times greater than what a person or animal would ever encounter outside the lab. Over the years researchers have injected or piped billions of Bt spores and toxic crystals directly into the skin, lungs, blood, stomachs and brains of mice, rats, cows, pigs, hens and quails; time and again the animals survived the experiments with few, if any, ill effects. The same is true for rats that ate one billion Bt spores a day for two years as well as for three successive generations of rats fed Bt corn."
The article also argues that by avoiding sprayed insecticides, beneficial species aren't harmed:
"Overall, Bt crops around the world have been a boon for all kinds of insects and arthropods because this highly selective form of pest control has greatly diminished the use of chemical pesticides that kill buggy friend and foe alike."
While this article rounds up an impressive amount of research in favor of the use of genetically engineered Bt crops, it makes light of the areas where we lack data, particularly long-term data. Nonetheless, the author is decidedly on the pro-GMO side of the discussion. Are you convinced?