Page "Electromagnetic radiation" Paragraph 80

The World Health Organization has classified radiofrequency electromagnetic radiation as a possible group 2b carcinogen.

This group contains possible carcinogens with weaker evidence, at the same level as coffee and automobile exhaust.

For example, there have been a number of epidemiological studies of looking for a relationship between cell phone use and brain cancer development, which have been largely inconclusive, save to demonstrate that the effect, if it exists, cannot be a large one.

See the main article referenced above.