Sales increased in the wake of fears that electromagnetic radiation from the mobile could affect brain tissue.

BBC: Hands-free mobiles given safety boost

While an increased risk of brain tumors is not established, the increasing use of mobile phones and the lack of data for mobile phone use over time periods longer than 15 years warrant further research of mobile phone use and brain cancer risk.

CNN: STORY HIGHLIGHTS

In February, a study by researchers at the National Institutes of Health, revealed radiation emitted after just 50 minutes on a mobile phone increases the activity in brain cells.

CNN: WHO: Cell phone use can increase possible cancer risk

There are ongoing efforts by cognitive science laboratories and companies to develop cognitive assessment and brain training software that will function on mobile phones and tablets.

CNN: How mobile tech can influence our brain

And that would be enough to account for the fact that several of the single-country studies found that ten years' mobile use was associated with an increased risk of brain tumours on the side of the head that people said was exposed to their handsets.

ECONOMIST: The Interphone study: Mobile madness | The

Hands-free mobile phone kits can significantly reduce the effects on the brain, according to research.

BBC: Hands-free mobiles given safety boost

Both found, as one put it, "the data do not support the hypothesis that mobile phone use is related to an increased risk" of brain tumors.

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In hospital interviews, brain tumor patients were asked to answer a series of questions based on memory about their mobile phone use habits prior to being diagnosed.

CNN: Study fails to end debate on cancer, cell phone link