With everything there are cons, as well. Most people consider the biggest concern is that genetically engineered organisms will interbreed with natural organisms. This creates the concern of how they will affect the health of our environment and humans because there is not enough evidence showing how they will affect natural organisms. In agriculture, some fear that widespread crop failure will occur if a virus, fungus, or pests develops and attacks a specific crop because all of the seeds of the crops will be of an identical genetic structure.
Research shows that food that was genetically engineered has resulted in 37 deaths and 1,500 partially paralyzed people. In addition to this, this has led to 5,000 additional people experiencing a temporary disability due to a syndrome, known as Tryptophan, linked to a genetically engineered bacteria.
Of course, there are also ethical concerns and the biggest concern in cloning. Since the first cloning, Dolly in 1996 (died in 2003), the safety of cloning and genetic engineering has been heavily questioned.