Mobile phones: is there a brain tumour risk?

Media reports linking brain tumours to the use of mobile phones have surfaced again, with claims of a “brain tumour pandemic” unless people change their patterns of mobile phone use. So what's the real risk?

The latest claim was made by Lloyd Morgan, a researcher for U.S. campaign group, the Environmental Health Trust, who says previous studies “underestimated” the cancer risks. His research has not been published in a scientific journal, but was released at a conference in Seoul, South Korea on 10 June 2010. It has been widely reported today, including in the Daily Mail and Daily Telegraph.

Morgan's claim comes in the wake of a much wider study by the World Health Organisation published in May 2010, called Interphone, which looked back over many years of mobile phone use across different studies in many countries.

The Interphone study found small associations with some brain tumour types, but the authors acknowledged that the biases in these studies make it difficult to say there is actually a risk.

Brain Tumour UK regularly reviews the scientific evidence on the potential health risks of mobile phone usage.

The radiation from mobiles is called non-ionising, low-frequency radiation, and is quite different from the ionising, high-frequency radiation from, say, X-ray machines.

Mobile phone radiation is thought to be insufficient to break genetic bonds and cause brain tumours to occur. However, some scientists think there could be a risk to children or from long-term use of mobiles and are trying to assess that risk.

Measuring risk is difficult. Nobody wants to expose real children or adults to increasingly high levels of radiation - that would be unethical.

Another problem with these studies is that they can easily be biased.

One kind of bias is called recall bias. It is really hard to remember, accurately, how many minutes a day you used your phone five or ten years ago. Another problem is selection bias. Studies which include people with brain tumours are more likely to get biased answers if they tell those people that the study is about mobile phones and brain tumours.

This doesn't mean that mobile phones are in the clear. It's just that, right now, we don't have an easy way of explaining how mobile phones could cause cancer or of measuring their impact - if there is any - without bias.