We tried to mimic a high level of exposure that humans might experience, said study leader Dr Joseph L Roti Roti, professor of radiation oncology, of biochemistry and molecular biophysics and of cell biology and physiology.

We found no statistically significant increases in any tumor type, including brain, liver, lung or kidney, compared to the control group.

The study used 480 male and female rats. One third of the animals were exposed to the analogue cell phone frequency, one-third to the digital frequency and one-third served as controls and received no radiation.

After two years and a total of 505 days of exposure, the brain, spinal cord and other organs from each animal were studied microscopically for signs of cancer.

We looked specifically for brain and spinal cord tumors, said Dr Marie C La Regina, a veterinary pathologist with the University’s Division of Comparative Medicine and the lead author on the study. We examined 20 to 25 sections from each brain microscopically, which is more than is usually done when studying potential cancer-causing agents. We didn’t want to miss anything.

As far as I can tell from the work so far, said Dr Roti Roti. The greatest hazard with cell-phones is driving a car while talking on one.