The head of a cancer research center is urging his faculty and staff to limit their cell phone use.

Dr. Ronald Herberman of the University of Pittsburgh Cancer Institute is worried about the possible risk of brain cancer. He says there's a "growing body of literature" linking long-term cell phone use with adverse health effects, including cancer. He's basing his warning on early, unpublished data.

Herberman is urging his faculty and staff to keep cell phones away from their heads, and use the speakerphone or a wireless headset. He says children should use cell phones only for emergencies.

Experts with the American Cancer Society tell 11 News there is not enough proof to link cell phones with cancer.

"There's been multiple studies done on the link between cell phones and cancer and to date there's really no proof and studies that has come out and linked the two together," said Lisa Bade, Communications Director with the American Cancer Society.

Other researchers point to numerous studies which have found no link between cell phone use and brain tumors. The Food and Drug Administration says if there is a risk it's probably very small.