THE ECONOMIST on cellphones and cancer:

In the real world, the only sources of ionising radiation are gamma rays, X-rays and extreme ultra-violet waves, at the far (ie, high-frequency) end of the electromagnetic spectrum—along with fission fragments and other particles from within an atom, plus cosmic rays from outer space. These are the sole sources energetic enough to knock electrons out of atoms—breaking chemical bonds and producing dangerous free radicals in the process. It is highly reactive free radicals that can damage a person’s DNA and cause mutation, radiation sickness, cancer and even death.

By contrast, at their much lower frequencies, radio waves do not pack anywhere near enough energy to produce free radicals. The “quanta” of energy (ie, photons) carried by radio waves in, say, the UHF band used by television, Wi-Fi, Bluetooth, cordless phones, mobile phones, microwave ovens, garage remotes and many other household devices have energy levels of a few millionths of an electron-volt. That is less than a millionth of the energy needed to cause ionisation.