Gov. Matt Blunt signed a bill ... prohibiting companies in Missouri from forcing workers to have microchips implanted in their bodies. You read that right. In Missouri, it's now illegal for businesses to require employees to have a microchip embedded under their skin. When you're forced to have a chip put in you as a condition of employment, that's taking away your civil liberties and your freedom," said Rep. Jim Guest, a King City Republican. Guest added the microchip language to a bill concerning overtime and disability benefits. Next year, he said, he will introduce a bill to prohibit all microchip implants in humans. Only a few hundred people nationwide have been voluntarily implanted with the devices, and mandated microchips are virtually unheard of in Missouri or anywhere else. But three other states already prohibit mandatory implants. Guest ... said it's crucial to ban the technology before it gains any traction. "We want a law on the books so we can stop a major problem before it starts," he said. Privacy advocates and others worry that widespread use of such chips could allow individuals to be tracked or monitored without their knowledge and create identity theft issues. The chips, which use radio frequency identification [RFID] technology, are about the size of a grain of rice and are usually implanted in the upper arm. Guest and others have raised health concerns as well, citing studies that link implanted chips with cancerous tumors in laboratory animals.