said by ahhnold:uv is non-ionizing and it causes cell damage and cancer unrelated to "heating". There is simulation evidence sub-millimeter radiation can cause DNA damage due to "nonlinear resonances". Very very low frequency radiation in thousands of meter bands has shown to be a hazard to the human nervous system due to induced currents.
Wifi, cellphone and other radio waves are classified as non-ionizing radiation. Its main interaction effect with biological tissues is heat transfer. No peer reviewed scientific studies have shown evidence to the contrary at current usage/exposure levels.