Difference engineWorrying about wirelessTechnology and society: Concerns about the danger posed to human health by radio waves are misplacedand increasingly irrelevant. The use of phones while driving is far more likely to cause harmSep 3rd 2011 | from the print editionALTHOUGH the myth that mobile phones cause cancer has been laid to rest, an implacable minority remains convinced of the connection. Their fears have been aggravated of late by bureaucratic bickering at the World Health Organisation (WHO). Let it be said, once and for all, that no matter how powerful a radio transmitterwhether an over-the-horizon radar station or a microwave towerradio waves simply cannot produce ionising radiation. The only possible effect they can have on human tissue is to raise its temperature slightly.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 spectrumalong 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 atomsbreaking chemical bonds and producing dangerous free radicals in the process. It is highly reactive free radicals that can damage a persons 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.All of which leaves doctors more than a little puzzled as to why the WHO should recently have reversed itself on the question of mobile phones. In May the organisations International Agency for Research on Cancer (IARC) voted to classify radio-frequency electromagnetic fields (ie, radio waves) as a possible carcinogenic to humans based on a perceived risk of glioma, a malignant type of brain cancer.A year earlier, after a landmark, decade-long study undertaken by teams in 13 countries, the IARC had reported that no adverse health effects associated with the use of mobile phones could be found. As for the heating effects of radio waves, the increase in temperature of the skin caused by holding a phone close to the ear was found to be an order of magnitude less than that caused by direct sunlight.The Group 2B classification the IARC has now adopted for mobile phones designates them as possible, rather than probable (Group 2A) or proven (Group 1) carcinogens. This rates the health hazard posed by mobile phones as similar to the chance of getting cancer from coffee, petrol fumes and false teeth.That has not stopped the tinfoil-hat brigade from continuing to believe that deadly waves in the ether are frying their brains. Lately the paranoia has spread to the smart meters being introduced by electrical utilities in various parts of the world. Smart meters are