Researchers from the US National Toxicology Program found that cell phone radiation was potentially linked to a slight increase in the risk of certain types of cancer, in rats Our regular cell phone use focuses the radiofrequency radiation on a small portion of the head but the animals faced exposure to a uniform field across their entire bodies for their entire lives The study looked at three intensities and the rats exposed to all three showed a slight increase in a rare type of heart tumor called a schwannoma from 2.2 percent in the lowest exposure category to 5.