The Agriculture Department has given a preliminary green light for the first commercial production of a food crop engineered to contain human genes, reigniting fears that biomedically potent substances in high-tech plants could escape and turn up in other foods. The plan ... calls for large-scale cultivation in Kansas of rice that produces human immune system proteins in its seeds. The proteins are to be extracted for use as an anti-diarrhea medicine and might be added to health foods such as yogurt and granola bars. Critics are assailing the effort, saying gene-altered plants inevitably migrate out of their home plots. In this case, they said, that could result in pharmacologically active proteins showing up in the food of unsuspecting consumers. Although the proteins are not inherently dangerous, there would be little control over the doses people might get exposed to, and some might be allergic to the proteins, said Jane Rissler of the Union of Concerned Scientists. This is not a product that everyone would want to consume," Rissler said, adding that other companies grow such plants indoors or in vats. "It is unwise to produce drugs in plants outdoors."