The city of San Francisco is now requiring cell phone vendors to post the radiation level emitted by each phone.

The city board approved the measure based on a recent study that shows the chance of getting a brain tumor significantly increases after a decade of cell phone use. However, other studies have shown little or no link between the phones and cancer.

Cell phone companies aren't happy with the decision and insist their products are safe.

"The Wireless Association, the Federal Communications Commission set standards, very stringent standards, for what's called specific absorption rate. And every device in the United States has to operate at or below that level," John Walls, with the International Association for the Wireless Telecommunications, said.

"If there's any possibility, the slightest possibility, that it could be harmful to anyone, I think we have a responsibility to do what we can," Sophie Maxwell, with the San Francisco Board of Supervisors, said.

San Francisco is the first city in the country to pass any measure regarding cell phone radiation. There is no word if other cities will follow.